Chevrolet Repair: Chevy - Carb Problem, port fuel injection, flapper valve

Question
Have an 86 El Camino  305 engine/w/4 barral Q-Jet. When temp exceeds 100 degrees (outside) car
runs very rough/hard or won't start. Runs w/ a
severe lack of power. My mechanic says the carb
should be replaced. States gas is boiling in the bowl. He's given me a range of options..from re-
building present carb to multiple port fuel injection.  I'd like to know what is the best option. States the primary objective is the need to lessen the heat in engine compartment..even suggesting a cowl induction..pls advise..

Answer
Hi Mik,
When that car was brand new, it ran fine in 100 degree ambient temperature.
I think I would work on what is making it run so hot under the hood.
Airflow AND coolant flow through the radiator are a must. Those tubes get restricted with mineral deposits inside.

And check the fan clutch for proper operation. If it tends to heat up worse in town, but cool down on the open highway, you may need a new one, or even a flex blade.

Then make sure there are no restrictions in the exhaust system, like a plugged muffler or Cat..
Another item on the exhaust system is the manifold heat riser valve. One of the exhaust manifolds has a vacuum operated flapper valve that closes by vacuum when the engine is cold, forcing the exhaust from that side to pass through a port in the intake manifold, directly under the carburetor, and exit out the other side. This was called EFE, for early fuel evaporation, and helped the cold engine run better by warmung up the floor of the intake manifold. (Isn't that just what you don't need?)
I have seen the vacuum controller for that type system stick, causing that valve in the exhaust to stay shut. That makes the engine run quite warm, and real hot under load.
It is also possible for the valve itself to stick.

Remove any BUG screens, or air restricting grilles from in front of the radiator, because you need all the air you can get to pass through there, and carry the heat away.

Proper tune up and ignition timing are necessary, but I immagine you have already checked that.

And Last...if you have an automatic transmission, and it is slipping any, it will dump a lot of heat into the radiator mounted transmission cooler, compounding your problem.

Good luck,
Van