VAPOR LOCK?

[Joel A Campos]

Hi All,

    I finished my 429 transplant (Still a 429) last fall and cannot get the car to run correctly.  The carburetor, a stock Rochester 4gc was fully dismantled and cleaned and put back together.  car starts and roughly idles but when you put in drive it runs all over itself and will sometimes dies.  Then we get to when it get to operating temp and stalls and will not restart until it cools down.  It will crank over and start on fuel directly in throat of carb, but seems to be starved for fuel otherwise.  

This is an AC car and the Motor swap was from a 64 with AC.

The Fuel filter housing has the vent back to the tank and the tank was replaced with the proper vent return accommodations. I guess I will check that the filter housing is not plugged but not a 100% if its actually Vapor Locking or not? 

I'll be the first to tell you that I am not the greatest at tuning up a vehicle, but any help or direction setting up the carb and other adjustments to fix this condition would be greatly appreciated.

Thanks, 

Joel

[Dennis P. DiBari]

Hi Joel,

     Do you know how your gasoline is - condition wise?  Do you have water in the gas?  When it runs all over itself, it could be bad gas or dirt in the line.  A clogged needle and seat might also cause some of the conditions you described.

Dennis DiBari, NY

[Joel A Campos]

Gas was a fresh fill from a known good station(hopefully).  Car now runs and idles fine but once she heats up to operating temp she dies.  Then it’s hard to start if it does at all.

once it cools down it starts rite back up, until it get to running temperature then we’re into the same scenario.

[Joel A Campos]

other observations/notes:

• A/C car - check return to tank not block.  Checked filter/clear and correct type
• heat riser functional - it does open
• Intake - I have not blocked the heat chock cross over.
• running stock mechanical fuel pump
• Fuel Bowl - does not empty when when condition occurs
• accelerator pump - when throttle moved only see vapor from jets
• engine bay - very warm, will get temp readings to update.

Will Closing off the exhaust cross over and removing the blade from the heat riser eliminate this issue, if this is what is causing the condition?

Will adding a clacker fuel pump back at the tank help any?  If so should that be wired to run continuous or only when it presents this conditions?

Hope all are enjoying the Grand Nationals in Charlotte, NC

[Kenneth Barton]

Hi Joel, how sure are you of the condition of the fuel pump?

I had a pump go out on me and I thought I was fighting vapor lock.

[Joel A Campos]

I do have a new fuel pump I can throw on. Thx will give that a try

[Dennis P. DiBari]

Joel,

     I also sent you a message - check that as well.

Dennis DiBari

[Jeff Donaldson]

Hi Joel,

Did you get this problem sorted?

Jeff

[Joel A Campos]

Not as of today but in the morning I will be pulling the intake to block off the exhaust cross over.  Will also be pulling the exhaust flapper or wiring it open for the time being.

[Jeff Donaldson]

Hi Joel,

I read that you checked the fuel filter so this advice may be useless. I had a 67 Eldorado with the same problem which has the same fuel delivery system. I made the mistake of putting a fuel filter in for a non A/C car. I went through all trouble the shooting you are doing and finally changed the filter to the correct one for a car with A/C. Problem solved. I'm hoping this may help

Jeff

[Joel A Campos]

UPDATE_06/18/2026:

So I believe I have finally figured this situation out.  It was either something in the distributor or it was the ignition coil.  I had an electronic ignition distributor set up with coil that I swapped in and now the old girl will run well past the 20 minute window.  I am 90% sure that once the coil hit a higher temperature, it would short internally and shut down the engine.  I am going to test the old coil soon but the import part is that it’s up and running and able to drive for well more than 20 minutes.

     Thank you to those who took the time to comment as that helped and was greatly appreciated.