TA Intake Manifold 340-6

Does anyone know why they list a different Part # in the Mopar parts Book for a 1970 340-4 and a 1970 340-6 intake gasket.
Is it the port size or just because it's an aluminum manifold ?
Bob

iirc one is composite and one metal...

Ok, so I think the TA 340-6 gets composite because it's aluminum
Thanks Bob

Aluminum notoriously has flatness and porosity problems... fiber-faced always is the better choice to give allowance for flatness and seal porosity issues.

ALSO... most people are unaware of the core-shift in the ports of the six-pack manifolds. An embossed steel gasket may, depending on the core shift of the ports -- as cast and finished from the factory -- allow the raised embossing to fall inside an intake port, in particular at the valley area, but anywhere possible... and then have sealing vacuum problems at that area. I've witnessed this problem on several six-pack manifolds ... especially the factory original manifolds... but same can be present on the MOPAR-Edelbrock aftermarket castings.

So... best to use the fiber-faced gaskets... (example being the Fel-Pro MS 90109 gaskets (fiber faced... but with embossing)... or better yet... their PERFORMANCE RACE gaskets (and trim open the center exhaust cross-over ports if you desire).

I'm a former Fel-Pro engineer from their aftermarket division... I know the history very specifically on this subject.

Thank you very much for this info
Bob

Like the post says above hard to get much better, so I use the good Fel-Pro on the heads 1008 and intake these on the intake