Vapor Lock or Bust

[Merrill Davis]

Hello Mopar guys

I have a 340 72 Dodge challenger with new 650 Holley Four Barrel Dual feed with electric choke. It starts great and runs great until I stop and let it sit for awhile. Begin cranking, and it will start running, but then it will die on me and cut off. I wait, depress the pedal a little, hit it again, then it will not crank. Then, I press it to the floor, and it finally starts, but then it dies again. I have let it sit for a spell then try again, this time, when it cranks, hit about 4000 RPM and it finally catches and runs. I am good to go with it then. It is crazy. I put a clothes pin on the metal fuel line but that must be an old wives' tale. It does not work for me. What is happening? How can I fix it. My last question got a fantastic answer and I am very grateful.
I have heard complaints about Holley and friends tell you should have bought a _______. Oh! Well, I purchased the Holley, so here we go. Thank you for any help.

 

[Adam]

Make sure the metal fuel line along the right front is not near the exhaust. Also, a carb spacer may help. And blocking off the manifold carb passages. Nothing wrong with Holley, in my opinion.

 

[tonysrt]

In your 4th sentence you say it won't crank. Then step on gas it cranks. Is it a partial non crank issue. Do you have headers that wrap around the starter. That could be the culprate for the cranking issue. Sounds like 2 different problems.

 

[DetMatt1]

I agree. What are you running for a fuel pump? Today's ethanol laced fuel has a lower boiling point so anything that can be done to insulate the lines from heat or isolate the carb from heat transfer from the engine is a good thing. Fuel additive to combat the negative effects of the ethanol may help a bit too. I added an electric pump back by the tank on my Imperial in the hopes of helping the mechanical pump still in place recover quicker from evaporation.

 

[quapman]

A phenolic carb spacer might help.

What is this clothespin trick you speak of?

 

[DetMatt1]

Some people swear it works while others think it's a myth but wooden clothes pins are supposed to act as a heat soak if attached to the metal fuel line.

 

[Slade Caltrider]

First make sure your steel fuel line is not touching the metal engine block or head any where, will cause heat transfer and a hot spot, carb boil over and severe flooding into the engine intake 5-15 minutes after hot shut off. A good rule is at least a 1/4" space between the steel line and any thing else with engine heat. Make sure your primary and secondary fuel bowl float adjustments are not to high in carb. Make sure you have the factory style insulated carb mounting gasket (1/4" thick)and not a thin gasket. The clothing pin thing does not heat sink but just distrubs and increases the engine fan air flow accross the fuel lines and that pulls more heat from the fuel line. If you want to heat sink a fuel line wrap it in tin foil. Also if running a 192 deg engine thermostat bump it back to a 180 deg stat. Just a few things I always look for. You most likely do have hot shut off carb gas boil over. Just my thoughts from previous experience with this problem.

 

[Steve340]

I had a problem with the electric choke on a 650 ProVac Quickfuel. You do not say if choke wired up? Sounds similar problem. My car would start fine cold but when hot switch it off for 10 minutes or so it would start because of MSD igniton but would blow black smoke for 2 or 3 minutes.
If this sounds familiar I will tell you how to fix it.

 

[Merrill Davis]

Make sure the metal fuel line along the right front is not near the exhaust. Also, a carb spacer may help. And blocking off the manifold carb passages. Nothing wrong with Holley, in my opinion.

Thank you for this Adam. I have a longer metal fuel line and I wondered if that was it. My brother said put a clothes pin on it and I did but it continues to act up. I will persist. Thanks

 

[Merrill Davis]

Thank you for this Adam. I have a longer metal fuel line and I wondered if that was it. My brother said put a clothes pin on it and I did but it continues to act up. I will persist. Thanks

 

[Merrill Davis]

In your 4th sentence you say it won't crank. Then step on gas it cranks. Is it a partial non crank issue. Do you have headers that wrap around the starter. That could be the culprate for the cranking issue. Sounds like 2 different problems.

 

[Merrill Davis]

Thanks Tony. No it will turn the motor over and it will crank but when it starts, it immediately goes down, as if there is no gas, or the motor has just quit. It has no power and it goes down. Weird if you ask me.

 

[Merrill Davis]

I had a problem with the electric choke on a 650 ProVac Quickfuel. You do not say if choke wired up? Sounds similar problem. My car would start fine cold but when hot switch it off for 10 minutes or so it would start because of MSD igniton but would blow black smoke for 2 or 3 minutes.
If this sounds familiar I will tell you how to fix it.

 

[Merrill Davis]

Steve, it does sound quite similar. It sounds like it is all choked up and needs to be BLOWN out. There is an electric choke. It is not manual. Thanks for the response. I know there is a fix. I thought about changing the Carb but some say it is not the carburetor.

 

[Merrill Davis]

First make sure your steel fuel line is not touching the metal engine block or head any where, will cause heat transfer and a hot spot, carb boil over and severe flooding into the engine intake 5-15 minutes after hot shut off. A good rule is at least a 1/4" space between the steel line and any thing else with engine heat. Make sure your primary and secondary fuel bowl float adjustments are not to high in carb. Make sure you have the factory style insulated carb mounting gasket (1/4" thick)and not a thin gasket. The clothing pin thing does not heat sink but just distrubs and increases the engine fan air flow accross the fuel lines and that pulls more heat from the fuel line. If you want to heat sink a fuel line wrap it in tin foil. Also if running a 192 deg engine thermostat bump it back to a 180 deg stat. Just a few things I always look for. You most likely do have hot shut off carb gas boil over. Just my thoughts from previous experience with this problem.

 

[Merrill Davis]

Slade, what an answer. You fellows are just fantastic. It sound just like my problem. The metal gas line IS TOUCHING THE MOTOR! Somehow I will remedy this. My gas filter is at the bottom too instead of near the top. My brother thinks that is a bad idea too. The carb plate is not thin. It is a very nice one that I had to purchase for the new Holley. I suspected that but really from all that I am reading and hearing it is not the issue. Thank you for responding.

 

[Merrill Davis]

Some people swear it works while others think it's a myth but wooden clothes pins are supposed to act as a heat soak if attached to the metal fuel line.

 

[Merrill Davis]

Thanks DetMatt1! I may have been a bit too hasty with my remark. Some swear by it and the more I am hearing, it may make a difference is some cases. Sometimes there are simple answers to a problem demanding a solution. I plan NOT to remove the clothes pin. Take care!

 

[Merrill Davis]

A phenolic carb spacer might help.

What is this clothespin trick you speak of?

 

[Merrill Davis]

Hey! quapman! The clothes pin is a method of transferring heat or taking heat away. I did not take chemistry in school so I may not be using the right language but anyway a number of mechanics swear by it. I plan not to take it off though. Let it ride!!!!