# Bad hesitation



## fineline (11 mo ago)

Not that I've ever had a good hesitation .. anyway. I've been struggling now for several years (to my shame) with a severe hesitation when you step on the gas. It feels like it's almost going to cut out for a moment, then it picks back up.
I've adjusted timing back and fourth. I'm not sure where to go with that as my timing light argues with my vacuum gauge.
I searched for vacuum leaks (I think it possibly still has one but if it has, I can't find it). 
I Fitted a fuel pressure gauge which was helpful. I even fitted a wideband 02 sensor and gauge which was handy for dialing in cruising mixture ratio but only serves to confuse me more when it comes to the bog.
I think I should go back to basics and start again. but I feel a little beaten by this.
Going through the previous owners paperwork of 7 plus years ago... this is what's in it.
Thanks in advance! 

1970 Pontiac 400 Engine
Edelbrock Performer RPM round port cylinder heads. 72cc Intake 2.110 Exhaust 1.660
Comp Cams CCA-SK51-222-4 Hydraulic flat tappet cam duration, 262/270. Lift, 462/470
Keith Black Flat top forged pistons
Scat 4340 Forged H beam rods
Holley 770...I think?


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## armyadarkness (Dec 7, 2020)

There are so many serious variables... most likely carb.


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## fineline (11 mo ago)

That's true. My gut feeling says it's the carb too. Trouble is there seems to be a bit of voodoo involved with carbs. 😕


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## Maczuga (Sep 16, 2020)

Not very familiar with aftermarket engine upgrades but I would point out two things, one, the carb itself, that is looking for vacuum leaks - try spraying e.g. carb cleaner, plastic reconditioner in aerozol etc. around and look for engine respond, also hook up a vacuum gauge and look if the reading is rather steady or jumping around on different rpms. What is the reading on idle? Are you having starting problems? Does the electronic choke disengage after warm up? You may have some passages clogged up and/or internal parts gumed up that restrict proper fuel flow or even sth. missing. 
Secondly the ignition - are you running mechanical or electronic? It may be the timing that is messing up your acceleration. Try hooking up a decent electronic timing light and rev the engine while checking the reading. Note the timing advance and try looking up a chart on the internet with the proper relation of advancement degrees to rpms.
By any chance try to find out if the existing build was finished by the previous owner and that he didn't drop it after he couldn't figure out how to get the engine properly to work.

Hope I could point you to useful directions.

Good luck


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## Lemans guy (Oct 14, 2014)

Is it a bog from stop, like taking off from a red light…or is it a bog at cruise, say accelerating from 40 to 50MPH?


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## fineline (11 mo ago)

Thanks Maczuga. I did try spraying carb cleaner around the intake and carb but couldn't say for sure if it changed rpm. The clutch fan didn't help much with that.
I had disconnected the vacuum advance about 2 years ago and left it like that, as my idle was too high even with the idle screw all the way out. 
My timing light shows me 12% BTC at idle (800 rpm ish, it does fluctuate after revving). and 36% total which after some research seems ok.
I then connected my vacuum gauge which indicated 15Hg which stated on the gauge "late ignition timing". Not sure if I should be paying attention to that part? when I retarded the ignition more, I was able to get the vacuum to 18HG and in to the "normal" range on the gauge, but my idle was too high now. 😕 
The choke seems to be working ok.
The distributor is an HEI 
Unfortunately I don't have any contact details for the previous owner.
I can give the carb a strip down and clean up, could be worth a shot.


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## fineline (11 mo ago)

Lemans guy said:


> Is it a bog from stop, like taking off from a red light…or is it a bog at cruise, say accelerating from 40 to 50MPH?


It's definitely more from a stop,. from 40 to 50 mph it would be ok.


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## Maczuga (Sep 16, 2020)

Assuming that the new carbs I am not familiar with operate the same way as the oem, as far the high idle goes, it seems to me almost like a problem to the idling passages inside your carburetor, either they are clogged up or simply bypassed due to insufficient vacuum, too wide open throttle and or bad adjusted idle screws. The hesitation can be related to the accelerator pump or a missing check ball or both and or clogged passage, filter screen, insufficient fuel level in the bowl and maybe even fuel pressure.

I had on my factory low mileage 389 engine a similar issue with the high idle. As it turned out the main problems were the vacuum leaks at the base plate of my Rochester carburetor that made the previous owner pull out the idling screws far beyond reason. Along with those operations engine timing and engine dwell went off too.

What I started with was a vacuum gauge and a good timing light (hard to come by if you live in Europe, I know that by myself ). First I cleaned the whole carburetor and looked for parts needing replacement, swapped the gaskets, checked the distance of the air horn upper edge related to the base plate of your intake manifold - thickness of the gasket you install relates to the vacuum inside the carburetor! After reassembling, setting the idle screws to default. Are there any more adjustment screws on your carburetor?
Next I would go for the engine dwell (assuming you can change it on your electronic points) and check if it's good. Then move over to engine timing and try adjusting it - be aware that a) idling speed is necessary - I believe any rpm's below 1500 are the way to go at this stage, otherwise the centrifugal weight advancement inside your distributor will play games with you  b) if you have it, vacuum advance tube on the distributor is disconnected and plugged - the same game as above.
After being sure that engine timing is correct, check again dwell because timing affects it. Now having timing and dwell set correctly go back to your carburetor and hook up a vacuum gauge to a free port. With any adjustment screws (fuel mixture, air mixture etc. your carburetor might have) try to achieve the max highest vacuum reading. Once that is, try to lower your rpm with the speed screw (if you have one). Repeat this process several times until you achieve the lowest possible rpm in relation to the highest vacuum reading. After that you should be almost finished, just check if you can rich out (more fuel, less air) the mixture without further vacuum drop - you don't want to run your engine warmer than it is necessary. If you have any external add-ons like an anti stall diaphragm (dashpot) - ajdust them at last.

I couldn't figure out for long what my idle problem was (after replacing parts and checking everything) until I realized that my tools were faulty. I had a UNI-T professional automotive multi meter that measured rpms and dwell and as it turned out, the multi meter couldn't properly count engine rpms on an 8 cylinder After I bought my timing light (in this case Innova Pro, but I believe there are many more) it turned out that my multi meter showed some 300+ rpms more then in reality there were. That is why I kept detuning all the time my carb 

As I said earlier, I am by no means and engine expert and take all of my advise with reserve.
I am sure with your given information, should the problem still persist, some smarter folk here will help you.

Anyways, I hope I could help you at least a bit.

Wish you success!


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## fineline (11 mo ago)

Wow thanks for all that info Maczuga! 
Dwell angle? I've heard of it, but I'm going to do have to do some research on that to learn more about it. I'll have a look at some of things you mentioned, starting with a carb clean and a carb gasket check. I have some spacers under my carb.
I've always wanted a good timing light but have somehow managed to end up with 3 not so good timing lights.
Here's some pics of the offending area. It may not show much but you never know, and it's something to look at.


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## Sick467 (Oct 29, 2019)

Bad accelerator pump diaphragms can cause a stumble or bog from a dead stop to low speed. The moment you start to push the gas peddle, the accretor pump should give the engine a extra squirt of gas. This raises the rpm to handle the added power the engine needs to get off of the dead stop. After that, other gas circuits feed the engine. Without a functioning accelerator pump, the engine is relying on the idle circuit and the cruise circuit to do the work from a dead stop to 5 -10 mph causing the bog until the cruise circuit kicks in.

Like Army said, there can be many causes for this, but the accelerator pump is the one that straightened my hesitation out.


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## fineline (11 mo ago)

Thanks Sick467. I did notice when the engine was off but still hot, and the air cleaner was off. When I gave the carb a pump, I saw steam come from the carb so the pump is doing something, just not sure how much it is or isn't doing. I did try and clamber over the top to see if it was a good solid squirt but I just couldn't see properly. I'll have to have another go at that.


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## Sick467 (Oct 29, 2019)

I do know that an accelerator pump can be squirting, but be squirting an inappropriate amount and cause problems. I think Holley's are adjusted by swapping out the pump cam. The trick will be figuring out if it is squirting lean or rich...both can cause the hesitation. A lean event might produce a bog and then a gradual recovery (the engine starves for fuel, then bogs, and then starts to get it back), where a rich event could be a bog and a more powerful recovery (the engine begins to flood and bogs from too much squirt and then catches up and wants to surge) . Just my two cents as I am not a carb guru.

It's a pretty good rule of thumb to get the ignition/timing as good as you can before messing with the carb. I did rebuild a Holley last summer that looked similar to yours and it was a good experience. I used a book by Mike Mavrigian called "Holley Carburetors: How to Rebuild". This book is a good guide. My personal opinion is that it needs to be revised as it seems to have some steps out of order and jumps around a bit, but it was very, very helpful to me since I had never rebuilt a Holley before.


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## Lemans guy (Oct 14, 2014)

Lot’s of solid advice from the gang. Many things to consider and all valid. First your bog, you said no bog at speed like going from 40 MPH to 50 MPH, this is where the accelerator pump comes in also.

However a bog from full stop is often because the transfer slot, which is in the carb barrel right at the throttle plate is set wrong. Usually the slot is already wrongly fully exposed under the throttle plate and therefore does not work.

The idle circuit has round feeds that come in below the plate but also has a slot that is there to transition from stop to go. It comes on before the accelerator pump, as the accelerator pump takes more throttle, and at the point the transfer slot is already passed.

so turn over the carb, and look for the slot adjust it to a square hole below the plate. More of it will then appear above the plate. And notice while turning the throttle screw on the bench that just a slight turn will open it up. You can make it a little off square but not much. Put it back and reset the idle with the mixture try to leave this throttle screw to very minor adjustments.

when it is too exposed it also makes your mixture screws not work good because it takes there place and feeds the mixture.

it could be other things as the gang mentioned, a lean bog, a vacumn leak, dirty carb, floats etc…but check this first. Let us know how you do!


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## Lemans guy (Oct 14, 2014)

PS go back to 12 degrees and 36 total on timing….15 HG is OK at idle, retarding that timing is not really helping.


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## fineline (11 mo ago)

Thanks Guys! There's now plenty for me to investigate for sure. When it stops raining (yes it's outside adding to the patina ) I'll check some of those things out and keep you posted.
Yes I must nail that ignition timing first too!
Thanks again!


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## fineline (11 mo ago)

Lemans guy said:


> PS go back to 12 degrees and 36 total on timing….15 HG is OK at idle, retarding that timing is not really helping.


Ah ok great! I had a feeling the timing light should outrank the vacuum gauge on that one.


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## PontiacJim (Dec 29, 2012)

fineline said:


> Ah ok great! I had a feeling the timing light should outrank the vacuum gauge on that one.


*fineline, *"I had disconnected the vacuum advance about 2 years ago and left it like that, as my idle was too high even with the idle screw all the way out."

PJ: - RECONNECT THE VACUUM ADVANCE ON THE DISTRIBUTOR to a manifold vacuum source, then redo your initial timing, timing curve, total timing. Then go after a carb problem if it exists.


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## fineline (11 mo ago)

Thanks PontiacJim. Ah ok so I re-connect the vacuum advance to the distributor, even for doing the timing adjustments?


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## Baaad65 (Aug 29, 2019)

You need to have the vacuum advance disconnected and carb port plugged then set your initial and mechanical advance, the vacuum advance only comes into play at idle or whenever the throttle plates are closed then it will pull vacuum advance.


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## fineline (11 mo ago)

Ok thanks Baaad65!


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## Baaad65 (Aug 29, 2019)

fineline said:


> Ok thanks Baaad65!


I went through the bad hesitation thing this summer but it was in the secondary's so a different accelerator cam fixed it, I'm far from the expert here so listen to them and you wont go wrong. Like they said most carburetor problems are ignition problems in disguise.


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## PontiacJim (Dec 29, 2012)

fineline said:


> Thanks PontiacJim. Ah ok so I re-connect the vacuum advance to the distributor, even for doing the timing adjustments?


Vacuum line disconnected as *Baaad65* pointed out when you set your Initial Timing, Timing Curve, and Total Timing. BUT, when you re-connect the vacuum line, your Initial Timing should advance.

The consensus seems to be to have your Initial around 19-21 with the vacuum advance connected.

We have covered ignition timing in a number of previous posts. If you do a search above using the "Search Community" search engine you should be able to pull up several of the posts were we explain what to do.

The engine should run smooth at the 19-21 degrees advance with the distributor vacuum connected. Your idle may increase, but you should be able to bring it back down using the idle speed screw on the carb.

Your carb adapter/spacer could also be some of the problem. Not sure what it looks like - an all open adapter or a 4-hole adapter. If open, it could be causing turbulence or you could be losing air flow velocity when the carb is popped wide open causing a stumble. Stumble from a dead stop is usually a sign that you need more fuel to be pumped into the carb by the accelerator pump and the gas squirters. You may be sucking too much air and not getting enough fuel in with it, so it bogs. 

Some bigger cams will idle higher than stock - But my personal opinion is that you may have gone too small on the cam for your set-up.

Start with the timing, then the carb.


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## fineline (11 mo ago)

Thanks for that PontiacJim, One of the problems I had was the idle was already too high even before the vacuum advance is re-connected. And the idle screw is already out as far as it can go.
From memory the carb spacer was fully open. I could try removing that and see what happens. I recall looking at the intake holes on the manifold and thinking they were smaller than the butterflies on the carb, which maybe why there's a spacer. I'll have to have another look at what's going on there. If it ever stops raining. 😕


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## PontiacJim (Dec 29, 2012)

fineline said:


> Thanks for that PontiacJim, One of the problems I had was the idle was already too high even before the vacuum advance is re-connected. And the idle screw is already out as far as it can go.
> From memory the carb spacer was fully open. I could try removing that and see what happens. I recall looking at the intake holes on the manifold and thinking they were smaller than the butterflies on the carb, which maybe why there's a spacer. I'll have to have another look at what's going on there. If it ever stops raining. 😕


OK, I looked more closely at your pics.

I am going to say you have mis-matched parts.

I see a stock cast iron intake manifold? This would mean the intake manifold is for the Q-jet carb. Then I see an aluminum adapter and then the phenolic heat spacer.

The carb may be the Holley 750, but is it a vacuum operated secondary opening or a mechanical secondary opening?

The heads are probably too big in my opinion as they flow 280 CFM's versus the stock heads that flow around 206 CFM. The smaller passages of the stock head keep air velocity up versus the bigger ports on the E-heads which could make it a little less responsive on the bottom end and picks up at the mid and higher RPM's.

The cam is extremely small in my book and being a Comp Cam on a 110 LSA, the engine will pull good on the lower and mid RPM range and then the power will fall off sharply.

I see what looks like your PCV valve in front of the carb with a hose going? You want the PCV valve functioning and hooked to the carb.

My suggestions are to either go back with the Quadra-jet carb or get an intake manifold that works with the square bore base of the Holley. Get rid of the adapters/spacers.

Make sure the PCV valve is connected to a vacuum source like the carb and that is is working.

Get a different valve cover breather. That one looks like a Mopar unit. I would get one that has more exit opening so the pressures in the engine can easily be pushed out. Too high of internal pressures can pop up your dipstick or even cause the rear main seal to leak/fail. The PCV valve draws vacuum at lower RPM's to pull this pressure out (as well as moisture/fumes), but the breathers do the job at higher RPM's when the PCV valve can't.

My guess is also that the stock intake has not been port matched? The intake ports on the Edelbrock heads have the RA IV size ports which are bigger. The smaller ports will choke down airflow, but may be OK as the smaller ports will also develop more port velocity which could help the heads flow better at lower RPM's.

I would want to make sure you have the correct intake gaskets so there is no leaks if a mismatch causes this. You may be OK, but do look to make sure no leaks. Double check the torque on the intake bolts as they can loosen up and not many check this after the engine has first been broken in.

The idle mixture screws are not the same as the idle speed screw. I am not a Holley carb guy, but here is a picture of a 750 CFM carb. No.1 screw is the idle speed screw which raises/lowers your engine RPM's. No. 2 is the idle mixture screws - one on each side.

Hope this helps.


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## Baaad65 (Aug 29, 2019)

Agreed you need to address those issues pointed out and also is your throttle cable taut because it looks like it's sagging. Did you adjust your accelerator pump correctly? with the carb fully open you should be able to slip a.007 feelers gauge between the pump actuator arm and the head of the adjuster screw, any more slop and you will get a late shot of fuel causing a hesitation, to tight and you'll wreck the pump diaphragm When you get your timing set correctly and the issues PJ pointed out then you can start fine tuning the carb with different cams and squirters, power valves and jets.


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## fineline (11 mo ago)

Thanks so much for that detailed reply!

It is a stock cast intake manifold. Funnily enough I was googling last night for an Edelbrock performer intake...wow the prices have gone up! I used to have one a few years ago but I gave it to a fellow pontiac guy in need. Silly me. 
I'd prefer to go the new intake route than quadrajet as they mystify me even more and I like the light weight aluminium intake.  I'll keep searching for another Edelbrock performer I think.

The carb is a vacuum secondary. I have an old holley double pumper in the attic gathering dust...

You're right the car has more bottom end grunt than top end. Though I don't mind that too much.

The pcv valve is connected to the manifold vacuum, I took that out last week to clean and check it, all seemed good. I thought it being connected to the manifold is ok, or would the carb be better?
The brake booster is also connected to the manifold. just near it, but from a different port. Can't quite see from the photos.

I'm not sure what breathers would be better than these? There's 2 of them so I have stereo breathing. I've not had the dipstick pop out on this engine.

I happened to check the intake bolts recently and most seemed ok though a few center ones weren't as tight as they should have been. With the tightening sequence I wonder if I should have loosened them all first before re torqueing?

looking at my 02 gauge the carb is still running a bit rich at idle even though I have adjusted the mixture screws to 1 turn out..

Thanks also Baaad65 There's a little slack on the throttle cable as I did everything I could to lower the idle speed.. If I push the throttle closed the idle speed does drop a little more.
I'll check the fuel pump with a feeler gauge and re do the ignition timing today as it's finally stopped raining.

Just in case it helps, when I really accelerate hard, you get a real whiff of fuel afterwards...

Thanks again guys I'll keep you posted.


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## Baaad65 (Aug 29, 2019)

I'm running an Edelbrock Performer RPM but there are other brands of intakes out there also maybe cheaper, I think it's the air flow like PJ said and all the spacers contributing to the problem. I have an 850 Quickfuel DP with an open 1/2" phenolic spacer but I should have probably went with the four hole after researching it. Check the actual area of flow in the breathers as they may look ok but are really not, I bought some and they had tiny holes which I had to drill out and look into a Wagner adjustable PCV it's well worth it. I can't remember your compression or octane you're using but make sure you're timing is up there as long as you don't have detonation or over heating. And remember one change at a time then check things, I bought a good book on tuning which really explains things and helped me, it's from FBO ignition at 4secondsflat.com and the site has a lot of good information especially on reading plugs. Where are you smelling the fuel under the hood, in the cockpit or out the tail pipes? Maybe it's pooling on the spacers or a flow issue again? How do the plugs look?


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## fineline (11 mo ago)

Thank you Baaad65! I'll try and take a pic of the breathers. I've never heard of an adjustable PCV valve, I'll have a look at those.
I've never checked the compression, whenever I do that on an engine I end up in a machine shop getting a re bore.  . Yes good point on 1 change at a time.
I can smell the fuel in the cockpit after I mash the peddle.
I just had a look down the carb when I throttle and it's more of a dribble than a squirt.
I tried to adjust my fuel pump (on the carb) using the feeler gauge but I seemed to squash the spring way too much, it just didn't look right. (still some pump movement on the feeler gauge though). So I backed it off again just so the slack is gone, but on full throttle there's plenty more pump movement to be had. Maybe a change of pump cam then? or pump cam position?.
The plugs are slightly tanned on the electrodes with a touch of black around the threaded ends.


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## Baaad65 (Aug 29, 2019)

Well I don't think you should be smelling gas in the cabin if you accelerate when it's running or not running unless something is leaking. Look up some videos on accelerator pump adjustment but if it's only a dribble when you rotate the throttle shaft quickly there's a problem, it should be a strong stream. Either it's way out of adjustment or the pump diaphragm is ripped or there's something clogged in the carb. Here's the Wagner it's pricey but not as much as replacing a rear main seal. Breathers before and after ,Army loves these pictures 🤣


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## fineline (11 mo ago)

That's a serious PCV valve! I like it!.
Fuel smell in the cabin is strange, but I don't think I have a leak anywhere.
I'll have another look at that fuel dribble/squirt to confirm it was what it seemed.

I set the timing at 10% or12% idling at about 800rpm ish. Idle speed seems to change speed a little every time you throttle it.
And 36% total timing. Then I plugged my vacuum advance back in and it idled at 2000rpm. I don't think I had any more adjustment out on the idle speed screw. So I unplugged it again.


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## Baaad65 (Aug 29, 2019)

Better keep a fire extinguisher handy, if you check the timing then with the vacuum advance plugged in you can tell what the can is giving you, probably need a limiter so you only pull about 10° that's what I'm doing on the advice of the experts her. I'm just relating my experience from a lot of help here, reading good books and trial and error, be careful with the internet information.


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## PontiacJim (Dec 29, 2012)

fineline said:


> That's a serious PCV valve! I like it!.
> Fuel smell in the cabin is strange, but I don't think I have a leak anywhere.
> I'll have another look at that fuel dribble/squirt to confirm it was what it seemed.
> 
> ...



It is quite possible that the HEI is advancing too much when you reconnect the vacuum line. The idle will increase as timing is advanced, but not go from 800 to 2,000.

Check your timing at the balancer when you hook up the line. You only want around 10-12 degrees of advance from the distributor's vacuum advance. In this way, you can set Initial timing at idle without vacuum to 10-12 degrees and then connect the line and it should jump up to 20-22 ish.

Keep at it, but it may be a few things that will need to be addressed. Found a lot of info on adjusting the 750 Holley - the primary throttle blades should have a .040" gap when closed by the idle screw, so it is basically factory set and backing it out won't close the blades completely - so .040" is it. The idle mixture screws on each side allow air/fuel into the carb, so they have to be set accordingly and I believe I read the screw setting is 1 1/4 turn out to start. These screws can affect idle speed. One blog mentioned an O-ring inside the fuel plate the idle mixture screws go into and if missing will let air enter and raise idle speed. You may have a stop/adjustment on the secondary throttle plates. If not adjusted correctly, it could be holding the secondary plates open just a bit and causing higher idle.

It was also suggested to remove/plug all your vacuum lines that go to the carb - like the power brake booster/PCV line to make sure they are not causing a vacuum leak. And, one person found he used the wrong intake gaskets as the heads had larger ports, intake had smaller ports, and the vacuum leak was at the top of the gaskets as they did not seal well enough - which I pointed out. Stock ports are 2.05" x 1.13"; and the RA IV ports are 2.18" x 1.16" and the recommended Edelbrock intake gaskets are just a bit larger at 2.20" x 1.18". Not saying you have a problem, but keep this in mind if all else fails in getting the engine to run well. 

Check out a few of the YouTube video's on the Holley and that may give you some help on adjusting it.


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## Baaad65 (Aug 29, 2019)

Listen to the expert 👍


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## fineline (11 mo ago)

Thanks guy! I should have read the timing with the vacuum advance, I'll do that next time.

I'm researching up on the holley carbs and watching some good videos. Waiting for that eureka moment.

I even made myself a piston stop to check the timing mark was accurate and it was.

I'll plug and re check the vacuum lines too.
I had tried to use carb cleaner to check for vacuum leaks but the clutch fan doesn't make it easy.

I'll save the intake gasket check for later or at least until I have another intake. 

I'll keep attacking this until either it breaks or I do. Or maybe I get evicted...With it's 4" pipes, that thing is loooud!


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## Baaad65 (Aug 29, 2019)

fineline said:


> Thanks guy! I should have read the timing with the vacuum advance, I'll do that next time.
> 
> I'm researching up on the holley carbs and watching some good videos. Waiting for that eureka moment.
> 
> ...


Holly crap 4 inch! Why so big ?


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## Baaad65 (Aug 29, 2019)

Here's a link to my carb reaction after I fixed the hesitation, that's how the pump nozzles should work 👍carb exhilaration


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## Baaad65 (Aug 29, 2019)

Another one I had.February 19, 2022


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## fineline (11 mo ago)

Baaad65 said:


> Holly crap 4 inch! Why so big ?


That's one sentence I'd never thought I'd hear.  
The car came that way. I have to admit I do like the sound. It's a real safety feature, as you can be heard in about a 3 mile radius.
Just checked out those links. That sounds healthy. I'm hoping to hear just that, some time soon...


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## Baaad65 (Aug 29, 2019)

Just made mine louder 👍


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## Baaad65 (Aug 29, 2019)

# 2


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## fineline (11 mo ago)

That sounds fantastic! Maybe when I've fixed my running issue I'll get some cut outs. Always been tempted..


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## Baaad65 (Aug 29, 2019)

fineline said:


> That sounds fantastic! Maybe when I've fixed my running issue I'll get some cut outs. Always been tempted..


Well I think you'll have to reduce down for them because 3" is as big as I've seen them.


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## fineline (11 mo ago)

And to be honest I guess it's plenty loud enough as it is.


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## fineline (11 mo ago)

It wasn't quite what we discussed, but the mood just took me in this direction today. Well it's Sunday...
I broke the rule of doing 1 thing at a time...again  .
I checked and tightened all vacuum hoses to try and eliminate any possible vacuum leak. All seemed good.
I had a look at my pump nozzle which was a 31 so I happened to have a 37 old block style pump nozzle on an old carb so I tried that. I noticed that my orange coloured pump cam was in position 2 so I moved it to position 1 as I understand that will deliver more fuel too....
When I stomp my foot on the accelerator, I still have a huge (almost feels like it's going to die) hesitation but I think it did feel a little better and seemed more powerful to me.
My 02 gauge still suggests I have a massive lean moment when WOT.
I see my spare carb has a green pump cam... Does anyone know which colours deliver more fuel?


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## RMTZ67 (Mar 12, 2011)

fineline said:


> That's one sentence I'd never thought I'd hear.
> The car came that way. I have to admit I do like the sound. It's a real safety feature, as you can be heard in about a 3 mile radius.
> Just checked out those links. That sounds healthy. I'm hoping to hear just that, some time soon...


Also means the wifey/girlfriend can hear you coming, hope that's a good thing lol. I like to slip in unannounced.😆


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## Baaad65 (Aug 29, 2019)

There are pump cam charts all over the internet but they do vary I found, I can't remember if you have a vac secondary or mechanical but you need to isolate the bog to either the primary's or secondarys, you said when you stomp on it so is that putting it to the floor? How is it just stabbing the throttle quick up to the secondarys opening? And you're right changing more than one thing at a time leads to chasing your tail. First thing, is your timing all straight where it supposed to be? My hesitation was in the mechanical secondarys so I ended up with # 35 tube nozzles all around and a blue cam in the # 1 position, # 1 hole. Vacuum secondary adjustments are with the colored springs but I think they need to be checked under load. There are some good sites on tuning Holleys out there, just be careful on blogs because you'll get a hundred different solutions...except this one 😉


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## Baaad65 (Aug 29, 2019)

I should have posted this first, I'm just going on my experience and from help here plus Holley books and tech articles and the FOB site also emailed with the owner of the site. In no way am I an expert, plenty more smart people here but in my opinion you first take care of the timing like mentioned then any other things like vacuum leaks and such that have been mentioned then focus on the carb. You have do a process of elimination of all the things that can give you the hesitation. First I would make sure everything on the carb is in perfect working order(you can't adjust a faulty carb) so take it off and apart. Is the pump diaphragm good, are the floats good, needle and seats, blow out all the orifices, nothing binding, take notes of jet and power valve sizes. Next after all this is good to go properly adjust things, transfer slot, accelerator pump, throttle linkages. Now you can start tuning with idle mixture, cams, pump nozzles, jets, power valves, and only one thing at a time! Also keep checking vacuum inches, listen to your afr gauge, recheck timing, clean the plugs before adjusting the carb and watch them they tell a story, I was amazed at what can be told from the plugs according to the FOB site. Good luck and maybe some of this helps, I went through the same thing this summer and it's frustrating.


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## Lemans guy (Oct 14, 2014)

Fine..In post #7 you said it was a bog from a stop and that accelerating from say 40 to 50 MPH was ok. Has that changed?

Bogs from a stop are often a transfer slot improperly set, open to much at idle, so therefore it does not work and does not cover the “transfer” or transition from stop to go. You also said the idle adjustment screws did not work, another symptom of a transfer slot improperly set.

It can be many things and accelerator pump and cam as well. However if what you said still holds it is possible that your lean bog is from the transfer slot..


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## fineline (11 mo ago)

RMTZ67 said:


> Also means the wifey/girlfriend can hear you coming, hope that's a good thing lol. I like to slip in unannounced.😆


Ha! I may as well arrive with a marching band, It's that discrete. The windows of the house rattle when it's idling.
Luckily she shares my passion for the car...It must be true love...


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## fineline (11 mo ago)

Thanks for that Baaad65! I think I'm happy with the ignition timing now. It's at 10 or 12% initial and 36% total. If I get the chance I'm going to remove the carb today and go through the checks you mentioned.
After some internet search it does seem there is conflicting info on cam colours. Some suggested the green cam is the most aggressive so I gave it a shot (no pun intended). The cam shape was more aggressive looking for sure. I had to re-adjust my pump lever clearance to compensate for the new pump cam.
Still a big hesitation but it felt a little better still. I guess I've gone as far down that path as I can now.
Maybe my (massive) fuel filter is getting dirty (unlikely as I have a return line and that seemed to be flowing fine) or there was a slight carb blockage, as the AFR gauge was telling me I was running pretty lean the last run. In fact it was going up and down the gauge quite a lot but generally staying in the leaner area. It's done this before and just adds to my confusion.
I'm with you on the plugs, I'll recheck them today. I do clean them a lot for that reason.


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## fineline (11 mo ago)

Lemans guy said:


> Fine..In post #7 you said it was a bog from a stop and that accelerating from say 40 to 50 MPH was ok. Has that changed?
> 
> Bogs from a stop are often a transfer slot improperly set, open to much at idle, so therefore it does not work and does not cover the “transfer” or transition from stop to go. You also said the idle adjustment screws did not work, another symptom of a transfer slot improperly set.
> 
> It can be many things and accelerator pump and cam as well. However if what you said still holds it is possible that your lean bog is from the transfer slot..


It's still a bog from stop or slow speed. 40 or 50mph and it's ok.
That's a good point on the transfer slot. As I'm going to pull the carb off today I'll check that for sure thanks!
I rechecked and my idle speed screw was maxed out and still idling at 1100rpm.
With the vacuum advance connected that goes to over 2000rpm.


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## Baaad65 (Aug 29, 2019)

Something doesn't sound right with that idle maybe the problem has something to do with it. Is the carb new, has it been worked on by someone else?? The cams and nozzles are tricky as you can have a short time of spray with a lot of gas or less gas and longer time of spray, same with the nozzles.


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## fineline (11 mo ago)

Baaad65 said:


> Something doesn't sound right with that idle maybe the problem has something to do with it. Is the carb new, has it been worked on by someone else?? The cams and nozzles are tricky as you can have a short time of spray with a lot of gas or less gas and longer time of spray, same with the nozzles.


I agree I think something's not right with the carb. Though it was brand new when I fitted it, so it hasn't been messed with. Well other than the messing I just did. with pump cams and nozzles.
I replaced the old Holley carb because it was squirting a ton of fuel out of the breather and I couldn't stop it even after replacing the float valve.. Plus I felt it was a bit small for the engine..

I pulled the carb off and had a look at the transfer slot. After a bit of cleaning, It shows what I feel is more slot than should be showing. The info I found suggests that only a square should be showing below the butterflies. I have more than that showing. In fact the picture makes it look slightly less than it is showing.


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## Baaad65 (Aug 29, 2019)

It does look a little long but again I'm not an expert, is it just the picture or are the butterflies blackened especially the secondary. And do you have another carb you know is good you can throw on to compare? Don't forget to scrape all that gasket material off the base plate, it could cause a problem. Although new I've seen new stuff with problems like junk stuck somewhere from manufacturing, might want to take it all apart and check and clean everything.


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## fineline (11 mo ago)

It was very blackened, the picture was taken after some cleaning as it was hard to see the slots.
Unfortunately I don't have a known good carb to test with.
You can see the idle speed screw on the right of the picture has a large gap before making contact. I pressed the fast idle cam thingy, and it allowed the idle speed screw to contact the arm/lever. I guess this is when the choke opens?...I hope?  Then you can't see the slots at all.  
I'm not sure what position the fast idle cam should be in when I set the slot amount... I've been watching a ton of carb videos and am still confused. Wow carbs really are a dark art.


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## Lemans guy (Oct 14, 2014)

The fast idle cam screw should not be touching when you square the slot.

the carb lives in two worlds, cold and hot, ……so for general runningnmake all settings with engine at operating temp. Setting the transfer slot square with the carb upside down it does not need to be hot. Just make sure the fast idle screw is not touching.


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## fineline (11 mo ago)

Lemans guy said:


> The fast idle cam screw should not be touching when you square the slot.
> 
> the carb lives in two worlds, cold and hot, ……so for general runningnmake all settings with engine at operating temp. Setting the transfer slot square with the carb upside down it does not need to be hot. Just make sure the fast idle screw is not touching.


Just double checking, do you mean the fast idle cam screw? or the idle speed screw?


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## Lemans guy (Oct 14, 2014)

When you set the square transfer slot you do it with the throttle screw. When the engine is hot the fast idle cam screw should not be touching the fast idle cam. It is for cold operation only.

when you set the square for the transfer slot it is for normal hot operating temperature. But since it is off the car. You make that setting cold. If the fast idle screw is holding the throttle screw open it will not be correct.

for cold operation, you adjust choke and fast idle screw. When engine is cold.


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## fineline (11 mo ago)

Ah ok thanks! Well that's interesting! As when the choke is open and the fast idle is off, there is no slot showing at all. So I had to screw in/increase the idle speed screw to square off the slot. Yet my idle was already to high... . Could the carb have been pulling fuel from somewhere else at idle?, as it certainly wasn't pulling anything from the slot. I assume I may have a very high idle now?


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## Lemans guy (Oct 14, 2014)

A leaky power valve would could make your idle overly rich, floats too high, pressure too much. The power valve should only allow fuel to flow if the vacumn drops below the rating of the valve. A common valve is 6.5 Hg. So when vacumn is above that it does not allow fuel to pass through.

But if yours is old and defective it could be a couple it. It is an easy change. And Holley has videos on their web to walk you through it. Not expensive either. Get some bowl gaskets and a power valve and change it.


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## fineline (11 mo ago)

Funny you mention the power valve, I just removed it and noticed it has 2 gaskets (my fault)  . It was from a spare carb and it is a 6.5 . I tested it with a vacuum pump and it seems to work ok. It held vacuum, plus opened and closed.
Sadly I'm in France and everything is expensive here. a $5 part can easily turn in to a $50 part with customs taxes and shipping.
I rechecked the float height on the site plugs before removing the carb and all was good. My fuel pressure is 6psi 
Here's a shot down the intake manifold. Not exactly gasket matched.


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## Lemans guy (Oct 14, 2014)

Understand, yes it tests good keep it…..


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## fineline (11 mo ago)

I did find a badly fitted gasket on the secondary float bowl. It must have come from the factory like that.
Air can enter there. But I guess it probably won't make much difference as the car runs ok with the site plugs removed?  
Everything else in the carb checked out ok. 68 jets at the front and 75 at the back


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## Baaad65 (Aug 29, 2019)

And it wasn't leaking gas?


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## Lemans guy (Oct 14, 2014)

Those two gaskets on the power valve may have caused some fuel to pass thru there. Yes needs good gaskets there. Sounds like you need a vacation in Florida where you can then stock up on parts!


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## fineline (11 mo ago)

It wasn't leaking gas, but it was above the fuel level so it was ok...ish. I managed to manipulate the gasket back in to place for now. Got rid of one of the power valve gaskets. maybe that was letting some fuel past.
The carb is clean and back together. I managed to locate a used Edelbrock performer Intake at a reasonable price (reasonable for Europe  ) so I should get that next week.
I see that some people adjust their idle speed at the secondaries instead of the normal idle speed screw, using that little screw under the vacuum canister. I suppose that makes sense, as my squared off idle slot probably won't be squared off for long if I start adjusting idle from there?


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## fineline (11 mo ago)

Oh yes a parts buying trip to Florida would be great. The money saved on shipping and taxes would probably pay for itself.


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## Baaad65 (Aug 29, 2019)

fineline said:


> It wasn't leaking gas, but it was above the fuel level so it was ok...ish. I managed to manipulate the gasket back in to place for now. Got rid of one of the power valve gaskets. maybe that was letting some fuel past.
> The carb is clean and back together. I managed to locate a used Edelbrock performer Intake at a reasonable price (reasonable for Europe  ) so I should get that next week.
> I see that some people adjust their idle speed at the secondaries instead of the normal idle speed screw, using that little screw under the vacuum canister. I suppose that makes sense, as my squared off idle slot probably won't be squared off for long if I start adjusting idle from there?


It was suggested to me also to adjust the secondaries but mine is a double pumper and my bog was there in the secondaries, no bog up to that point. Have you looked up the site 4secondsflat.com it was really helpful with timing also.


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## fineline (11 mo ago)

I've not heard of that, I'll have a look, thanks..


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## fineline (11 mo ago)

Ok sorry for the delay. I'm back on this issue again and will get to the bottom of this, I hate it when threads don't reach a conclusion.
I was busy turning this.


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## fineline (11 mo ago)

In to this.
Sorry it's not strictly a GTO  but it's still a beauty. Completely ruined my manicure though.


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## fineline (11 mo ago)

Ok, I just checked the timing marks on the harmonic balancer (we are talking GTO now). And the timing tape looks to be for the wrong diameter harmonic balancer. (Previous owner job) . Assuming my calculations are correct. I measured the circumference of the harmonic balancer and divided it by 360 then x by what ever degree I was looking for. So if I need to set 36 degrees total timing.... on the tape I actually am at 49 degrees. oh that's not a small amount... The timing indicator on the engine looks to be ok though.
I can't wait to re set it and try it out....That's got to help.
It serves as a reminder to not trust anything done by a previous owner. When will I ever learn!...


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## Lemans guy (Oct 14, 2014)

Not unusual at all, your weights are likely giving you way too much ………


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## fineline (11 mo ago)

Weights? I'm not sure I understand.


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## Lemans guy (Oct 14, 2014)

Inside the distributor, under the cap and under the rotor, are two “weights” affixed by small springs. They operate by Centrifigal force based on RPM’s and spring tension. When you have 49 degrees of advance…the weights are likely adding in too much timing advance. Because of many reasons wear, wrong bushing or parts weak springs etc….

It is an easy fix and low cost. Then you can set base and Centrifigal timing correctly for generally around 36 degrees for best running.


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## fineline (11 mo ago)

Ah ok yes the distributor weights. I haven't opened the distributor up yet. I will do.
What I meant was the timing marks on my harmonic balancer were incorrect. Someone had installed a Summit degree tape for the wrong diameter balancer.
So when I tried to set my total timing to 36 degrees using the timing marks on the balancer, I was actually setting it to about 25 degrees BTDC as the marks were wrong. 
I made my own timing marks on the balancer and set it to a true 36 degrees total. Which according to the incorrect Summit tape came out at 49 degrees.
It sounds healthier in my opinion.... though when I plug the vacuum advance back in, it advances waaay too much when I throttle it. So I unplugged it again. 
Next stop is to pull the distributor and see what's up there.


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## Baaad65 (Aug 29, 2019)

fineline said:


> Ah ok yes the distributor weights. I haven't opened the distributor up yet. I will do.
> What I meant was the timing marks on my harmonic balancer were incorrect. Someone had installed a Summit degree tape for the wrong diameter balancer.
> So when I tried to set my total timing to 36 degrees using the timing marks on the balancer, I was actually setting it to about 25 degrees BTDC as the marks were wrong.
> I made my own timing marks on the balancer and set it to a true 36 degrees total. Which according to the incorrect Summit tape came out at 49 degrees.
> ...


Probably have to try a different vac advance module, there's a Lars adjustable one or a limiter because you should only have 10-12 degrees of advance on the vac can.


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## fineline (11 mo ago)

Baaad65 said:


> Probably have to try a different vac advance module, there's a Lars adjustable one or a limiter because you should only have 10-12 degrees of advance on the vac can.


I've not heard of that brand before. I did a little searching but came up empty handed, do you have a link to one of those? Or know where the best place to look is? Thanks.


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## Sick467 (Oct 29, 2019)

This is a good primer for Lars Grimsrud...



http://corvette-restoration.com/wp-content/uploads/technical_papers/Vac_Adv_Spec.pdf



It's not so much a brand, but a "who".


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## fineline (11 mo ago)

Ah ok, thanks, I'll have a look through that.


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## fineline (11 mo ago)

I noticed the last time I switched off the engine, there was a hissing sound coming from somewhere.(I can never tell where from with all the noises). As I've checked everywhere I can think of except the brake booster itself, I put my vacuum pump on it, and I cannot get any vacuum. Ahaa. This could be it! 
Trouble is it could be anything up to a month to get a new one shipped here to Mars...er France I mean.


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## Lemans guy (Oct 14, 2014)

Just verifying that you are not seeing 36 degrees at “idle” that should not be until about 3000 RPM’s….your idle timing should be much lower. 36 is for total timing


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## fineline (11 mo ago)

Thanks. It was about 12 degrees at idle and 36 degrees tops. not sure what the revs were but it was high enough for sure.


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## fineline (11 mo ago)

Apologies for the epic delay. Life does get in the way sometimes. 
The new brake booster is on and I've finally got round to testing it.....Well I have brakes now which is nice, but alas the hesitation still exists. I notice on my 02 gauge that I'm running even richer at idle. It was running rich before, which probably explains why I didn't have any starting issues even with the vacuum leak. My idle mixture screws are only about 1/2 to 3/4 of a turn out, which I know isn't very good. I lowered the float level a tad more but that didn't help much.
I'm not sure how to lean the carb out any further?


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## Scott06 (May 6, 2020)

fineline said:


> Apologies for the epic delay. Life does get in the way sometimes.
> The new brake booster is on and I've finally got round to testing it.....Well I have brakes now which is nice, but alas the hesitation still exists. I notice on my 02 gauge that I'm running even richer at idle. It was running rich before, which probably explains why I didn't have any starting issues even with the vacuum leak. My idle mixture screws are only about 1/2 to 3/4 of a turn out, which I know isn't very good. I lowered the float level a tad more but that didn't help much.
> I'm not sure how to lean the carb out any further?


Long thread apologies if you already checked - have you verified fuel pressure is ok I replaced my fuel pump and found my fuel bowls were over flowing on new pump had to put a regulator in. I noticed on my air fuel ratio gauge that the AFR was going real rich at times 11 or so then come back up. Saw fuel bowls (tripower) intermittently dumping gas down carbs. Set it to 3.5-4 psi eliminated the issue.


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## fineline (11 mo ago)

I think the pressure is ok. With the sight plugs out and the fuel pump on, no fuel spills out unless you rock the car. It's set at 6psi.
Maybe I'll just have to live with the hesitation. Besides I've got an even more serious problem that really needs sorting...wheel hop.


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## geeteeohguy (Feb 2, 2008)

fineline said:


> I think the pressure is ok. With the sight plugs out and the fuel pump on, no fuel spills out unless you rock the car. It's set at 6psi.
> Maybe I'll just have to live with the hesitation. Besides I've got an even more serious problem that really needs sorting...wheel hop.


If that's your car in your avatar, I can see why you have wheel hop!


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## fineline (11 mo ago)

It is indeed my car.


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## PontiacJim (Dec 29, 2012)

fineline said:


> I think the pressure is ok. With the sight plugs out and the fuel pump on, no fuel spills out unless you rock the car. It's set at 6psi.
> Maybe I'll just have to live with the hesitation. Besides I've got an even more serious problem that really needs sorting...wheel hop.


Wheel hop becomes a bigger problem when you raise the rear of the car. You have changed the pinion angle and changed the angles of the upper/lower control arms. Worn control arms bushings can also add to the problem.

To correct, you may want to get new control arm bushings and use "no hop bars" which bolt up to the rear end and raise the upper contol arms higher to get the geometry back - they are basically hidden from view. You would also want to get adjustable upper control arms to fine tune your pinion angle. With this, I would suggest the upper/lower control arm frame braces (many aftermarket styles to include factory repro's), and a good quality set of shock - adjustable settings would be prefered.

Option 2 might be coil style "slapper bars", or traction bars. These can reduce road clearance and are visibly seen. Still would suggest the adjustable upper control arms to fine tune your pinion angle. With this, I would suggest the upper/lower control arm frame braces (many aftermarket styles to include factory repro's), and a good quality set of shock - adjustable settings would be prefered.

Don't let the wheel hop get excessive as you may break the rear end, wear out the u-joints, or even break the end of the transmission.


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## fineline (11 mo ago)

Thanks Jim! 
Those are the springs that came with the car when I bought it. I wasn't sure if they were standard size or not as the 14" wheels probably make it look worse than it is.
In fact those springs are the only thing I haven't replaced. I bought Del-sphere adjustable upper and lower control arms in the hope that I could eliminate the hop. I bought an angle finder to adjust my pinion angle but no luck so far. Assuming I've done it right. I think I did.
New shocks didn't help either.
I made a pair of frame braces, you can see a gold-ish silver ish bar above the muffler on one of the picks.


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## PontiacJim (Dec 29, 2012)

fineline said:


> Thanks Jim!
> Those are the springs that came with the car when I bought it. I wasn't sure if they were standard size or not as the 14" wheels probably make it look worse than it is.
> In fact those springs are the only thing I haven't replaced. I bought Del-sphere adjustable upper and lower control arms in the hope that I could eliminate the hop. I bought an angle finder to adjust my pinion angle but no luck so far. Assuming I've done it right. I think I did.
> New shocks didn't help either.
> I made a pair of frame braces, you can see a gold-ish silver ish bar above the muffler on one of the picks.



OK, then you may need the "no hop" bars to raise the rear of the upper control arms - or install new factory height rear springs and tires that will fit, but then you loose the look. Some guys used to install the Lakewood ladder bars (they looked cool) which really helped, but not good on the street because they don't allow the rear end to flex - like going into curves. My brother used a set on his '67 GTO and they did the trick - but it also put too much strain on his frame and cracked it and he had the cracks welded up and removed the ladder bars.

I have never used the "no hop bars," but have always been aware of them and their purpose to correct the 4-control arm geometry used in the A-bodies. BUT, the old bias tires were also different and generally you could smoke the tires getting them spinning so not too often you had wheel hop. Going to wider tires that gripped more road and a posi would then lead to wheel hop.

Had bad wheel hop on a '65 Impala with its stock 10-bolt and the cure was to learn how to take off from a stop without full power causing wheel hop. Lower RPM and a little clutch slip to just get the car rolling to take up the shock and then flat floor the gas pedal and take off. Then I fitted a larger 12-bolt 9.3 rear end from an Oldsmobile (was told it was a Chevy and I learned different) and had to make my own adapted upper control arms. I went straight up with a section of control arm to where my other forward section came off the crossmember and the 2 pieces intersected like a 90 degree angle - sorta like a poor boys "no hop bar". Then I welded (with gas torches and coat hanger) the 2 pieces together. Made a huge difference in traction. Wheel hop was basically gone and I could simply smoke tires at will. Then I learned how to take off without overpowering the tires and smoking up the M-50's and pull away like a freight train. So that proved to me that the purpose of the store bought "no hop bars" worked, except I had home built that cost me nothing but some time to fabricate. Made my own "no hop bars" for my '68 Lemans - maybe they will work, or maybe not.


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## fineline (11 mo ago)

Thanks for all that info Jim! Ok I might give the ladder bars a miss then as a cracked chassis doesn't sound too good.
As shipping and taxes have gone insane in the last year or so, I did start to make a pair of no hop bars, maybe I'll try and get them finished then. I can't remember why I stopped.
I've had the wheel hop ever since I converted it from automatic to manual. So it's my fault really, I do regret doing that. Plus it was nightmare to do. But I just prefer manual.
I've had these old tires and 14" wheels on this thing since I bought it. I was hoping to smoke them to death and get rid of them. But the wheel hop just gets in the way.


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## PontiacJim (Dec 29, 2012)

fineline said:


> Thanks for all that info Jim! Ok I might give the ladder bars a miss then as a cracked chassis doesn't sound too good.
> As shipping and taxes have gone insane in the last year or so, I did start to make a pair of no hop bars, maybe I'll try and get them finished then. I can't remember why I stopped.
> I've had the wheel hop ever since I converted it from automatic to manual. So it's my fault really, I do regret doing that. Plus it was nightmare to do. But I just prefer manual.
> I've had these old tires and 14" wheels on this thing since I bought it. I was hoping to smoke them to death and get rid of them. But the wheel hop just gets in the way.


Yes, the manual trans will cause more of an issue because you are "shocking" the rear axle when you dump the clutch - with an automatic, you don't rev the engine and drop it into drive, you use the converter so a much softer hit on the driveline in general.

Here is an example of the no-hop bars which I fabricated for my car - but I have a Ford 9" and a bunch of suspension/frame upgrades and they had to be fabricated for my application. Also have the spacers under the rear springs to lift the rear of the car up, so the angle on the top control arms were so steep that I had no travel of the stock arms. Upper control arms are also fabricated, but the goal was to get the uppers about at the 90 degree angle at the back of the upper and the attachment point on the no-hops. Extra holes were drilled so I can adjust them to find the best position when testing them. I also drilled new holes in the lower control arm mounts to move the tubular lowers up a little higher to compensate a little for the extra lift and reduce their angle. Again, just winging it here based on what I believe will work, but no hard evidence until the car hits the road - which is a few years off.


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## fineline (11 mo ago)

That looks like a lot of work!. That's an interesting way of mounting the no hop bars to the axle. Maybe that's because of having a Ford 9" ? It seems more straight forward than the QA1 type design.
Come to think of it, maybe my adjustable upper control arms won't fit with the commercially available design of no hop bars...


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## fineline (11 mo ago)

Also do you think "rear lower control arm relocation brackets" might help?


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## PontiacJim (Dec 29, 2012)

fineline said:


> Also do you think "rear lower control arm relocation brackets" might help?



No. You don't want to mix no-hop bars with the lower relocation brackets. The no-hop bars are the better choice. 

Here is a picture of the Dick Miller no-hop bars and adjustable upper control arms for a 12-bolt for reference. He also has these for 10-bolt. You can see the style of adjustable UCA's that is used with the no-hop bars. 2-holes in the no-hop bars for fine tuning.


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## fineline (11 mo ago)

That's a shame, it looks like I'd need the no hop bars and another set of UCA s. Maybe I'll have to design my own versions to work with my UCAs.
Thanks!


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## armyadarkness (Dec 7, 2020)

fineline said:


> That's a shame, it looks like I'd need the no hop bars and another set of UCA s. Maybe I'll have to design my own versions to work with my UCAs.
> Thanks!











FAQ - Chassis/Suspension/Steering: GTO SUSPENSION...


GM A Bodies/ Pontiac GTO's have a ton of room for improvement in their suspensions. Putting aside personal preferences for ride height and quality, if you want a car that: Handles better Brakes better Steers better Has no wheel hop Has increased traction Recovers quickly from burnouts and loss...




www.gtoforum.com


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## fineline (11 mo ago)

Thanks! My heart sank a little further when I read "*Can have spherical on the rear upper and lower arms but only on one end of the arm! Consider spherical for the frame side of the lower and the diff side of the upper." * I think that's the opposite for my UCAs . I'm not sure why that is? Plus I think my lowers are spherical on both ends too...Maybe I'll have to start all over again or go back to stock.


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## armyadarkness (Dec 7, 2020)

fineline said:


> Thanks! My heart sank a little further when I read "*Can have spherical on the rear upper and lower arms but only on one end of the arm! Consider spherical for the frame side of the lower and the diff side of the upper." * I think that's the opposite for my UCAs . I'm not sure why that is? Plus I think my lowers are spherical on both ends too...Maybe I'll have to start all over again or go back to stock.


Im not sure that's a deal breaker, although possibly not optimal. If you had spherical at the diff side of the lowers, I'd be more alarmed. A few of the others might have more to say on it.


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## armyadarkness (Dec 7, 2020)

Not having spherical on both ends is what's very critical.


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## ponchonlefty (8 mo ago)

PontiacJim said:


> Yes, the manual trans will cause more of an issue because you are "shocking" the rear axle when you dump the clutch - with an automatic, you don't rev the engine and drop it into drive, you use the converter so a much softer hit on the driveline in general.
> 
> Here is an example of the no-hop bars which I fabricated for my car - but I have a Ford 9" and a bunch of suspension/frame upgrades and they had to be fabricated for my application. Also have the spacers under the rear springs to lift the rear of the car up, so the angle on the top control arms were so steep that I had no travel of the stock arms. Upper control arms are also fabricated, but the goal was to get the uppers about at the 90 degree angle at the back of the upper and the attachment point on the no-hops. Extra holes were drilled so I can adjust them to find the best position when testing them. I also drilled new holes in the lower control arm mounts to move the tubular lowers up a little higher to compensate a little for the extra lift and reduce their angle. Again, just winging it here based on what I believe will work, but no hard evidence until the car hits the road - which is a few years off.
> 
> ...


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## PontiacJim (Dec 29, 2012)

Yes, going mid-to-late 1970's look when all said and done.


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## fineline (11 mo ago)

Sadly I do have spherical on the diff side of the lowers... but not on the diff side of the uppers, which sounds like the opposite of what I need....possibly?.


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## fineline (11 mo ago)

Actually I have spherical joints on both ends of the uppers and lowers. No idea what that means?


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## armyadarkness (Dec 7, 2020)

fineline said:


> Actually I have spherical joints on both ends of the uppers and lowers. No idea what that means?


Spherical or "roto" joint provide the ultimate articulation, but since the control arms play the primary role in alignment, they're solely responsible for planting the differential housing where the factory intended, and relevant to the rest of the driveline.

If all of your joints have 100% articulation, then what's keeping the rear in line?

The idea of improved articulation in the joints, is to decrease bind and increase traction by maximizing the contact patch... but there's also such a thing as overdoing it. 

You want the rear tires to float up and down, independently and in unison, with as little bind as possible. But if all of the joints are roto, then the diff can potentially move from side to side as well.


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## fineline (11 mo ago)

I guess the 4 link mounting points with differing angles between upper and lower would keep it in line....I think? The spherical joints do have 100% articulation but don't seem to have any side to side play.  It's hard to get my head around, if the springs were taken out and the car jacked up, would there be any side to side axle play?
I might try it...


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## RMTZ67 (Mar 12, 2011)

Damn...you guy's sound like a couple of doctors, talking about my body. Dr Army & Dr Fineline to the emergency....STAT.


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## fineline (11 mo ago)

Unfortunately Dr Fineline is highly under qualified. But does have his sights set on a good firm rear end.


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