Vortec heads / intake bolt patterns

[workingr]

I have a set of Vortec heads (Patriots) , and they are drilled/tapped for either standard or Vortec style intake manifolds.

Am I better off using the traditional 6 hole intake, or the 4 hole vortec style intake?

After I decide which intake, should I put set screws w/loctite in the unused holes, or just leave them be?

To me, it would make sense to use the 6 hole pattern, vice the 4, but then I ask myself, why would GM go to a 4 bolt pattern.

Rob

 

[Damon]

You need a Vortec-style (4-bolt) intake. It's not so much the bolt pattern that makes the big difference- it's the fact that Vortec-style heads have the roof of the intake port considerably higher than older 6-bolt style heads. Not only will it cause a wicked port mismatch, it might not even seal up against an old 6-bolt intake.

You don't need anythign on the unused bolt holes- they are almost certainly "blind" bolt holes that are not open to anything on the back side. Even if they are, the Vortec gaskets will probably block them off (like on the center 2 bolts that might be open to the lifter valley on the back side- the gasketys will seal them off).

You probably want to know WHY they would dual-pattern the heads like that if they only match up properly with a Vortec-style intake. RACING is the reason- modified intakes than you can't buy off the shelf. Easier to modify the ports on an intake than change it's bolt pattern.