2007 S40 Having head machined...how much??

[Craigd2599]

Fellas,
I am doing a head gasket change after overheating. Took the head to a really great machine shop here in Lynchburg. The machinist asked me a question that I was wondering myself. With this being an interference motor and the tolerances being close to begin with, is there a maximum that is recommended he take off when planing the head? (Assuming it's warped) If so, is there a head gasket for use on a head that has been milled? Is it possible to bottom the head bolts because the head was decked? Anyone know this sort of thing?

[Sanatarium]

Well, the first thing the machinist should check for is whether or not warpage is present. From my experience, sometimes warpage can be so slight that machining isn't even needed. Assuming there is 0.005" of warpage, meaning, the highest point is 0.005" higher than the lowest point on the head surface, it is only necessary to remove 0.005" for the head to be perfectly flat. However, if the OEM spec says that +-0.002" is acceptable, then maybe only 0.003" of material needs to be removed. Long story short, the machinist should know these things, and will recommend the best course of action. You may even be able to get by with heating the head to 400 degrees on top of some strategically placed shims, and letting it age at that temperature to un-warp the head. This will be determined by the straightness of the camshaft bores. If the bores are not straight and parallel, then machining the head won't do you any good.

I do not know about your other questions, hope this helps.

[Craigd2599]

It does...thank you!

[Craigd2599]

So I got the head off and it was straight. The head gasket had no visible blowout and that I could tell, the bolts were not stretched. But I had water in cylinders 2/3. i cleaned it up and reinstalled and I am hopefully finishing it today. We shall see