Hey all

I am looking at a project down the road and had a question on the Vortec heads.

I am aware that the holes to mount the manifold are straight up and down on the Vortec heads and are angled on non vortecs.

However, I was hoping to use the Offenhauser cross ram intake

Can the holes be filled and re-drilled at the correct angle?

 

Typically the heads are redrilled to accept the 90 degree bolt pattern of earlier manifolds.

The only question is whether the ports can be made to line up. The Vortec ports are raised relative to the older pattern. The mismatch may be enough to keep the older manifold from even working, or enough to make it ineffective.

A manifold designed for Vortec heads is the best bet, assuming you're going for something more than looks.

 

9 times out of 10, mabye even more out of ten, the intake ports don't line up correctly. Not enough so that it warrants the cost of a Vortec-specific intake.

 

You could make a custom Vortec Cross ram manifold by starting with the lower Intake manifold from a factory 96+ vortec truck motor. The lower manifld base is very simular to a lower base of a Cross ram intake. Would require fabricating a manifold top/carb mounting cover and modifying the plenum but could be done.
here is a pic of the lower vortec EFI manifold.