ok i have a question I have a 74 400 with 16 heads (from 1968)on it .. so im reading the other day and i find out that intake manifolds from 1970 foward will not fit on these heads ? i have a edelbrock rpm is this ok ? i checked edelbrock they say they fit from 1965 -1979 so how can edelbrock fit but not a factory manifold ? thanks

Aftermarket manifolds have big ports that fit many year's heads. You only have a problem when mixing and matching factory intake manifolds.

Actually, it's the crossover ports that are small on the aftermarket manifolds.

The early (1967-1971) factory manifold has the large crossover port that causes the problems with the later heads.

The early heads have the large crossover ports that leak with a later manifold.

The aftermarket manifolds use large flanges and small ports to solve the crossover port mismatch.

thanks guys

No problem. Always willing to provide incorrect information!