# '65 GTO Stalling at > 4000 rpm



## Roqetman (Aug 31, 2015)

Greeting GTO's Experts, I may have asked this question before so forgive me if I did but I'm getting old. I've had my 65 since 2015 and I continue to have a stalling/bogging situation when I try to run 1st or 2nd gear up to 5000 rpm. I've had this same problem from day one and tried 3 different carburetors, a 600 Holley, 600 Edelbrock and 750 Quadrajet which is my preferred carb. The engine runs great until it hits 4000 rpm, above that and it more times than not it bogs down. Sometimes this happens at 4200, or 4500 and sometimes at 5000. I can let off, if I get on it again it might reach 5000 rpm but it will not rev higher than that. It kind of spoils the moment when this happens, it's almost like it has a rev limiter. I feel that the Qjet is tuned correctly, it has a Holley mechanical fuel with 7 pounds of pressure. I don't know if it has a fuel starvation issue or ignition issue. I'm running a GM HEI with a new Delco module. I recently had the engine rebuilt and bored out to 400 ci, it has '69 400 Ram air III heads, hooker long tube headers and mid power range cam that is supposed to be good to 5500 rpm. It has a TH400 tranny and PS, PB and AC. I always turn off the AC when I try these lead-foot runs. Has anyone else had this problem? Any advice on what to check is greatly appreciated. Thank you!


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## RMTZ67 (Mar 12, 2011)

Roqetman said:


> Greeting GTO's Experts, I may have asked this question before so forgive me if I did but I'm getting old. I've had my 65 since 2015 and I continue to have a stalling/bogging situation when I try to run 1st or 2nd gear up to 5000 rpm. I've had this same problem from day one and tried 3 different carburetors, a 600 Holley, 600 Edelbrock and 750 Quadrajet which is my preferred carb. The engine runs great until it hits 4000 rpm, above that and it more times than not it bogs down. Sometimes this happens at 4200, or 4500 and sometimes at 5000. I can let off, if I get on it again it might reach 5000 rpm but it will not rev higher than that. It kind of spoils the moment when this happens, it's almost like it has a rev limiter. I feel that the Qjet is tuned correctly, it has a Holley mechanical fuel with 7 pounds of pressure. I don't know if it has a fuel starvation issue or ignition issue. I'm running a GM HEI with a new Delco module. I recently had the engine rebuilt and bored out to 400 ci, it has '69 400 Ram air III heads, hooker long tube headers and mid power range cam that is supposed to be good to 5500 rpm. It has a TH400 tranny and PS, PB and AC. I always turn off the AC when I try these lead-foot runs. Has anyone else had this problem? Any advice on what to check is greatly appreciated. Thank you!


I kinda still have the same issue. I have replaced my needle and seat with a larger one, fuel pump. Plugs and points, carb pump on the correct holes etc? set my dwell, timing. Timing being last which improved it. But.....still not able to get rid of the bog. Frustrating to say the least. I would not hesitate to lay into it with anybody next to me if I didn't have to worry if it's gonna bog.


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## geeteeohguy (Feb 2, 2008)

I had this issue with my '67 GTO and the first time it was the sock in the fuel tank collapsing causing starvation, and the second time it was a porous rubber fuel line from the tank to the steel line drawing in air but not leaking. You may have a restricted fuel system, leaking hose, or weak fuel pump. Doubt it's a carb since you've had the same symptoms with other carbs and not likely ignition. (but could be). I would start by verifying fuel pressure _and _volume. My gut tells me you are starving for fuel.


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## PontiacJim (Dec 29, 2012)

Sure your tach is accurate and maybe you are pulling more RPM than what it shows? Not the factory tach hooked to the HEI is it?

Gas pedal cable too short or not adjusted correctly so you are not fully opening up the carb?

Fuel filter in backwards on the Q-jet?

Check gas tank breather tube to make sure it is working and not plugged.

12V power source going to the HEI, not the factory resistance wire? What voltage do you have when the car is running.

Bad Alt - not putting out enough charge.

HEI crossfiring within the cap? Do you have a top quality cap/rotor, not the Chinese brand?

Engine/frame grounds?

Gap plugs to .035"?

Swap out the HEI.

Wrong valve springs or improper installed height of the valve springs and you are getting valve float.

Worn cam lobe (s). Improper rocker arm geometry. Wrong length pushrods.

Excessive exhaust back pressure - collapsed muffler or pipe.


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## Lemans guy (Oct 14, 2014)

you may have to gap your plugs a bit closer, .035 even .030….Modules will tend to drop out at very High RPM’s when the gap is too large and they cannot keep up with demand. Pressure in the cylinder has a lot to do with this. In the video attached you can see an example of modules dropping out. Remember that spark in the air is different than spark in a cylinder under 1500 PSI or more. In the air the gap has to be wider to see the strength of the spark. I cm in the air needs 30,000 volts to jump the gap.

You may have a weak module in an old distributor and plugs gap wide. You can see if a new module or distributor and recapping the plugs may help. This company sells Bluetooth enabled distributors.

The HEI were developed for a variety of reasons and could handle very high RPM’s hard to say exactly what these modules are, old, new ….rev limiters would drop the spark as an old weak module will too. Electronics can fail when they are hot, coils do…intermittently and work once again when cool. So it could be many things as the gang has said, you just have to investigate. But with 3 different carbs seems it may not be be that. However your Holley mechanical pump may not be keeping up. I use an edelbrock mechanical pump that provides very strong flow at speed, so check your pump specs as well.


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## Lemans guy (Oct 14, 2014)

Remember also that spark energy has a lot to do with the strength of the coil. A weak coil, yours is in the cap will not keep up the Kilovolts necessary to fire at high Rpm’s. You can see this decline on an oscilloscope as the coil works but not at higher speed. It stalls on demand.

if you have access to an oscilloscope, go to a good garage they all have them, and do a coil stress test. Use non-sparking pliers, and pull one spark plug wire off a plug for just an instant and your waveform will spike to the maximum coil output.
Did one last week and it showed the coil was the culprit………


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## Baaad65 (Aug 29, 2019)

PontiacJim said:


> Sure your tach is accurate and maybe you are pulling more RPM than what it shows? Not the factory tach hooked to the HEI is it?
> 
> Gas pedal cable too short or not adjusted correctly so you are not fully opening up the carb?
> 
> ...


My first post on this site was about this problem and it turned out to be the tach was off, luckily I had a rev limiter because I was hitting the 6000rpm limit but the tach showed 4500-5000, could have been a bad outcome. But I don't think the OP has a limiter.


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## Lemans guy (Oct 14, 2014)

PJ and GeeTeeOhguy gave very comprehensive assessments of possible issues, and I agree with GEETEE on the 3 carbs….so it will take some work to discover what is what, but you have to know some places to look. And they laid that out, I added in a possible ignition reason which they talked about as well….fuel volume may be dropping off and that will give you the stall as GEETEE mentioned…


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## armyadarkness (Dec 7, 2020)

Now Im curious...

I hit my rev limiter a few times when I down shift the TH400 and wail on it. Im sure I only set it at 5000 or less.

What "is" a good racing RPM to shift a full roller 400, 670 heads, Ram Air cam at?


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## Lemans guy (Oct 14, 2014)

We need the racers to weigh in on that, Mr. Taylor Big D, Bear and Pand others. Just when you are hitting those RPM’s frequently a good strong coil and ignition system in top condition is needed, and the wider the plug gap the move kv it takes to jump the gap at speed.

What happens is both the switch whether points or electronic has less time for the coil to build power during the dwell period. Points close or electronic switch which allows the primary coil winding to build a reserve of electromagnetism. When the points or transistor opens that collapses thru the secondary windings and reaches Kv’s of 30 to 50 Kv.

Now I know you know all this but it pays to picture it in your mind to visuze how you lose the spark. Points are limited by physics and their mechanical ability to remain closed at high RPM’s. Points float happens.

Electronic switches, Hall effect, optical, lobe sensing do better by having the ability to vary the dwell, but they too have to deal with the high speed. We don’t know the conditions of the coils or modules in the video. Generally your electronic module will perform adequately if ignition system is in good condition.


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## Lemans guy (Oct 14, 2014)

Bear and PJ…sorry typo


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## Sick467 (Oct 29, 2019)

My old Pontiac would "level off" if I pushed the redline so to speak. I never had a tach, but when manual shifting up through the auto gears and obviously near destruction...the old engine would not produce more pull. It did not feel like a stall or loss of power, just would not produce any more. I think the stock upper end could not allow any more air to be sucked in acting like a bottle neck and limiting the RPM's. It's just my theory, but I'm glad it was like that or I would have surely blown it up. 

I'd verify your tach first, but, DANG, you've got some good advice already!


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## Roqetman (Aug 31, 2015)

geeteeohguy said:


> I had this issue with my '67 GTO and the first time it was the sock in the fuel tank collapsing causing starvation, and the second time it was a porous rubber fuel line from the tank to the steel line drawing in air but not leaking. You may have a restricted fuel system, leaking hose, or weak fuel pump. Doubt it's a carb since you've had the same symptoms with other carbs and not likely ignition. (but could be). I would start by verifying fuel pressure _and _volume. My gut tells me you are starving for fuel.


We checked the fuel pressure and it shows 7 psi. Fuel line hoses are all good. The sending unit in tank is new so the sock should be ok.


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## Roqetman (Aug 31, 2015)

Baaad65 said:


> My first post on this site was about this problem and it turned out to be the tach was off, luckily I had a rev limiter because I was hitting the 6000rpm limit but the tach showed 4500-5000, could have been a bad outcome. But I don't think the OP has a limiter.





Baaad65 said:


> My first post on this site was about this problem and it turned out to be the tach was off, luckily I had a rev limiter because I was hitting the 6000rpm limit but the tach showed 4500-5000, could have been a bad outcome. But I don't think the OP has a limiter.





armyadarkness said:


> Now Im curious...
> 
> I hit my rev limiter a few times when I down shift the TH400 and wail on it. Im sure I only set it at 5000 or less.
> 
> What "is" a good racing RPM to shift a full roller 400, 670 heads, Ram Air cam at?


 It does not have a rev limiter that I know of. The GM Hei is stock with a new Delco module.


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## Roqetman (Aug 31, 2015)

Baaad65 said:


> My first post on this site was about this problem and it turned out to be the tach was off, luckily I had a rev limiter because I was hitting the 6000rpm limit but the tach showed 4500-5000, could have been a bad outcome. But I don't think the OP has a limiter.


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## Roqetman (Aug 31, 2015)

PontiacJim said:


> Sure your tach is accurate and maybe you are pulling more RPM than what it shows? Not the factory tach hooked to the HEI is it?
> 
> Gas pedal cable too short or not adjusted correctly so you are not fully opening up the carb?
> 
> ...





PontiacJim said:


> Sure your tach is accurate and maybe you are pulling more RPM than what it shows? Not the factory tach hooked to the HEI is it?
> 
> Gas pedal cable too short or not adjusted correctly so you are not fully opening up the carb?
> 
> ...


The tach is a reproduction in-dash tach designed for HEI, it does a full sweep on start up. I had the same problem with the old Stewart-Warner tach. I put a vented gas cap on and seemed to help some but not enough. 12v to HEI is good. Alternator is relatively new but it’s a stock replacement, not high output. Cap and rotor are good quality with brass contacts. I was wondering what would be a good replacement distributor/coil, any recommendations on what would be compatible? Cam and pushrods are good. Exhaust system is all good. Me thinks it’s the ignition. I’ll see about having the distribution checked out. Thanks for your input. Lots of things to check.


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## Roqetman (Aug 31, 2015)

Lemans guy said:


> you may have to gap your plugs a bit closer, .035 even .030….Modules will tend to drop out at very High RPM’s when the gap is too large and they cannot keep up with demand. Pressure in the cylinder has a lot to do with this. In the video attached you can see an example of modules dropping out. Remember that spark in the air is different than spark in a cylinder under 1500 PSI or more. In the air the gap has to be wider to see the strength of the spark. I cm in the air needs 30,000 volts to jump the gap.
> 
> You may have a weak module in an old distributor and plugs gap wide. You can see if a new module or distributor and recapping the plugs may help. This company sells Bluetooth enabled distributors.
> 
> The HEI were developed for a variety of reasons and could handle very high RPM’s hard to say exactly what these modules are, old, new ….rev limiters would drop the spark as an old weak module will too. Electronics can fail when they are hot, coils do…intermittently and work once again when cool. So it could be many things as the gang has said, you just have to investigate. But with 3 different carbs seems it may not be be that. However your Holley mechanical pump may not be keeping up. I use an edelbrock mechanical pump that provides very strong flow at speed, so check your pump specs as well.


The video is very interesting but… the ground has been removed from the plugs and the arc is much wider that what would be on a standard gapped plug. It would interesting to see the same test with correcting gapped plugs and see if the GM HEI still breaks down. Thanks for sharing.


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## Lemans guy (Oct 14, 2014)

It won’t work that way, plugs will fire in the air at atmospheric pressure very easily. Much different in a cylinder under 1500 or more PSI. That is why the distance is needed, the distance is necessary to “try” to replicate that. Yes this is a standard type set-up for observing spark outside the cylinder, a pressure chamber is better.

the wider gap requires more kilovolts from the coil. Here the center rod is the ground and the side tips of spark plugs cut off just to show the spark in air.


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## PontiacJim (Dec 29, 2012)

Roqetman said:


> The tach is a reproduction in-dash tach designed for HEI, it does a full sweep on start up. I had the same problem with the old Stewart-Warner tach. I put a vented gas cap on and seemed to help some but not enough. 12v to HEI is good. Alternator is relatively new but it’s a stock replacement, not high output. Cap and rotor are good quality with brass contacts. I was wondering what would be a good replacement distributor/coil, any recommendations on what would be compatible? Cam and pushrods are good. Exhaust system is all good. Me thinks it’s the ignition. I’ll see about having the distribution checked out. Thanks for your input. Lots of things to check.


From an article online, MotorTrend:

"Early HEIs were infamous for giving up at speeds above 5,000 rpm-so many avoided them. The advance curve on a stock HEI is for the most part not fully advanced until 4,000-4,500 rpm, which is very slow. If your low-end cam power band begins at 2,500 rpm (or below), then your advance curve will not be matched to your camshafts power-band, which will result in a significant horsepower/torque loss."

If you have to keep the HEI, then I think it might be easier to send it out and have it checked and set-up so that rules out your problems.


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## coyote595 (Dec 4, 2019)

I remember back in the 80's Accel made an "HEI Intensifier Kit". It divorced the coil from the distributor, and you used an Accel Super Coil instead. If I remember their advertising correctly, they claimed that at higher RPMs, the spark could seek ground through the mechanical advance and act as an unplanned rev limiter. I did buy this kit, and had no problem with it, but I cannot validate their claims, as I did this mod right off the bat, so never experienced the "problem". The engine would rev freely to about 6800 rpm with that set up. After a couple of years I switched to a Mallory Unilite, which I really liked and never had a problem with. Still have it actually, just not using it in anything right now.


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## Roqetman (Aug 31, 2015)

Lemans guy said:


> It won’t work that way, plugs will fire in the air at atmospheric pressure very easily. Much different in a cylinder under 1500 or more PSI. That is why the distance is needed, the distance is necessary to “try” to replicate that. Yes this is a standard type set-up for observing spark outside the cylinder, a pressure chamber is better.
> 
> the wider gap requires more kilovolts from the coil. Here the center rod is the ground and the side tips of spark plugs cut off just to show the spark in air.
> 
> Ok, Thanks for the clarification!


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## Roqetman (Aug 31, 2015)

PontiacJim said:


> From an article online, MotorTrend:
> 
> "Early HEIs were infamous for giving up at speeds above 5,000 rpm-so many avoided them. The advance curve on a stock HEI is for the most part not fully advanced until 4,000-4,500 rpm, which is very slow. If your low-end cam power band begins at 2,500 rpm (or below), then your advance curve will not be matched to your camshafts power-band, which will result in a significant horsepower/torque loss."
> 
> If you have to keep the HEI, then I think it might be easier to send it out and have it checked and set-up so that rules out your problems.


I’m not locked into the GM HEI. What would be a good electronic ignition replacement? I don’t want to have an external spark box. I prefer a plug and play. I could buy a stock distributor and use a Pertronix module and coil. Any thoughts on this or other distributors like MSD, DUI, Pertronix, etc…?


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## geeteeohguy (Feb 2, 2008)

I've been running stock points and condenser OEM distributors for the past 45 years with zero issues and hundreds of thousands of miles. They are dependable, and sacrifice no power loss to an HEI. Lots of younger guys don't like them because they don't understand them and think that they are trouble prone due to lack of experience with them. I replace mine with good NOS units at every 15k miles or so. Have seen more failed HEI's I can count, particularly Pertronix units, but also the others, including the OEM's. It would be interesting to see how your car runs with a stock distributor. You checked fuel pressure----but did you check VOLUME?


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## PontiacJim (Dec 29, 2012)

Roqetman said:


> I’m not locked into the GM HEI. What would be a good electronic ignition replacement? I don’t want to have an external spark box. I prefer a plug and play. I could buy a stock distributor and use a Pertronix module and coil. Any thoughts on this or other distributors like MSD, DUI, Pertronix, etc…?


You have several options. You can get a stock points type distributor and add the Pertronix conversion. I did that on the 400CI build I had put in '68 Lemans. I had no issues with it, but it did require 12V which I had wired up to a toggle switch that by-passed the resistor wire (cheap backyard fix). I could tell when I forgot to flip the switch - the engine responsiveness seemed a little less "sharp." The problem with the Pertronix conversions were the early ones and once they failed and the failures were posted on the assorted forums, they got a bad rap and it still carries forward by those who use those old posts and are stuck in the past.

I also have/did a Pertronix conversion in the factory 1948 International flathead 6-cyl to make maintenance easier and not having to source points/condensors for a vehicle of this age. I converted the 6V postive ground wiring system over to a 12V negative ground and Pertronix had the conversion kit. Runs smooth as silk.

The issue was that the modules would burn up/out if you left the ignition switch in the "Run" position, ie to listen to your radio with the engine off, or prolonged use diagnosing an electrical problem. They required 12V even though the instructions stated will work on 12V or with the resistor wire at reduced voltage, but I feel they needed the 12V to operate correctly and my toggle switch proved this to me. From the Pertronix website:

"With Ignitor electronic ignition systems, leaving the ignition switch in the run position when the engine is not running, can cause permanent damage to the ignition system, and related components. This does not apply to the accessory position of the ignition switch. Ignitor II and Ignitor III ignition systems have protections built into them that turn off the system prior to damage."

Points work fine if you don't mind keeping up with them as they wear - checking gap/dwell, and then replacing them as part of regular maintenance. When the points begin to go "south" you usually can tell as the engine doesn't run "peak." Points can also corrode/oxidize if the car sits long periods and the engine not run in places around the country that have high humidity/moisture or seasonal changes - far less of an issue for cars kept garaged, never been a issue for me when driven daily. Replacement points/condensors don't seem to have a very good reputation anymore than the early Pertronix conversions did as most are made overseas and junk. Getting a "good" set usually means finding an NOS Delco or AC set of points and condensor on Ebay or other venue.

With an electronic distributor, when the module fails, it just flat out quits with no notice and you are stuck wherever that is. But there is no gapping points, setting dwell, or installing new points every "X" miles - so you can go 100,000 miles plus and only have to do the cap/rotor change - short of replacing wires or a coil which can also crop up with a points distributor. The electronic distributor have far more features that a points distributor does not such as RPM limiting, hotter starting voltage, adaptive dwell (dwell changes with RPM to maximize power), more timing accuracy and you don't have to worry about "point bounce" at higher RPM's which some of the Chinese points do at lower RPM's. They even are capable of being adjusted by your I-phone if you are a techy type.

Scroll down the Pertronix page to see the comparisons between points and electronic distributors. I am using the Pertronix Ignitor II plug and play distributor and matching coil in my 455 build. Not saying you have to go with Pertronix as there are other makes that will work equally well and for less money.









PerTronix Electronic Ignition Points Conversion Kit | Never Replace Points Again


PerTronix Electronic Ignition Points Conversion Kit are the the best-selling electronic ignition conversions on the market. Easy to install.




pertronixbrands.com


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## Lemans guy (Oct 14, 2014)

Well said by all, whatever you decide use quality parts and keep everything in good shape. Had a Petronix II module quit once…..but it wasn’t the module. Too much crankcase pressure had forced too much oil up the small oil lubricating holes in the bottom body of the distributor.

The oil coated the magnet ring and Petronix would no fire. Probably would have killed points too. All things are machines or electronics and all can fail. But I would be afraid of any of them, points, HEI, Petronix etc.

Cheap parts ain’t Good and Good parts ain’t cheap…….


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## PontiacJim (Dec 29, 2012)

Roqetman said:


> I’m not locked into the GM HEI. What would be a good electronic ignition replacement? I don’t want to have an external spark box. I prefer a plug and play. I could buy a stock distributor and use a Pertronix module and coil. Any thoughts on this or other distributors like MSD, DUI, Pertronix, etc…?


I don't know if this has been brought up or if you have looked into this. We had a forum member who was having fuel delivery issues and checked/replaced several items without success. He decided to "back flush" his gas lines unhooking the lines from the fuel pump and tank and then blew compressed air through the line. Sure enough, he heard a pop as something that had lodged in the line let loose. He reconnected his gas lines and his problem was fixed.

So don't discount that a small chunk of rubber hose at the rear connect at the tank could have sheared off or broken loose from the rubber hose and gotten sucked down into the metal gas line at some point in the cars life. Ethanol fuels will cause the original non-ethanol friendly rubber to swell and even separate so it can break off and go floating down the gas line plugging it up. The same goes for the factory "sock" filter on the end of the pick-up tube in the tank. It can harden over time and it is made of a nylon material that crumbles and breaks up in pieces and could also be sucked into the gas line and plug it up. These two items are before your pump and filter and there is nothing to trap or stop them from entering the steel gas line and plugging or restricting gas flow to the engine.

The other thing to check is make sure new ethanol friendly rubber gas line at both the rear connection at the tank and up front at the fuel pump. Again, I have experienced 1st hand that the old rubber type hose will swell and eventually split. The swelling can also choke the fuel flow as it narrows the hose diameter on the inside. You can also have a split or loose hose clamp that does not show up until your engine demands the higher flow required at the higher RPM's. At lower RPM's you may not notice this as the fuel flow and fuel requirements are more "lazy." I always use the higher PSI rubber fuel line used on the newer cars with fuel injection as these seem to work much better and are guaranteed to be ethanol friendly - but my experience is that you have to ask for it otherwise I have been given the lower grade gas hose that doesn't seem to be ethanol friendly even though the parts counter person says it is.

I still am not a fan of the factory HEI distributors and there is no guarantee that if you change it out that your issue will be solved. So check all your lines and connections to make sure it is not a fuel flow problem. Personally, I would not have an issue ditching the HEI for another aftermarket electronic type distributor even if it did not resolve my problem, but I don't want to see you swap it out and then get annoyed at our recommendations because you spent good money where maybe you did not have to. Money doesn't grow on trees, at least in my neck of the woods and I have been looking for that tree all my life.


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## geeteeohguy (Feb 2, 2008)

A good friend of mine runs Pertonix on every old GM car he has. Put one on the '65 El Camino we just put a 383 stroker in. Left him stranded in the first two weeks of operation on a test drive. But, most folks prefer HEI to points. Who wants the hassle of changing them every 15,ooo miles. To most of us, that would be once every 5 years. To some of us, it would be decades. Very inconvenient.


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## Dave 68 (Nov 18, 2018)

I had same issue, I found out the sock on the fuel pick up was collapsed, keeping the pump from getting enough volume to the carb. Everything checked out while in the driveway, but under load it starved. Dropped the tank and replaced the entire sending unit, added an electric pump, and the problem went away.


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## Dave 68 (Nov 18, 2018)

And if you're thinking it's a distributer problem with HEI, I installed a circuit breaker and relay at the battery to supply mine with the full 12 volt, maximum amps it needs. The original switched power supply controls the relay, so it's on with key, off with key.


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## geeteeohguy (Feb 2, 2008)

Dave 68 said:


> I had same issue, I found out the sock on the fuel pick up was collapsed, keeping the pump from getting enough volume to the carb. Everything checked out while in the driveway, but under load it starved. Dropped the tank and replaced the entire sending unit, added an electric pump, and the problem went away.


I mentioned this on post #3 of this thread but it was discounted as the OP has a new sock and pickup, supposedly. I chased a collapsed-sock issue on my '67 GTO on a vacation back in the 1980's from CA to Yellowstone National Park and back. That was a long, hot trip. Blowing out the fuel lines every 50 miles or so with my mouth. Enough to straighten out the sock like a party favor and get fuel for a few more miles before it collapsed on itself again. When I got home I cut the sock off and have been running a bare pickup tube ever since. That was 34 years and 90,000 miles ago with no issues.


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## @2018 Mardi (Jun 2, 2021)

I had a 75 T/A 400 with factory HEI. Same thing, it would crap out at around 4500. That HEI had the coil mounted in the distributor cap.
Turned out that the rotor, or something, was arcing through the cap to one of the four metal screws holding down the coil. It would actually melt a hole through the cap. Took a while to figure it out however, I guess it was common enough for H-O Racing Specialties to offer nylon coil mounting screws. Solved the problem.


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## Lemans guy (Oct 14, 2014)

Yes a great point, you can take off the coil in cap and inspect the underside, look for carbon tracking, black spots leading to any one of the mounting screws, it could only are at certain RPM because the sparks stretch out from the rotor tips to the cap tips as the weights go out and advance the spark and RPM’s increase


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## coyote595 (Dec 4, 2019)

Yes, this is what I was mentioning in post #20. Accel's solution at the time was to eliminate the Coil-In-Cap altogether and keep the HEI, but with an external coil.


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## Roqetman (Aug 31, 2015)

I’ve been out of town for 9 days but I am going to check fuel volume and blow out the fuel line first chance I get. Thanks!


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## Roqetman (Aug 31, 2015)

Pontiac Jim, thanks for the great information! I also have a ’72 Cutlass, stock 350, 750 Qjet and years ago the points gave up and left me stranded. Granted, I did not know how long they had been installed as they were installed by previous owner and it ran great until it quit. Since then, I’ve been using Pertronix module with the stock distributor without issue and it will rev to 5000 rpm without any hiccups. So that set up that might be an option for the GTO. I just checked the voltage on the GTO HEI and it’s getting 14.4 volts with engine running, 12.5 v with just the switch on, not running. I’m going to blow out the fuel line and check fuel pump volume. If that doesn’t fix it I’m going to put a new electronic distributor in it and hope that fixes it. The GTO’s 389 engine has been bored to 400 ci with 400 RAIII heads, headers, Edelbrock intake and 750 Qjet and it does wind-up fast and quick until it gets over 4000 rpm. I’m wondering if the float bowels are big enough to keep up with this set up?


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## Roqetman (Aug 31, 2015)

PS: I know some have commented on this post that points work fine and no more than my cars get driven that’s likely true but I feel electronic ignition is a technological improvement, kind of like disc brakes and halogen headlights. Plus I hate installing them an checking the gap and dwell. I can do it but I‘d rather not.


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## Roqetman (Aug 31, 2015)

As a follow up to my post about engine stalling >4,000 rpm. Good News! I think we found the problem and it was an easy fix. I took the guy that rebuilt the engine for a test drive yesterday and as expected the engine would stall out >4000 rpm. He said that because it happens so abruptly that he thought it was an electrical problem and not a fuel delivery problem. When we got back he looked at the relay on the firewall that provides power to the GM HEI. The relay was grounded to the firewall with a small wire and screw. He recommended I install a better ground to the engine. This morning I installed a heavy gauge ground wire from the relay to the engine and voilà the problem is solved! It now reaches >5000 rpm with no issues! Understand, the engine builder did not re-install the engine as another shop did that put all the connections back as before. This problem has be going for years and illustrates the importance of proper grounds and… getting a second opinion. Hopefully this will help others having this problem. Thanks again for all the comments and suggestions!


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## Baaad65 (Aug 29, 2019)

Roqetman said:


> As a follow up to my post about engine stalling >4,000 rpm. Good News! I think we found the problem and it was an easy fix. I took the guy that rebuilt the engine for a test drive yesterday and as expected the engine would stall out >4000 rpm. He said that because it happens so abruptly that he thought it was an electrical problem and not a fuel delivery problem. When we got back he looked at the relay on the firewall that provides power to the GM HEI. The relay was grounded to the firewall with a small wire and screw. He recommended I install a better ground to the engine. This morning I installed a heavy gauge ground wire from the relay to the engine and voilà the problem is solved! It now reaches >5000 rpm with no issues! Understand, the engine builder did not re-install the engine as another shop did that put all the connections back as before. This problem has be going for years and illustrates the importance of proper grounds and… getting a second opinion. Hopefully this will help others having this problem. Thanks again for all the comments and suggestions!


Like I said somewhere else, bad grounds are the root of most electrical problems and also maybe why army's car is too quiet


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## geeteeohguy (Feb 2, 2008)

Yet another incident where the 'upgrade' to HEI introduced a problem that would not have occurred with the stock, stone-age ignition system. But, it's all about having fun with our cars and I am glad you found the issue.


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## Lemans guy (Oct 14, 2014)

When any demand is high on any electrical circuit they can fail if not properly set up or if, resistance builds, or if components wear down. Like solenoids and alternators for example.

Heat also plays a role because it increases resistance in the circuit. Like when your starter is too close to the exhaust manifold…

so good find, good work..


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## Lemans guy (Oct 14, 2014)

Your weak ground worked …until demand increased, then it failed. The circuit could not deliver.this happens often on misfires, at idle they will not show on the oscilloscope…

but once the throttle is snapped and demand increases, the scope will pick up the misfire. Spark fires fine when demand is light….but fails when demand increases..


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## Roqetman (Aug 31, 2015)

First of all thanks for all the input and support. After further testing and driving the stalling issue is not resolved. After replacing the ground wire I thought the stalling problem was fixed but it’s not… it’s acting up and still stalling out >4000. One mechanic thought is was ignition due to the ground wire another mechanic thinks it’s fuel delivery. The Qjet is off a ‘70 Olds 350 that I have re-jetted and changed the secondary rods and idle circuit. If it is fuel delivery then this carb is not keeping up with demand. Can it be reconfigured for a ‘69 400 RAIII? If so, where can I find the specs? If not what a good replacement carb for this setup? The ignition is GM HEI from the mid 70’s. If it is ignition, what type and brand is recommended for this set up? This 389 has been bored 60 over making it a 400 ci and it has 69 RAIII heads. My thought is I may need a new ignition system and carb to for a ‘69 400 RAIII to resolve this stalling issue.


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## RMTZ67 (Mar 12, 2011)

Been awhile since I read your posts, but wondering if you tried advancing your timing some, already? I had a high end bog as well, tried many things w/o success. Finally advanced my timing which made a huge improvement.


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## geeteeohguy (Feb 2, 2008)

Advancing timing will typically hurt top end and help bottom end.


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## RMTZ67 (Mar 12, 2011)

geeteeohguy said:


> Advancing timing will typically hurt top end and help bottom end.


I believe I went like 2 degrees advance and seemed to help when nothing else I tried would (????) High flow needle and seat, raise the float, new filter, no filter, set mixture screws with vacuum gauge and on and on. But you are right, when I punch it in third it doesnt seem to have as much go.


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