New rebuilt 383.. starts well cold, runs great, doesn't start after warm

[ArtistStan]

My 69 Roadrunner 383 stock stick car had engine rebuilt about 100 miles ago, so it's brand new. The car starts well when cold, runs very well (like new), but once it is warmed up if I turn it off to get gas etc, it won't easily start. I tried giving it no gas, mild gas, holding pedal down and almost ran my battery down trying to start it again. When I brought it back home it smelled a lot like gas in the garage, but that was after driving it 20 miles since the last time it did not easily start.

Vapor locks are often mentioned, but I am open to where to start. It's no fun to not be able to turn the car off for fear that it will not start again. I use 93 octane gas, but have thought of trying an additive in addition, but would like to hear any thoughts any of you have for this. Thanks​

 

[Dennis H]

You are about to be barraged with theories. From impellers to who knows what. Difficult hot re-starts are a Big Block characteristic. If the re-start is within 60 seconds or after 30 minutes, no problem. In between, they are difficult. You can try some things like a spacer under the carb etc. Ethanol fuel makes this problem worse in my opinion. Work on a technique that works. I usually spin the starter, then gradually play with the throttle til it starts. Good luck. 100 miles is not much. Drive the car more, full warm up
and boil out the contaminates.

 

[The Horvaths]

Ethanol sucks.
Carb spacers help reduce thermal coupling between hot intake manifold and carburetor. They can improve low-end torque too. Be sure to use phenolic, or other good non-thermally-conductive spacer. A ball of aluminum foil on the air cleaner will tell you how much clearance you have under the hood.

I step on gas pedal 1/2" to hot-start. Hold it there, no pumping the foot. I don't want accelerator pump to push more fuel into manifold and make things worse.

Be sure that the choke plate isn't closing back down.

Keep fuel lines away from exhaust and insulate if needed. However, if it runs fine once started, vapor lock may not be the main culprit. Did I mention the simple fact that ethanol sucks?

 

[hunt2elk]

A valley pan with the heat crossover blocked off will also help if you didn't already do that.

 

[red 69 runner]

I replaced my Eddy carb with spacer with a Holley and no spacer and problem was solved,also have a valley pan with crossover blocked.

 

[Xp29h]

As stated many possible solutions. However, mine didn't have big troubles starting hot but I replaced valley pan with crossovers blocked and use the gas pedal held in one location not pumped and it starts right up. They always seem to have some sort of starting procedures!

 

[clazar]

I had the same problem with my 6 barrel engine. Turned out the ballast resistor gets hot while driving. It was going bad. Easy on start up then hard starting after shut down. Check it out. Now it starts easy cold & hot. Cheap fix to look at. Plus the junk gas doesn't make our lives easy.

Chuck

 

[Lionized]

I replaced my Eddy carb with spacer with a Holley and no spacer and problem was solved,also have a valley pan with crossover blocked.

Don't want to hijack the thread but I'm having the same issue with My Super Bee. I do have a 1/2" phenolic plate running with an Edelbrock carb. Still have issues. I run 94 Octane exclusively which, up here, is not an Ethanol blend. I also run with no crossover valley pan.

My next step is either running a return line back to the tank or switching out to a Holley. I've already purchased the correct filter (5/16th line with 1/4" return) and my sending unit appears to have a 1/4" capped nipple, which would be great if I could use it for the return line.

Simple question, which Holly are you running?

 

[Dennis H]

Did it with the Carter, does it with the Demon. Not a carb issue on mine. Part characteristic, part fuel, routing of lines. Plus, many have forgotten the old days with new cars that are FI'd and light right up.

 

[mopar 3 B]

Timing, compression, fuel, ignition and exhaust. Get these right and I bet your problem disappears.

 

[Dennis H]

To the OP, I told you we would go all over the planet on remedies. Put more miles on the car. Shakedown is critical.

 

[shorty64]

I imagine you've already considered what's changed with the rebuild (assuming it "re-started" when hot prior to rebuild).
- if it turns over slowly hot, could be tight clearances at bearings, rings, or piston skirts.
- if it turns over same as when "cold", then what's changing during the warm-up?
- any kind/color of smoke out exhaust if it finally starts when hot?
- plugs look wet prior to hot start try?
- more esoteric; coil or ballast resistor going bad?
- other; as per above thoughts?

Anyway, Banachek (George Peppard) and I don't believe in coincidence. So our suggestion is to go back to basics and determine root cause before throwing lots of parts at it.

Good luck regardless.

 

[opus65]

Many times fuel lines have a clamp that bolts the fuel to the front of the right head. Transfers a lot of heat to the fuel and carb.

 

[dieseldazzle]

Same thing my 318 2 barrel in my 67 charger does. I've played with everything and believe the fuel is getting too hot in the carb.

 

[mopar 3 B]

Just check 1 thing at a time. It is just a process of illumination we all go through it. In time you will learn what to look for just by the way things sound and respond. Testing and more testing and do not just start replacing parts eventually you will find the problem. Then fix it.

 

[super-bee_ski]

Latest research is showing that is happening quite a bit.
1. Ethanol in gas will: collect moisture AND EVAP causing these symptoms.
A Recent article by a CARB expert has noticed this happening more and more now.

Why does it "not-affect" your "Modern Car?
Simply because these NEW fuel injected cars are a closed (pressurized) system.
Unlike our Carb fed cars...

 

[Matrix2]

Lots of times hot start problems are due to fuel boiling out of the carburetor. Spacers may help, but I've found in hot climates like mine (I live in the desert), adding an electric fuel pump solves the problem.

 

[ArtistStan]

thanks for all the great help!!! Really appreciated. It seems like the next time I drove it, I kept my foot away from the gas pedal and it started up hot just fine..