Heat Soak

[JWestfall]

I have a 71 Wagoneer with a 360, Edelbrock performer intake and 1406 carb. Heat soak floods it after sitting for 10-15+ minutes. I have tried everything to eliminate the problem because it drives me nuts. I have installed an insulated carb spacer, blocked the exhaust cross-over, lowered float bowl level (and it has offroad needle and seats, although I don't think this is a factor). I run a 195 Thermostat. If I run a 180 it helps, but then my heater is less affective. I live in California, so I can only get 10% ethanol fuel. Am I missing something or do I just need to live with it or get EFI. It's more of an annoyance than a problem, and the Jeep runs great otherwise.
Thanks for the help.

[Stuka]

What are the symptoms that you are seeing? Is it vapor locking?

Something worth looking at is the fuel line routing, if vapor lock is your issue. If the hard line is getting too hot, it will boil the fuel before it even gets to the carb.

[JWestfall]

My fuel lines are routed away from exhaust and wrapped with fuel the insulating tape. Running an electric fuel pump mounted on the frame by the gas tank with a regulator (4.5 psi) and return line. Symptoms: when cold or after sitting for <5 minutes, starts instantly and runs great. When sitting for more than that after getting up to running temp, it takes about 5 seconds of cranking to start. Not a strong smell of gas, however.
Thanks

[letank]

Can you run the electric fuel pump for 5 sec without cranking the engine?

My fuel filter is installed on the inner fender away from exhaust heat, more or less aligned with the hood strut on driver side, next to the ignition module.

FSJfuelLine85x.jpg

this is an old pict, here the metal return line is still plumbed, but was later removed

[JWestfall]

I can run the pump without cranking. Is it possible I'm looking at this backwards; that it's fuel starved instead of flooded? And my fuel filter is on the firewall above the brake booster.
Thanks

[Mopar_guy]

Very common issue with Edelbrock carbs. How thick is the spacer? I would have a 1" or thicker on it. I had the same issue on the 304 I had. I got fed up eventually and switched to FI.

[OldFarmTruck22]

That 'insulation' is not helping you. Get the DEI or others that is made for fuel line. It has a fiberglass weave inner structure with a REFLECTIVE foil outer skin. It Velcros around the fuel line. Your method is actually holding heat in.

[JWestfall]

That's what I have. I just didn't call it the right thing.

[tgreese]

Add louvers in the hood? This is a hot rod thing, and a local club could probably direct you to a shop or individual that can add louvers.



I don't recall anyone doing this, but maybe you could add fins to your carb spacer. Layers of aluminum between phenolic spacers, with the aluminum protruding as fins to dissipate heat. There are also carb spacers with coolant running though, that possibly could dissipate heat after shutdown. I think these mostly warm the manifold top and carb base for better cold weather drivability, but they might have benefit in moderating the carb temp after shutdown. Junkyard item.

[letank]

I can run the pump without cranking. Is it possible I'm looking at this backwards; that it's fuel starved instead of flooded? And my fuel filter is on the firewall above the brake booster.
Thanks

Start with the easiest troubleshooting method, run the fuel pump for 5 sec, then crank.

As for heat soaking and louver, there are quick alternates, pop some wood sticks under the hood at the cowl to keep the hood from completely closing... you can see the louver style on the hood in the background

hoodsticks3.jpg

and here

louvers.jpg

otherwise you can buy louver bits and cut a large hole in the hood, or a more elegant way would be to put a slit on the top part of the fender like it can be seen on a few late models such as Land rover that are in junkyard or on line

LR4sideVents.png

[JWestfall]

Thanks for all the tips. I will try letting the fuel pump run for a few seconds before starting. If that doesn't do it, I think I will live with it or bite the bullet one day on do EFI.

[tgreese]

You can buy bolt-on (as in the pictures above) or weld-in louver panels. Check Summit or Speedway. A hot rod shop likely has a press punch/die that will put louvers in an existing panel.

[letank]

IIRC these are the one used on the waggy

https://genright.com/categories/product ... uvers.html

genright.png

My plan was to cut off the LR3 that I bought at the JY at the center seam and put one on each side of the fender... at least start with one side, the advantage being no water intrusion from above

LR3vent.png

much cheaper at the junkyard....

https://forums.ifsja.org/forum/tire-kic ... ouver-talk

[devildog80]

I ask......was the heat soak an issue when these trucks were new?
Does not seem to be with anything I have read, so seems to become a problem when we work to revive the rigs? But with everything back to OEM, it is now an issue?
I too have all my fuel lines run away from any heat sources, thermal riser on carb, and mine also is a hard start after sitting for a few minutes. Running the electric pump for a few seconds before warm start makes no difference, and do not believe there is any vapor lock, so attribute it to rebuilt engine compression?
But again......why not an original issue when trucks were new?

Temporary rubber/metal fuel line with return up with plenty of air flow.
20231217_111032 by Scott Weckerly, on Flickr

[Yeller]

fuel is different, methanol and other additives lower the boiling point, increasing the risk of vapor lock. Also it is possible to have more restriction due to it being old from the pick up screen in the tank, additional fuel filters, etc., fuel under vacuum boils at an even lower temperature, it is exponential and surprising how low of a temp it will boil.

[tgreese]

Heat soak is an imprecise and broad term. I would define it as fuel boiling in the carburetor, not vapor lock. With an electric fuel pump, this Jeep should not suffer from vapor lock.

I wonder how much of any boiling is related to the design of the carburetor. Looks like the Edelbrock uses a removable bowl, like a Holley. The body casting includes the bowl with the Motorcraft carbs. You could argue that the Motorcraft design conducts heat away from the bowl more effectively ... possible. However, you could - as plausibly - argue that the isolated bowl absorbs less heat from the carb body. Hard to say without measurements. If you had an example of each, you could run them both hard and measure the bowl temperature of both (a laser thermometer, or cell phone thermal camera would work), and get closer to an answer. I suspect the carburetor design plays a significant role.

[devildog80]

Ok, so the OEM 2 bbl carbs used were the MC2150 on my '84 GW. As all is set to run at OEM spec, except the 401 engine vs original 360 engine, but all other pieces/parts OEM. I would think there should be no hard start after full operating temp just light city driving to the store, then sit for 10-15 minutes.

TA has a slightly different setup with his '71, but nothing really out of the norm for these old trucks, compared to OEM. So thinking he should not be having the same issue, but seems to have identical issue. Could it be as simple as different type fuel from OEM to now causing these type issues?

[letank]

fuel is different, methanol and other additives lower the boiling point, increasing the risk of vapor lock.

X2,

Travelling in Arizona in the summer... I never bothered to pop up the hood to cool the carb in the 80's to early 90's... engine would start and restart without issues... it was the early year, barely 100Kmiles.

[devildog80]

Still healing from sore rib & mucous cruds, so 4 bbl has not been installed yet on my '84 GW, but considering venting the hood for operating year around here in AZ desert. My Jeep partner in crime put some external louvers on his '80 CJ7 w/360 engine, and seems to help with his rear facing louvers, so thinking of doing the same with my GW. Vents he put on (look just like the ones above) his would fit perfectly on GW hood, and were reasonably priced.
Now due to air flow in engine well, better to position the louvers to face the front, or towards the back? My primary use will be road miles, not trail, so forward would bring in more air while driving....to aid flow down under the truck? To the rear would draw more air out through the hood while driving? Running an Edelbrock 14" round air cleaner.

20231230_152954 by Scott Weckerly, on Flickr

[Yeller]

Supposedly facing back is the correct way to draw air out of the engine bay. However aerodynamics are tricky, all depends on where the low and high pressure areas are. Anyone got a wind tunnel we can play with?