[David Brown]

I am about ready to install 56X heads on my 1970 455. I know I need to fill the hole in the head that results in using 72 and up heads on a pre72 intake.

Do I need to fill both heads or just the right side? This has been discussed before, but I can't find the tread.

I don't want to eliminate the crossover, just eliminate the leak that will occur with the 6X on my earlier intake.

[Kenth]

Drivers side is fine, passenger side needs attention.

[David Brown]

That is what I thought. Thanks

[ken66]

Can this be solved with a Felpro 1233 gasket?

[Skip Fix]

You know I always wondered why the factory made the intake that large only just one side with the head holes being smaller. Maybe for the choke heat? Seems it would still get just as hot with conduction and a small hole.

[johnta1]

Can this be solved with a Felpro 1233 gasket?

Is it a blocked gasket?


Exhaust Cross Over

[David Brown]

Is it possible they made one size smaller to aid in the gas flow? Large when the gas is hottest, smaller as it cools, like some exhaust systems with larger at the manifold and smaller at the end of the exhaust. When I bought my long branch manifolds, I was told that larger pipes at the manifolds and smaller after the mufflers kept the pressure closer to equal as the exhaust gas cooled. Not sure how much that would effect the crossover though.

[sts]

the 1233 does everthing

small to small
large to small
small to large
total bock

https://www.google.com/search?q=pict...w=1344&bih=716

[MescaBug]

Thats a 1233. Comes with an assortment of blockoff plates (not on the picture). You can block the entire crossover including the 'airgap' over it, or leave the crossover open and block the deadspace only.

I've been using the 1233 kit for some time, works like a charm. The blockoff plates on my 455 are holding on after 3000miles.

The only downside is that you have to cut the passenger side gasket to clear the water nipple on the head. No big deal.

[Joel Koontz]

Back when I was running 6X Heads with my 66 Tri-Power Intake, I modified the intake to seal this area.

I simply welded up the top of the passenger side port and reshaped it to approx. the same shape as the drivers side port.

It sealed up great, and with the intake installed, you cannot tell it has been modified.

[Zimtok]

I've always used the 1233 kit that MescaBug pictured above.
As he said I never had any problems.

I am currently using the 1233 kit on my 1965 421 with 1975 heads and a 1966 Tri-Power.
Using the insert with the small opening blocking off the upper port there is no leakage/problems.



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