preventing fuel from boiling in the carb

[F-BIRD'88]

Which carb on which intake manifold?

[modok]

A lot of times the problem is the carburetor floods because the fuel lines and fuel pump got too hot.

In many OLD fuel pumps, there is no way for excessive pressure to RETURN to the fuel tank, so it overpowers the float instead.

You could probably observe it happening with a good fuel pressure gauge.

[Belgian1979]

Holley 650 DP

[F-BIRD'88]

A wood carb spacer (Edelbrock or home made) helps a lot.
Along with the 2 ply with lil air gap Holley carb heat shield that extends out to under the carb bowls.

+Seals IT fuel pump mounting heat isolation gasket.
If hot soak re starting. First crank it over with the ignition power off.. 1-2-3-4 then hit the spark. This purges out the over rich fuel mix, (that won't fire) drawing in new air fuel to fire easy. When it fires up hold throttle at 2000+- rpm to use up the too hot fuel in the bowls. Lets in new cooler fuel.
Avoids first throttle hot stumble.
The ethanol in modern gasoline aggravates this on carbed motors in the summer. This is how you "clear it" if when its "hot soaked"...

The 2ply part of the Holley carb base heat shield can be riveted with a air gap or a layer of thick paper between the sheet metal layers. You can buy it or make your own..
GM Vettes and Camaros had this carb heat shield.
Paint it white both sides . Holley #108-70 or make your own.
Paper (layers) is great for heat isolation.

[F-BIRD'88]

Back in the carburetor era the volitility of the gasoline was adjusted a few times a year ."summer gas, winter gas"
To aid cold start and summer heat soak vapour lock resistance on carbed engines.

With most all cars being EFI now, the big gasoline supplyers don't bother.

[F-BIRD'88]

The short rubber fuel hose that connects the fuel pump inlet to the frame mounted fuel feed hard line must be of proper type or it will collapse kink shut if when hot.

A rear mounted (rubber noise vibrationisolation mounted)(near tank) Carter P4070 electric fuel pump is just right as a "pusher pump". This pressurizes the feed side of the fuel line to the mechanical pump. You only need turn it on when needed. (hot soak, drag racing )

On the Holley fuel line splitter block near the carb there is a extra small fitting. Everybody mounts a lil fuel pressure gauge there. Thats not what its for. its for a fuel return line back to the fuel tank. Restrict to .030" orrifice. be sure the
return line goes down under the in tank fuel level so as to not airiate the fuel in the tank as it recycles.

[F-BIRD'88]

You will notice that modern cars with electric cooling fan that the fan runs after shut off to blow out the hot under hood air as well as force cool the radiator on hot shut down.

on cars with mechanical engine cooling fan some carbed cars had a small 12v ducted fan that blows cool air at the carb base. , after shutdown.
A common 12v dc PC computer cooling fan works for this. Should be on a automatic timer or thermostat switch.. Cools the hot soaked carb.
Carbed 305 third gen F body cars had this as add on service item. to cure "hot soak" QJet carb.

[rp930]

I’ve also had success with this. Especially on factory BBC where the fuel line runs behind the water pump and you want to keep the factory look.

Design Engineering 010671 Vapor Block 3/8" I.D. x 36" Fuel Line Sleeve https://www.amazon.com/dp/B07QPZTBXV/re ... nFbR17RP6F