Q&A / Tech

Mailbag: Mating and Sealing Tips for Milled Cylinder Heads

Q: I have a Chevy 350 small block. The heads have been milled .020-inch; the block and Weiand Stealth intake were not cut. Will I need a thicker intake gasket to mate the Stealth to the heads properly? Will I need to mill the intake, and if so, by how much? The Stealth is like-new and I don’t want to mess it up just for this engine. If there is a gasket that will work with this combo, that would solve my problem.

A: Depending on how much material is removed from your cylinder heads, you may need to cut or trim your intake manifold. Just recently we did a post on milling that covered this relationship between milled heads and the amount of material that needs to be removed from ther intake or block. You can review that Milling 101 post here.

The good news is a .20-inch mill job should not require cutting or trimming the intake manifold. Fel-Pro makes a 1/16-inch thick gasket that should do the job nicely. Just to be sure, you can do a dry fitment with the gaskets. Make sure the head and intake mating surfaces are clean, then lay the gaskets down without sealant or gasket cement. Don’t put in the end rail seals or gaskets. Lower the intake, then start the intake bolts to check for bolt hole alignment. If everything checks out, lift the manifold back off, put silicone sealer on the corners and end rails on the block, then carefully lower the manifold back into place. Torque the bolts down following the correct torque sequence. Maximum torque with an aluminum intake is 24-25 ft.-lbs.

This is another in a series of weekly Q&A Mailbag sessions with Summit Racing‘s tech department, in which there are hundreds more. Click here to see them all

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