I am curious about whether or not the heat cross-over in the intake manifold is needed?

Is it a necessity to make sure that the fuel vaporizes, or is it really useless once the car warms up?
What are the advantages to removing it?

I have a stock cast iron manifold on my 440.

 

Most people try to minimize this function, but the truth is that especially on fairly stock cars --that tend to be leaner running with original smog carburetors, you can exhibit poor drivability even on a 40*F day if it's humid enough to cause the start of carb icing.

On the other hand, if you have an aftermarket carb that's jetted a little "fat" and you tend to drive your oldie only in warmer weather, you probably can get along fine without it.

Originally there were several things that worked together --the heat passage under the manifold, the butterfly in one manifold which when cold and closed, forced hot exhaust through the passage, and the regulated "heated snorkel air" to the air filter.

If you don't believe in the refrigeration/ icing effect of a carb, find yourself an engine with an unheated manifold, like a 6 with an aftermarket intak and headers, and no carb heat, or a Corvair or VW powered buggy with an aftermarket manifold.

You can sit there on a hot, humid day, rev the engine a few times, and generate cold water/ snow and ice on the bottom of the intake!!

 

Well, I need to cool the carb. I am adding an insulator gasket to hopefully solve the problem.

But if I can do without the heat crossover, why keep it? If anything, it just robs power from the engine since it heats up the fuel.

 

On my bone stock, original, Fury with a 383, it has a piece of foil backed insulation in the valley, underneath the intake. It can be seen at the rear of the intake manifold. It looks like it doesn't belong and I thought that someone added this at some point in the 41yrs before I bought it.

I recently purchased an original '68 4bbl manifold and AVS carb, along with some HP C-body exhaust manifolds that were on an original complete engine. When we took the intake manifold off.... there was a piece of foil backed insulation attached to the bottom of the 4bbl intake manifold!

This looks like it may be the factory's way of doing what you are trying to do. Rick

 

Just a quick update:

Used the felpro intake gasket that had the heat cross-overs already blocked. Initial start up is very rough, but after a few seconds, evens out. Basically, this gave me cooler air going into the engine, which is only positive.

 

I actually had carb icing. '70 Buick GS, Ram Air, 350. On a cool, but humid day, the car started and ran fine for about two miles. Then sputtered and stalled. Took the air cleaner off and found the carb WHITE with frost! Of course the exhaust heater hose to the air cleaner was gone cause of the headers!

 

That was a possible concern for me on a cool humid day. When I first did this, it was in the 90's with high humidity, and the carb. was actually freezing cold even after the motor was running for a few minutes.
But once you get past this, the benefits out-weigh that.