How to Fix Heat Soak in a Carburetor

Heat soak in a carburetor is painfully annoying! What causes the problem, how do you fix it and what are some things to make sure it doesn't cause hot start problems. Doesn't matter if its a Holley, Edelbrock, Quick Fuel or a Quadrajet. This method works on any carburetor to keep the heat away!

#edelbrock #holley #carburetor

[prun]

My anti-vapor lock battle tactics here in Denver, CO (1 mile high and 100F in the summer):
1. An electric fuel pump and pressure regulator and return line.
2. A heavily insulated fuel line in the engine compartment. I use ceramic fiber insulation covered with tin foil tape...don't squish the insulation when taping it. This stuff transfers almost no heat.
3. A tee fitting (the bottom of the tee goes to the carb, the straight of the tee goes back to the gas tank).

1, 2, 3 take care of any hot fuel in the feed line because it's always flowing...no dead head. Any bubbly gas in the lines gets recycled back to the tank before I start a hot engine. Now for the bowls.

4. A non-metal carb spacer (I use a 1/2 inch four hole...my 1 inch open spacer caused a loss of signal and, therefore, a bog).
5. A heat shield mounted under the spacer that extends out under the bowls ( I made my own, but Holley and Edelbrock make them). The top of the heat shield is covered with more taped ceramic fiber insulation for any radiant heat.
6. A 16 inch hole cut into my hood with an electric SPAL fan sucking all the air out of the engine bay for 20 minutes after the engine is turned off or whenever in slow moving traffic.

#6 is a joke. The rest isn't.

[rustywolf]

Interesting, I have a Weber 38/38 on my Jeep 258, every now and then I had issues with it starting, no rhyme or reason, sometimes sitting over night, others for 10 minutes in FL. Filled up with ethanol free, and no issue.

I should also note, many Jeep guys slap on a Weber, and they're running lean without knowing it. Ethanol with 10% gas is around 14.1:1, not 14.7:1, causing even more lean than they were originally. People rarely change what they did 30+ years ago, while unaware how much the gas changed. And not to mention the detergents nowadays.

Good video, subbed!!

[robertswain]

Really thank you for confirming that the rubber composite spacer will work for heat soak as well!

[kgatentumadre]

This guy is awsome. Thank you so much for the tutorial/ teaching videos. Its my first time dealing with a carbureted Ford 302 project car that I bought and its all going well thanks to this channel. (Subscribed)

[og-nxsf]

Have the same prob with a 74 dodge d 200 pick up 360 engine similar edelbrock carb an manifold. I like ur video been learnin about why she runs so good until i stop when its hot out. It will start but but i can tell theres an issue with more difficulty starting while hot. If u add any thickness of spacer u never mentioned having to lengthen the mounting studs. Im surprised longer ones arent included in the spacer kit. Other words say i add a 1 inch spacer. I need to lengthen the studa an inch or usenbolts . Also the return line i have on the oldie is ive noticed is a vent tube . Theres no return line off carb an no regulator to return line with mechanical fuel pump. But all n all its a good truck i paid 650 bucks for it in 2010 an other than normal maintenence & a prt here a prt there. Every day commuter for 13 yrs. Clean body clean interior an rolls straight dwn the road like nobodys buisness. Read a comment lately on unrelated video was " thats what u get for buyin a dodge "Lol prob same guy thats payin 650 a month for 6 yrs an when its ready for the graveyard. My old dodge will still b runnin lol

[CzMnHD]

I put double isolator plates composit. Install vapor removing in line fuel filter and electronic pump. Next thing is installing a small effective fan next to carburator with time based relay after shut off 30 mins. Lets see if I can put more gas to tank and still be able to start my weber. Im a warrior. (also I have fuel return line)

[George]

I have a 71 Caddy with the 472 and original Q-Jet. All stock aside from a Pertronix ignition module and coil, and replaced the original nylon timing gears with a Cloyes steel gear set.

Haven't noticed a hot start issue, but If I sit and idle an excessive amount of time (like at a drive thru, or sitting in traffic), when I go to accelerate back to normal speed, the car stumbles and almost stalls. I can feather the gas to keep moving, and it clears up shortly after and all is well. The car drives fine otherwise. Is this a heat soak issue? Will a spacer help?

[stiliqn]

I may have to do something in relation to this. I have an Aisan with no return line, thats bolted onto the intake with a 1cm or so thick spacer in between, but its also aluminum. For the most part it starts up, but when u turn it off on a hot engine and want to start it up again, its almost impossible. That or it's something to do with the automatic choke. Either way will look into such spacers for mine.

[dieselstuff]

I'm currently running 2 isolator spacers. One between my intake and carb adapter plate and one between my adapter plate and my carburetor. My fuel line is rubber and my fuel filter is orificed. But unfortunately it doesn't work well in my case. The only thing that's helped me is running none ethanol fuel. My issue is Im running a slant 6 so the exhaust manifold bolts directly to the intake floor. So after a good run and at least a 10 min shutdown, it will be hard to start. Heat risers place a big part in the issue along with the ethanol fuel. But sometimes it is just what it is.

[mopardad]

Running plain old rubber fuel line insulated with fiberglass wrap has worked best for me

[Doppps]

Could you depress your foot on the throttle to let the gas soak back in as you would with a flooded carburetor, and turn the key to get her going?

[logcabinautoservice]

could heat soak cause dieseling? ive got a 63' vette with a 327 and an old edelbrock/weber unit and it diesels pretty bad only when hot.

[b-wingman]

What are your thoughts on blocking exhaust cross over ports on intake manifold ? Ok to do in mild climate ?

[jackjenkins]

Hi, I have a 1984 C10 305 V8 Original, Cast Iron Intake, Electric choke, small metal line comes off the exhaust below the exhaust manifold for helping warm up engine( when cold closes when hot opens) works off vacuum on exhaust on passenger side. Has EGR Valve on cast Iron intake, but I have Removed smog control. Will it be safe or important to close off the heat cross over on this cast iron intake before reinstalling? Thanks for info

[einstein]

I did the 1/2 spacer but that was manly for performance.
What I’ve done and it has worked very well is,
1) Relocate the fuel line from the pump to the carb.
A lot of factory installs run the fuel line along the block and the head. Too much heat there.
2) run a 180* thermostat.
Most factory stats are 195*/198* that was many for emissions.
3) the other thing I’ve done was remove the cowl seal at the back of the hood.
I have a hard time getting my engine up to 180* now.
Where I live it gets to the upper 90’s and low 100* days in the summer.


A side note,
When I installed my hood I didn’t have the cowl seals yet.
After I installed them I started having (some) problems with vapor lock. Noting too serious so I uninstalled them and that corrected the problem.

Without the cowl seals that under the hood heat just flows out of the cowl area.
Heat kills

[jimgee]

is a composit spacer better than a aluminum spacer for heat soak ?

[motorvN]

Thanks for this! Is heat soak the same as vapour lock?

[vezina]

do i need to put a gasket between the intake and the heat insulator?

[jerrycordova]

I bought a mechanical fuel pump for my 351W. And it says it's internally regulated, what do you suggest I do about a regulator and return line?

[steverussell]

I have a 65 Impala with a 327 and Rochester carb. I have a hot start problem, starts good cold but shut off for a few minutes and wont start until it cools dowm I plan to install acarb heat spacer on and a fuel filter that vents back to the tank. My question is my fuel tank has only one opening for the tank vent . Could I tee the return lineinto that vent line withoutcausing any problems with the venting?