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Old 08-09-2020, 02:20 PM   #1
tdangle
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Hot restart

Twice now after sitting for 10-15 minutes I restarted and the engine just falls on its face. Similar to it its real cold and not warmed up. 90+ air temp, was running A/C prior to shutoff both times. GM 350/357 performance crate motor, Holley 670 CFM carb. Running a mech fuel pump. After a couple of minutes it is OK. Next time I restart after 10-15 min it is OK. Ideas?
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Old 08-09-2020, 03:20 PM   #2
Greasey Harley
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Re: Hot restart

Carb getting heat soaked?
Are you running ethanol gas? Ethanol can boil at some really low temps. Even non ethanol gas can boil in a hot engine compartment, just not at as low temps.
You might try a phenolic spacer to insulate the carb.
Also, does your fuel line have a return, or does it just "deadhead" at the carb?
Your fuel might be vapor locking between the pump and the carb.
Timing set a little to advanced could cause hot start problems also.
Do you know what your timing is set at?
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Last edited by Greasey Harley; 08-09-2020 at 03:29 PM.
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Old 08-09-2020, 07:49 PM   #3
tdangle
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Re: Hot restart

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Originally Posted by Greasey Harley View Post
Carb getting heat soaked?
Are you running ethanol gas? Ethanol can boil at some really low temps. Even non ethanol gas can boil in a hot engine compartment, just not at as low temps.
You might try a phenolic spacer to insulate the carb.
Also, does your fuel line have a return, or does it just "deadhead" at the carb?
Your fuel might be vapor locking between the pump and the carb.
Timing set a little to advanced could cause hot start problems also.
Do you know what your timing is set at?
Initial timing at 10 with manifold vacuum adding another 10. Total with mechanical advance all in at around 3200 and is 32. No space on carb. mechanical pump with no return. Premium pump gas, Reguar
California stuff. What is weird is it is not repeatable. Last week I made a bunch of short trips running errands and it only did it once. Starts right up, just when accelerating pretty much nothing. That's what has me stumped.
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Old 08-10-2020, 03:04 PM   #4
The Rocknrod
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Re: Hot restart

How old is your carburetor?
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Old 08-10-2020, 04:39 PM   #5
tdangle
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Re: Hot restart

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How old is your carburetor?
New this Feb, it came with the new GM crate motor. Then had it chassis dyno tuned.

I'm wondering if what I experienced is a combination of high underhood heat and the open air cleaner sucking in the hot air. Didn't backfire just stumbled with no power.
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Old 08-10-2020, 04:56 PM   #6
geezer#99
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Re: Hot restart

Use a heat shield like this.
Keeps the bowls cooler.

https://www.holley.com/products/fuel...s/parts/108-70
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Old 08-11-2020, 03:31 PM   #7
garyd1961
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Re: Hot restart

I have the same problem. If I drive long enough to get the good and hot, not overheated but a short drive won't do it, then I shut it off for 20 or 30 minutes it will crank as if flooded. If I crank it right back up after shutting it off it won't do it. If I wait until the motor cools down it won't do it.
I have a L31-R crate motor with a Holley carb and electric fuel pump. I have given up on it but I believe it may have something to do with the electric choke closing and the motor still being warm/hot.
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Old 08-12-2020, 03:14 PM   #8
tdangle
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Re: Hot restart

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Originally Posted by garyd1961 View Post
I have the same problem. If I drive long enough to get the good and hot, not overheated but a short drive won't do it, then I shut it off for 20 or 30 minutes it will crank as if flooded. If I crank it right back up after shutting it off it won't do it. If I wait until the motor cools down it won't do it.
I have a L31-R crate motor with a Holley carb and electric fuel pump. I have given up on it but I believe it may have something to do with the electric choke closing and the motor still being warm/hot.
I was thinking the same thing about the electric choke. Honestly I'm not impressed with it because it doesn't have any real connection to how hot the engine itself is.
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Old 08-12-2020, 09:50 PM   #9
geezer#99
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Re: Hot restart

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I was thinking the same thing about the electric choke. Honestly I'm not impressed with it because it doesn't have any real connection to how hot the engine itself is.
All the more reason to always use a manual choke.
Any other style is never close enough to what you need.
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Old 08-14-2020, 06:09 PM   #10
AcampoDave
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Re: Hot restart

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Originally Posted by garyd1961 View Post
I have the same problem. If I drive long enough to get the good and hot, not overheated but a short drive won't do it, then I shut it off for 20 or 30 minutes it will crank as if flooded. If I crank it right back up after shutting it off it won't do it. If I wait until the motor cools down it won't do it.
I have a L31-R crate motor with a Holley carb and electric fuel pump. I have given up on it but I believe it may have something to do with the electric choke closing and the motor still being warm/hot.
Ditto, with a 283 and a manual choke Eddy carb. I got the palstic spacer even too. Likely too much fuel pressure has some part in it but I just don't care enough to deal with it. I just hold it to the floor when it does that and let up as soon as it fires, then a couple of low revs in neutral and I'm good to go. Edit: Tdangle, maybe its my imagination, but mine seems more prone to hot start trauma if I leave the AC on when i fire it up.

Last edited by AcampoDave; 08-14-2020 at 06:27 PM.
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