my manifold flange and turbo flange are warped. i can get a .3 mm feeler gauge under a straight edge on both surfaces
should i get a thicker gasket of have the surfaces machined?
will machining lead to the surfaces warping easier?

 

If you are getting manifold distortion, you most likely have external loading that you need to take care of. Without looking at your setup, make sure it is not overconstrained and can grow as it heats up.

I would have it machined to get it flat again. As long as you don't take off too much, it won't adversely affect the manifold and turbo.

Kevin

 

Some shops have a flat table sander that will clean up the flanges very easy!

 

Yup, get em decked.

 

Machine shop usually charges around $40 to resurface my manifolds. A thicker gasket may not help...what type of material gasket were you using? I'm planning on getting a graphite one. The big thing is to make sure you tighten the bolts/nuts down slowly in a criss cross pattern...that worked for my buddies KA-T 240sx.

 

copper gasket