Big Block Intake Gasket - Rectangular Ports

[Ken K.]

Does anyone know of a good intake gasket for a 1966 427/425hp? I need them to work with rectangular ports. Fel-Pro, Victory, GM (Part number(s) of the correct set would also help.)
What about openings in the middle of the aluminum intake, under the carb. area, should these be open or block off when the new gasket is installed? (Circled in red in the photo below.)
I think these openings let oil into the chamber area under the carb. Is that correct?
Thanks for the advice....

[William O.]

Re: Big Block Intake Gasket - Rectangular Ports

MR. Gasket.

http://www.mr-gasket.com

[William O.]

Re: Big Block Intake Gasket - Rectangular Ports

Mr.Gasket photo.

[Ken K.]

Re: What about these holes. - Rectangular Ports

The other question was about these holes circled in red in the photo. What are they for, and all the gaskets is seen for these manifolds seem to cover these openings up. It that correct or should these be left open when the gaskest are installed? Thanks

[John H.]

Re: What about these holes. - Rectangular Ports

Those are secondary exhaust crossover ports which heated another passage below the one that heated the plenum floor; the OEM gasket blocked them off.

[Mark #28455]

it's an insulating space

Instead of using a sheet metal pan to block oil from hitting the hot crossover passage, the 4 barrel aluminum BB intakes had a cast-in "double bottom" to the passage which insulated the bottom of the intake from the hot exhaust gasses. That's why the ends are blocked off by the gaskets. In addition, the heads had a similar configuration around the crossover port too.
Mark