# Gas smell or running rich



## Cmeyer9424 (May 5, 2020)

Hey guys, read a few post and didn’t see any that fit what I’m encountering. When I start the car and let it idle you can smell gas fumes. Not like straight gas but like possibly running rich. I pulled it out of the drive turned around and backed it up into the carport and my shirt now has a slight smell of exhaust and or gas to it. It was probably 5min max of being around the car. Also, a buddy was over today and said it smelled rich. I don’t have the extra $$ right now for the AFR ratio gauge to see what it is exactly doing for that aspect. 

I posted previously about a stumble with the carb where it was running lean and adjusted the 750 Holley double pumper to have a 50cc primary and 35 nozzle in both. I went larger and it didn’t like that so this is where I ended up. 

Gotta get this figured out, the wife wont ride in it like this haha!

Open to any suggestions, thanks!


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## Lemans guy (Oct 14, 2014)

The accelerator pump does not effect idle unless it is leaking internally. Your idle circuit may just need a slight adjustment you didn’t say what carb you have but they all have idle mixture adjustments...

generally turning the screw clockwise will lessen and therefore lean the idle mixture and turning CC will open and therefore richer the mixture.....

you can go back to your carb’s original idle setting procedure......

make sure floats are set to proper spec height first and you have to adjust the mixture and the throttle screw together to get it just right,...use small changes and test....

try one eight of a turn in on the mixture screws and the drive it,...even that change will show up on an AFR meter...


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## Lemans guy (Oct 14, 2014)

Sorry I missed it was a Holley double pumper.....yes adjust the mixture screws....


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## Cmeyer9424 (May 5, 2020)

I’ll try that tomorrow! I adjusted the floats when I had that carb apart. Did it where you flip them over and adjust them in line with the screws. I think I’m explain that correctly ha.


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## GTO44 (Apr 11, 2016)

Plug a vacuum gauge into manifold vacuum. Adjust the idle air/fuel mixture screws for max vacuum.

If ur having trouble with a starting point... screw all the air/fuel mixture screws all the way in and back about a turn and a half. Start there and make 1/4 turn adjustments at a time (both sides at the same time for each adjustment) while watching the vacuum gauge. Keep adjusting until the vacuum gauge levels off the highest vaccum. 

As lemans guy said tightening the screw (screwing it in) will lean the mixture while loosening the screw (screwing it out) will richen the mixture.

As stated make sure your float levels are correct first. Take the sight plug out of the float bowl with the car off. You should be able to rock the car and have some fuel come out of the hole. If you take the sight screw out and fuel pours out you need to lower the float level. Do this with the primary and secondary float bowl. Remember, After an adjustment to the float you need to put the sight screw back in, start the car and run for a couple seconds. Then shut it down and check the the float level again to see the results.


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## Cmeyer9424 (May 5, 2020)

I’ll give an update in the morning once I do these adjustments. Thanks!


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## PontiacJim (Dec 29, 2012)

Keep in mind a camshaft with a lot of overlap can give you that raw gas smell out the exhaust because its blowing unburned fuel out the exhaust.


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## Lemans guy (Oct 14, 2014)

I know you were changing your accelerator pump nozzles and pump. One thing that will drive you crazy with hard cold rich starts is a leaking accelerator pump check valve.

in the newer versions it is a small rubber umbrella looking valve, older ones had a ball bearing style....Have you changed that umbrella valve? They do go bad and don’t seal...

when that happens you get a hard cold start, and it is frustrating. Holley sells them on their web, or any vendor that sells Holley carb parts. If you take off the accelerator pump check it if it looks warped like it is not flat it is not sealing.

that will make you rich at idle also.........


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## Cmeyer9424 (May 5, 2020)

I haven’t changed that but I remember seeing it when I was changing the parts. The car does sit for a few days and fires up fine but then will die with out a little throttle at first. After that it starts and idles fine. 

I started it yesterday and being the coldest day since Ive owned it, about 60 outside, it really didn’t wanna stay running. Had to work the gas for a minute or so. Would the check valve be related to this or the fact that it is a manual choke version with the choke just wide open since the manual choke linkage isn’t setup?


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## Cmeyer9424 (May 5, 2020)

Also, I remember seeing a video from Holley on setting the mixture screws and they said to have it in drive while making the adjustments. Is this required or can you do it well enough in park? No big deal either way, just need to know so I can call a friend haha


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## Lemans guy (Oct 14, 2014)

You need to have the choke properly adjusted for cold starts, it may not be closed enough during that initial 60 seconds which makes it richer.....your hitting the pedal squirts gas in and riches it, might need a slight more choke...

no set the idle in park or neutral, with wheels chocked and brake on.

First see what the RPM is at idle in drive, and at idle in park or neutral..

park or neutral will be higher, note the diference......

say it is 700 RPM in drive and 900 Rpm in park.......maybe you want 600 in drive.....

then drop that 900 Rpm to 800 Rpm.....then put it in drive is is 600? ....

adjust that way and you can dial it in much safer, and alone.....


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## Cmeyer9424 (May 5, 2020)

I’m gonna order a choke cable to help out with the cold starts. Unfortunately I don’t have a tach gauge yet either


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## Old Man Taylor (May 9, 2011)

What vacuum do you see at idle, and what are the values of your power valves?


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## GTO44 (Apr 11, 2016)

Cmeyer9424 said:


> Also, I remember seeing a video from Holley on setting the mixture screws and they said to have it in drive while making the adjustments. Is this required or can you do it well enough in park? No big deal either way, just need to know so I can call a friend haha


You dont do it while you drive. But you want to do it when the car is fully warmed up. Thats why they probably mention driving it. The mixture screws are your idle circuit and dont effect the primary, secondary or accelerator circuits.


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## Ebartone (Aug 18, 2019)

Cmeyer9424 said:


> Hey guys, read a few post and didn’t see any that fit what I’m encountering. When I start the car and let it idle you can smell gas fumes. Not like straight gas but like possibly running rich. I pulled it out of the drive turned around and backed it up into the carport and my shirt now has a slight smell of exhaust and or gas to it. It was probably 5min max of being around the car. Also, a buddy was over today and said it smelled rich. I don’t have the extra $$ right now for the AFR ratio gauge to see what it is exactly doing for that aspect.
> 
> I posted previously about a stumble with the carb where it was running lean and adjusted the 750 Holley double pumper to have a 50cc primary and 35 nozzle in both. I went larger and it didn’t like that so this is where I ended up.
> 
> ...


Another idea might be to check your choke pull off. If the pull off is not pulling off enough, the choke flap will cause a very rich mixture. I had this problem once, and the exhaust was a very white color and I could smell a great deal of gas Until it warmed up and went off choke. With the Quadra jet it was simply bending a tang, and I got it back to the right opening and solved the problem. Just a thought.


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## Cmeyer9424 (May 5, 2020)

So I finally got the manual choke installed and helps a lot from a cold start but standing at the back of the car the exhaust smell is very strong. Kinda makes your eyes water ha. Not sure if that’s just how it is due to the cam installed in it


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## Cmeyer9424 (May 5, 2020)

This afternoon I adjusted the float levels and the air/fuel screws to where the max manifold vac seen was 11 at idle.


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## PontiacJim (Dec 29, 2012)

Cmeyer9424 said:


> This afternoon I adjusted the float levels and the air/fuel screws to where the max manifold vac seen was 11 at idle.


Just for comparison, a stock Pontiac will have 18-22 inches of vacuum. So, you definitely have a cam with some overlap. Overlap is when the intake valve and exhaust valve are open at the same time, so some fresh gas is pushed out the exhaust at idle/lower RPM's - not at higher RPM's when the power begins to turn on.

That said, what you are experiencing may be perfectly normal based on the cam's overlap. I have experienced this and been around other built up engines that would also emit a gas smell and burn your eyes.

Not sure if you play around with your timing and timing curve, raise the idle a bit, and/or re-adjust the carb settings again. You could play around more, but if it is running good and strong with no other issues, then I'd just go with it - it may be the nature of the beast.


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## Cmeyer9424 (May 5, 2020)

Thanks for the info! When I check the vacuum, do I need to plug the line leading to the distributor advance or can I just leave it hooked up?
I also noticed that the driver side exhaust pipe is cut off just over the axel and is angled sorta towards the trunk. Wonder if this is pushing exhaust up into the trunk area and then coming into the cab? Just thinking out loud.


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## Old Man Taylor (May 9, 2011)

You can leave the vacuum line to the distributor open as long as it is blocked to the vacuum source.

The tail pipe isn't right, but it shouldn't be making a difference outside the car.


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## Cmeyer9424 (May 5, 2020)

It doesn’t bother me really outside the car it’s just bad when I’m cruising around and the exhaust gets to my eyes.


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## Old Man Taylor (May 9, 2011)

Fix that tail pipe and it should get better.


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## Cmeyer9424 (May 5, 2020)

Got the tail pipes reworked and installed some turn downs and it 80% better! Something strange did happen ever since I adjusted the float level and the air/fuel screws, my bog at is back when I put it to the floor. Not sure how that would have effected that issue since it was doing fine before


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## Lemans guy (Oct 14, 2014)

First I would make sure the pump cam adjustment is correct, tight up against the accelerator pump arms, a gap will delay the fuel shot and give you a lean bog.

mixture screws never actually turn off providing some duel, at idle and below 2500 RPM or so they act alone, but after that primaries and secondaries and power valves come into play, but the mixture screws are still working albeit a smaller percent of the mixture.

So say that you leaned out the mixture screws and dropped the float level, that slight change could cause a leaner overall mixture and a lean bog. The fix would be to then up the secondary jets. To compensate for theadjustment. This is fine tuning for sure. But a bog at speed tends to be mostly a lean bog, and often is the accelerator pump lagging because the gap or cam is wrong, or the pump squirter is inadequate.

you can also have a rich bog, but they are usually lean. It happens because the carb gulps air when you push the pedal down and the fuel has not caught up, the accelerator pump shot is supposed to cover that.


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## Cmeyer9424 (May 5, 2020)

It definitely seems to be a lean bog, pretty bad too. I will check adjustments on the arm. I also have a 50cc pump for the secondary if I need to install it.


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## Lemans guy (Oct 14, 2014)

Yes, sounds like you need more of a fuel shot to cover that lean bog,....check and adjust gap on accelerator pump arm first, then you might need that 50cc squirter.

if funds allow some of the best things you can do is to run wide band oxygen gauges, one or two and a vacumn gauge in the cab. You can see what all these changes are doing to your AFR and can really dial it in exactly......

you can watch your vac gauge and when vac dips below whatever power valve you are running you can see the change to rich, or watch when accelerator pump comes on or tell if your secondaries are too lean or too rich......as it happens...

you can re jet or adjust mixture or change power valves etc as necessary."


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## Cmeyer9424 (May 5, 2020)

Checked the pump arms and they are good. Also checked all the plugs, the were good as well. To it for a drive and still have the lean bog and even had a backfire through the carb. Also, what does it mean when you put it in reverse and it dies if you don’t slightly burp the throttle? Idle seems good in park and once it stays running it’s good as well in drive or reverse


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## Lemans guy (Oct 14, 2014)

It seems like all signs that you may be too lean......too lean can cause a backfire on deceleration as can too much timing advance.....the bog at speed is often lean,.....too rich can cause bog as well,.....so you have to get your mixture right...


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## Cmeyer9424 (May 5, 2020)

In the next day or so I’m gonna put the 50cc on the secondary and check it again.
What about it dying when put into gear if throttle is not given a bit?


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## Lemans guy (Oct 14, 2014)

If it’s cold in first couple of minutes it may be too lean as well. The choke will richer it for a minute minute and a half, let it idle in part at fast idle. Then you should be able to go to drive without a stall if the mixture is right and your idle is not set to low....

enrich it a bit on the mixture screws, and see if it improves a tad. 1/8 a turn on each counterclockwise will enriched


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## Cmeyer9424 (May 5, 2020)

Put the 50cc pump on and the throttle seems to be a tad more responsive but still having a bog. Also I upped the mixture screws and that fixed the dying when put into gear problem! I talked to a buddy of mine and he said to work the throttle with it in park to confirm that the big is caused by the carb rather than the vac advance not working properly. I have a video of it in park and you can hear it bog. I also have a video of the amount of fuel that is coming out as I work the throttle. He saw the videos and thought it was too much fuel.

On a side note, a total surprise to me the previous owner to the guy I bought the car from recognized the car from an Instagram post and reached out. He’s sending me a bunch of parts that originally came with the car! I picked the guys brain about the motor build and he said when he bought it the original owner had the 400 built by a professional engine shop in Arkansas. He then proceed to say it would lay rubber until he let out of it!! So I now know for a fact this car has some good power hiding in it I just have to find out what is holding it back.


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## Cmeyer9424 (May 5, 2020)

Here’s the video links, let me know if they work. 

In Park Bog

Carb Fuel Flow


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## PontiacJim (Dec 29, 2012)

Cmeyer9424 said:


> Here’s the video links, let me know if they work.
> 
> In Park Bog
> 
> Carb Fuel Flow


Not a Holley guy, but I would definitely say too much gas on the pump shot - which could be your bog problem for right now.

The 50cc pump is probably OK, just now your squirters are too big. Go back to small squirters. My thinking is the 50cc pump will give you a longer squirt/smaller stream using a smaller sized squirter - which is what you want, vs the 50cc pump dumping a lot of gas in a short time and causing the engine to load up and bog. So try and now balance the squirters to the 50cc pump's flow.


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## Cmeyer9424 (May 5, 2020)

I have a 31 and a 28 that originally came with the carb. It has 35 in both right now.


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## Old Man Taylor (May 9, 2011)

What power valve do you have in the carb, and what is the idle vacuum?


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## Cmeyer9424 (May 5, 2020)

Old Man Taylor said:


> What power valve do you have in the carb, and what is the idle vacuum?


The idle vac was around 11-12 last time I checked. I’m not sure for the power valve, never checked it before


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## Old Man Taylor (May 9, 2011)

The typical Holley power valve is 10.5. That would be too high for your idle vacuum. I would drop it to 8.5.


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## Cmeyer9424 (May 5, 2020)

Old Man Taylor said:


> The typical Holley power valve is 10.5. That would be too high for your idle vacuum. I would drop it to 8.5.


Should I change that and the nozzle size or do the power valve first. What nozzle would you recommend?


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## Old Man Taylor (May 9, 2011)

Cmeyer9424 said:


> Should I change that and the nozzle size or do the power valve first. What nozzle would you recommend?


I would start with the power valve first, as that may help or solve your problem. Every car is different, but I ran the 0.035" nozzles.


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## Old Man Taylor (May 9, 2011)

My guess is that you don't know how a power valve works. The number stamped on it (e.g., 10.5) is the vacuum level where the valve will start to open. There's a more complicated formula for calculating what is best, but with small cams the rule of thumb is 2 numbers lower than your idle vacuum. In your case that would be about 9.5, but they only come in even numbers, hence 8.5 for you. If I'm guessing right, then you're running too rich all the time as the power valve is opening too early.


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## Cmeyer9424 (May 5, 2020)

Old Man Taylor said:


> My guess is that you don't know how a power valve works. The number stamped on it (e.g., 10.5) is the vacuum level where the valve will start to open. There's a more complicated formula for calculating what is best, but with small cams the rule of thumb is 2 numbers lower than your idle vacuum. In your case that would be about 9.5, but they only come in even numbers, hence 8.5 for you. If I'm guessing right, then you're running too rich all the time as the power valve is opening too early.


I’ll get one ordered! Thanks for the info on how it works, you were correct I didn’t know haha!

I do believe it has a decent size came in from just the sound of it. I’ll attach a video of it. It has electric cutouts in the video
Idle with Cutouts


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## Cmeyer9424 (May 5, 2020)

Also, do I need one or two power valves since it a double pumper?


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## Lemans guy (Oct 14, 2014)

It could, but some just have a plug there. You need to take off the bowl and the next section of the card, the metering block and look. Also some Holley’s have 6.5 power valves, like Mr Taylor said some 10.5. I have idle vac at 12 and run an 8.5 power valve in. Y quick fuel carb, which is identical to a Holley but much more adjustable. Holley owns quick fuel.

Under you power valve are two fixed orifices,..called Power valve channel restrictions..PVCR....the valve opens at a set vacumn level, below that level it is open. They are very gradual, every one I test pretty much just opens below the level stamped on the valve. What really controls the Dow of fuel are the PVCR. Not really adjuable on a Holley, you can drill them bigger but Hyatt is ill advised.

however on a Quick Fuel they are screw in jets of various sizes and easily adjustable. I change them rich or lean to get the correct AFR.

saw your video, agree with Pj and OMT..squirter look rich. Get some smaller ones from Holley, try a 33 in that rear or 32...And lean it a bit. Also is that bog justin park? Does it do that at speed under load? You may be a bit rich but under load it needs more than in park.

an 8.5 power valve will help as now whenever you touch the gas the power valve is opening if it is a 10.5. I thinkyou might have a 6.5 power valve and when you hit it like in the video it comes on a bit later and dumps that fuel on top of the really rich squirter...so it bogs.....

a vacumn gauge and an AFR gauge working off a wide and 02 sensor would tell you exactly what the vacuum reading and the AFR reading is at the bog. Then you can diagnose it easier. I can watch my vac gauge and see when it hits 8.5, a glance at the AFR meter shows a drop to 12.2 AFR. Because I set the PVCR to get that. But not saying you must have that. But a vac gauge is an easy hookup to watch while driving and can really help with all sorts of drivability issues.

you will get it, you are fine tuning it now.....


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## Cmeyer9424 (May 5, 2020)

Lemans guy said:


> It could, but some just have a plug there. You need to take off the bowl and the next section of the card, the metering block and look. Also some Holley’s have 6.5 power valves, like Mr Taylor said some 10.5. I have idle vac at 12 and run an 8.5 power valve in. Y quick fuel carb, which is identical to a Holley but much more adjustable. Holley owns quick fuel.
> 
> Under you power valve are two fixed orifices,..called Power valve channel restrictions..PVCR....the valve opens at a set vacumn level, below that level it is open. They are very gradual, every one I test pretty much just opens below the level stamped on the valve. What really controls the Dow of fuel are the PVCR. Not really adjuable on a Holley, you can drill them bigger but Hyatt is ill advised.
> 
> ...


Yes the video is in park for the bog. I will take the carb apart tomorrow and update on what sizes in primary as well as secondary. I have a 31 nozzle I could put in the secondary and leave the 35 in the primary if that would possibly work. If not, I can order some.


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## Old Man Taylor (May 9, 2011)

I would bet that the power valve fixes the stumble at idle.


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## BearGFR (Aug 25, 2008)

Cmeyer9424 said:


> Also, do I need one or two power valves since it a double pumper?


Usually, Holleys only have power valves on the primary side, and a plug on the secondary, but you'll be able to tell when you take it apart.

Bear


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## Cmeyer9424 (May 5, 2020)

I took the carb apart this morning and it looked to be stamped 6.5 I took a picture as well to make sure. Also, the jetting size is 71-Primary 80-Secondary and the secondary did have a blocking plate for the power valve. The manifold vac at idle was 10.5-11


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## BearGFR (Aug 25, 2008)

Cmeyer9424 said:


> I took the carb apart this morning and it looked to be stamped 6.5 I took a picture as well to make sure. Also, the jetting size is 71-Primary 80-Secondary and the secondary did have a blocking plate for the power valve. The manifold vac at idle was 10.5-11


Here are some samples:


https://www.thirdgen.org/forums/attachments/carburetors/195013d1268598328-about-holley-tuning-sticky-powervalve01.gif




http://www.crankshaftcoalition.com/wiki/images/thumb/2/25/Holley_pv_stamping1_id.jpg/400px-Holley_pv_stamping1_id.jpg




http://i241.photobucket.com/albums/ff90/Fab_64/IMG_4018c.jpg


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## Cmeyer9424 (May 5, 2020)

Yes then it is a 6.5 power valve


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## Old Man Taylor (May 9, 2011)

You still need to change it to an 8.5.


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## Cmeyer9424 (May 5, 2020)

Old Man Taylor said:


> You still need to change it to an 8.5.


Got an 8.5 order. What is the difference in performance sense between the 6.5 and 8.5? I understand how they work now just curious since one will allow fuel sooner than the other. 

Also, I’ve been watching and reading a bunch on timing and I believe the 31 total leaves room for more, possibly up to 38 or so. I’m just hesitant because I know too much is far worse than too little. I haven’t been around enough older vehicles to know the sound of too much.


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## Old Man Taylor (May 9, 2011)

The lower the number the lower vacuum it takes to provide extra fuel. So until your engine vacuum drops that low, you don’t get the extra fuel.


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## Old Man Taylor (May 9, 2011)

I don’t know what heads or compression ratio you have. But, the engine should like 36 degrees with open chamber heads - as long as there’s no pinging or detonation.


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## Cmeyer9424 (May 5, 2020)

Old Man Taylor said:


> I don’t know what heads or compression ratio you have. But, the engine should like 36 degrees with open chamber heads - as long as there’s no pinging or detonation.


It has aluminum edelbrock heads on it


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## Lemans guy (Oct 14, 2014)

The power valve operates when you need more fuel but your pedal is not down far enough to engage secondaries. Also it will sustain the fuel for however long the demand is, unlike the accelerator pump, which squirts and quits ...the acc pump is a quick shot of fuel for instant acceleration and to prevent a lean bog ...

the power valve would be in play say climbing a long incline but not wide open, also a good place to test it. You need more fuel to get up the incline but your speed is not enough for the secondaries. The PVCR together will add around equivalent of another main fuel jet to the mix.....It comes on when vac drops below the rating of the valve as OMT said,...

I found that the 8.5 gives you power when you need it, the 6.5 was not in play enough for me.

you can bump the total timing to 34 should be very safe there, that is base + centrifugal timing. I set them all at 36 and work from there, only rarely does one have to turn back to 34. And some can take 38 or 40 but you have to watch it closely.

pinging is the sound, it is the detonation inside the cylinder at the improper time and”rings the bell” of the engines steel, it rings. That is what you listen for.


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## Cmeyer9424 (May 5, 2020)

I’ll bump up the timing as well when I install the new power valve. Thanks for the info!


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## Lemans guy (Oct 14, 2014)

Note that when you have the throttle way down the power valve is still pulling and so are the secondaries, the main jets and the idle circuits never stop either, so all can work together at peak demand except for the acc pump which fizzles out in a few seconds...

think of it in stages, first idle circuits up to about 2500 rpm, then main jets come on...

for burst of acceleration, acc pump and for sustained power...first is power valve...as more demand secondaries come on...then everything pulls together.


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## Old Man Taylor (May 9, 2011)

E-heads usually like 36-38 on a 400.


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## BearGFR (Aug 25, 2008)

Cmeyer9424 said:


> It has aluminum edelbrock heads on it


The chamber design can make a difference. The "recent" design E-heads that have the heart shaped chambers (on their D-port and RPM CNC heads, I think) are a little more efficient and may not need as much advance as their earlier heads did. My 72 cc round port RPM's (not CNC) have the regular chambers and seem to be pretty happy at 36.


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## Cmeyer9424 (May 5, 2020)

Just wanted to update on the form, I got the gas smell gone. Went ahead and got an all new exhaust welded in. The old one had so many holes in it from the previous owner trying to weld it up himself. Thanks for all the input👍🏻


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## Droach6498 (Nov 1, 2020)

I purchased my 65 3 months ago and noticed gas smell. Had the exhaust completely redone it helped and installed a fuel reg. as suggested by Edelbrock. No more gas smell.


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