Heat soak - your tips and tricks

[13matsc]

Now that the summer is upon us, the dreaded heat soak is back.

Care to share your tips and tricks for curing it completely or partially?

I still have the issue, especially now with 30* celcius.

I have:

- Covered the starter with heat shield
- Installed heat block off plate between carb and intake
- Wrapped the fuel lines in the engine bay with heat reflective material

To me it seems like the issue is more prevalent when using manifold vacuum for the vacuum advance as the car doesn’t like the 10-ish degrees extra timing when heat soaked.

Any thoughts?

 

[nvrenuf]

What are you working on?

What are the symptoms? (other than outside temp)

 

[Chevy 88]

What are the symptoms of the problem?

 

[fast 99]

Slow starter or hard to start. Sounds like you are attempting to solve 2 different issues.

 

[13matsc]

Not working on anything per se. But now that the outside temperature is high, when I have driven the truck for some time, maybe 30 minutes or so, parked it and then trying to start it again after 15-30 minutes it’s hard to start. Especially if it sat in the sun.

Starter spins like it should, but it behaves like it ran out of gas. Need to pump the pedal several times, key on/off etc and it eventually starts, but a little rough the first seconds.

85 GMC with original 350 engine. Aftermarket intake, carb and headers.
Problem startet when headers were installed a couple of years ago.

 

[Jawzjeep]

I put a phenolic spacer in between my carb and intake. My next step was to make one out of hardwood but the phenolic spacer helped quite a bit. The fuel would just boil out of my carb bowls and make it hard to restart.

I put some open louvers on my Heep hood. Seemed to help a bit with under hood temps.
Good luck to you.

 

[fast 99]

I have basically the same truck and engine. Although it might crank for a couple more seconds will starts just fine.

Use non ethanol fuel

check fuel pump pressure and volume

If fuel level in carb is high that will increase the problem. Didn't say what carb is installed, Holleys seem to be more susceptible to hot soak problems.

 

[nvrenuf]

What carb?
Mechanical or electric fuel pump?

 

[13matsc]

Edelbrock 1406. Mechanical pump.
I’m only running non ethanol fuel.

Fuel line is routed over the valve covers with a filter. Probably not the most ideal placement.
Original radiator and fan.

Electric dual fan with a switch allowing 5 minutes extra running time when shutting her down would probably be ideal.

 

[PrairieDrifter]

Have you tried holding the throttle open while cranking? I've never had a problem with a mechanical clutch fan. Will need to upgrade alt and electrical for electric fans, and for the running after engine shut off you would need an electric water pump for that to work, and a battery sponsor lol

 

[Ricko1966]

Sounds like it's boiling the fuel out of the carb. No problem prior to headers? You are sure? Wrap the headers or put the manifolds back on. Install a pusher pump in the rear on a momentary contact switch. Push the button. Prime the carb,start the truck. In this day and age you can probably find a timed relay,it gets power the relay closes for 10 seconds or so,enough to prime tge system,then business as usually.The pusher pump wouldn't need to run continuallly,just to prime the carb

 

[Frankenchevy]

I believe your problem is Celsius. These trucks run much better in Fahrenheit. (Eagle screeching sound)

 

[nvrenuf]

I’m not familiar with the Edelbrock carbs. I know a problem with older qjets is that they can leak fuel from well plugs into the motor causing a dry carb and a possible flooded condition, is this possible with the Edelbrocks?

 

[fast 99]

Don't need to reinvent the wheel with electric fans. A phenolic spacer might help a little if fuel is boiling. Doubt fuel line insulation will fix it either. Most times vapor lock [if that's what you suspect] is caused by low fuel pressure.

Have not seen Edelbrock carbs leak during storage or hot soak. Evaporate yes, leak no. That is one thing I like about them. Guess that offsets the time it takes to jet one.

 

[Grit dog]

Not working on anything per se. But now that the outside temperature is high, when I have driven the truck for some time, maybe 30 minutes or so, parked it and then trying to start it again after 15-30 minutes it’s hard to start. Especially if it sat in the sun.

Starter spins like it should, but it behaves like it ran out of gas. Need to pump the pedal several times, key on/off etc and it eventually starts, but a little rough the first seconds.

85 GMC with original 350 engine. Aftermarket intake, carb and headers.
Problem startet when headers were installed a couple of years ago.

So is this a 5 second process or a 30 second process?
Both my trucks with Edelbrock carbs, once engine is good and hot if they sit for a bit (up to an hour?? Idk) require a few seconds of cranking to light off. And some of the time they idle real low and want to die for 5-10 seconds until you rev it a couple times. One with mechanical pump and iron manifolds one with electric fuel pump and headers.
Sounds very similar. Haven’t looked into it as it’s not much of an inconvenience but my suspicion is maybe heat boiling some fuel in the carb.
I’d try the carb spacer first.
Also no reason to run non ethanol IMO unless you’re preserving 40 year old rubber fuel hoses somewhere…
Yes ethanol boils lower temp than gasoline but other additives boil at even lower temps. I doubt there’s a big enough difference to matter based on what I’ve read.
If it ain’t vapor locking, the problem is minor IMO.
Plenty of things contribute to underhood temps. Headers being one of them. Janky hot air air filters like on both of mine (as opposed to OE which would pull cooler air if hooked up properly on an 80s truck).

Guess we don’t know how bad the problem is because you’d need to proved some metrics like how long it actually cranks before starting.
And turning the key off and on won’t do a thing unless you’re attempting to push more fuel with a priming timer with an electric pump.
Good luck man!