Heat crossover

[Paul]

Cliff, the new intake gasket set I have has 2  thin pieces of metal to block off the exaust heat crossovers from the heads to the intake. Is there any real advantage to using these? I read somewhere that heat soak will eventually heat up the intake and carb so theres no point in using them. Any thoughts?

[Cliff Ruggles]

I do NOT recomend blocking off the heat crossovers for street engines.  It takes too long for the intake to heat up, wasting fuel, etc.  You can also get "icing" in cold weather.

In addition, any divorced or hot air style choke will not work with the heat crossovers blocked off.....Cliff

[Schurkey]

...keeping in mind that "blocked off completely" is different from "suitably restricted".

There were many OEM Chevrolet applications where one side (sometimes both sides) of the intake manifold had a sheet steel restrictor installed in the gasket.  The restrictor plate had a ~1/2" hole in it that allowed SOME exhaust flow.  Wouldn't surprise me to discover other makes had a similar arrangement.

The side that got the restrictor depended on which side of the engine had the heat riser (EFE) valve.  I don't remember if it went in the same side as the EFE, or the opposite side.  (Probably the opposite side.)

[qjetsrule]

I AGREE WITH CLIFF AND PAUL, BUT ON A CAST IRON INTAKE I WOULD USE THE FULL CROSSOVER OPENING, ON AN ALUMINUM INTAKE I WOULD USE A RESTRICTED CROSSOVER OPENING DUE TO THE INCREASED HEAT TRANSFER WITH ALUMINUM. GOOD POST