hot start problem

1979 Impala - 350 CID V8 crate engine - Edelbrock input manifold - Edelbrock 600 CFM carb - open K&N air cleaner

warm to hot engine has been off for 15-30 minutes with outside temperature 40-50 degrees or higher - depress pedal part way and turn key - engine starts but stalls immediately after pedal release - need to hold pedal down part way for 15-30 seconds after starting for engine not too stall - no problem when turning hot engine off and immediately restarting

A N Y  T H O U G H T S  P L E A S E

Common problem.  It sounds like you're not setting the choke properly.  Depress pedal all the way to the floor and release.  Car should start right up.  If not, the choke is out of adjustment or not functioning properly.
When hot, the choke isn't needed to start the car.

Maybe I didn't make myself clear. Cold start is not a problem. Engines fires right up after setting the choke. Warm to hot start is the problem. In this case, setting the choke to enrich the mixture shouldn't be required. Thanks for your comment.

Sounds like Vapor Lock to me no? Check your return system for any problems (clog ,

bad hose etc). I got a bit of that in hot weather till I replaced all my vacuum lines with

new ones.

All engine related parts are 4-1/2 years and approx. 4000 miles. I have absolutely no emission controls, not even an EGR. So vacuum lines are new and practically nonexistent. Vapor lock is a good suggestion. I know this can happen in a fuel line but do you know if it can be in the carb, fuel filter, or fuel pump? I doubt if the filter is plugged since fuel lines from the tank, and the tank, are also 4-1/2 years and approx. 4000 miles. I always value your comments. Thanks.
P.S. Don't have this problem with my 1978 305 CID Impala with all stock components in the engine bay.

paulboncz wrote:Maybe I didn't make myself clear. Cold start is not a problem. Engines fires right up after setting the choke. Warm to hot start is the problem. In this case, setting the choke to enrich the mixture shouldn't be required. Thanks for your comment.

Oh. Sounded like you were saying cold engine.  
"off for 15-30 minutes with outside temperature 40-50 degrees or higher "

Vapor Lock usually relates to the return Line and stock GM return Lines

are usually tied in with emissions that's why I mention the vacuum lines.

To me its just a carb thing, every carbed vehicle ive ever drove has always done some sort of hard start after warm some worse than others. But then it could be different in your situation, like the choke could start closing after about 10-15 mins. Usually thats about the same time the fuel gets "heat soaked" or sometimes can "boil". Mine does it all the time, it did it with the original quadrajet, the two holleys i put on, the cheap summit racing brand carb i used, and finally on my latest, a quick fuel carb. The better you can get it tuned, and timing plays a role too, the better it will act but again it wont fire up like fuel injection would.

What you have to do is learn the car, and feel it, i know when i let mine site for roughly that same amount of time mine it will have a hard time starting, thats if i dont touch the pedal. but i also dont pump the pedal since its already warm, i just lightly open the throttle and it usually fires up real quick just like it would if it was cold. Those are some of the quirks you get with a carbed car but wouldnt trade it for the world.

I have second thoughts about vapor lock. A long time ago, I used to own a 1965 Corvair which developed a vapor lock. In this case, the engine would crank but not fire. I had to wait an hour or two, depending on the temp, for the engine bay to cool, at which point it would fire up immediately. I never found the vapor lock location.

I try to start my warm to hot engine pretty much as you do. I don't pump the pedal. I depress the throttle slightly and turn the key. The engine fires but runs very rough and stalls after 1 to 3 sec. I can stop the stall by opening the throttle wider for about 30 sec. After which it idles fine. So why am I making a big issue about this? Because I don't need to even touch the gas pedal to start my 78 305 2-Brl (all GM stock) when it is warm or hot.  

I am an old man who likes to cruise not race. So why did I ever get involved with Edelbrock? Give me back my Rochester carb!

P.S. My stock 78 305 2-Brl uses less fuel and is more responsive than my 79 350 4-Brl with Edelbrock input  manifold and carb. I am the original owner of both Impalas.

Thanks to everyone for their comments.