Intake Manifold Heat

[Ray C.]

Hi!
I replaced the intake manifold gaskets and I installed the heat restrictor plates for the carburetor passage earlier this year. The paint on 250 HP cast iron intake has burned off in this area. Is it a good practice to use these restrictors?

Thanks! Ray

[Clem Z.]

blocking the heat riser crossover at the cylinder

heads is not a good idea because with a cast iron intake manifold it does not conduct enought engine heat to the carb like the aluminum manifold does for good drivablity. plugging the 2 holes under the carb on a cast iron intake will cause no problems and is beneficial

[Christopher R.]

Re: blocking the heat riser crossover at the cylin

Clem, can you restate your comments. I don't understand. Do you recommend blocking the crossover on an aluminum or an iron intake?

[John H.]

Re: blocking the heat riser crossover at the cylin

If you block off the crossover passages on a '66 or later, your choke won't work either; it depends on heat in the thermo coil well in the manifold to open the choke. The crossover passage is there to quickly heat the floor of the intake plenum to improve atomization of the air-fuel mixture in cold weather and prevent raw fuel from "wetting-out" on the walls of the cold manifold until engine heat warms up the manifold casting, and it takes a LONG time for an iron intake to warm up just from transferred engine heat. May not be a big deal in Florida or California, but it's important up here in cold weather.

[Clem Z.]

Re: blocking the heat riser crossover at the cylin

you can block the heat riser cross over at the cylinder heads with a aluminum intake manifold BUT do NOT do it with a cast iron intake manifold.