Head milled - stock or thicker/MLS gasket?

[ChipM]

I had a slightly warped head milled 0.012". Shop that did it was under the impression that BMW made an oversize gasket, but apparently that's not the case.

It appears that I have the choice of a stock head gasket, or a +0.012" multi-layer steel gasket. The MLS gasket requires a very smooth finish, and I have not touched the block.

What is the best solution here? Any downside to the stock gasket/higher compression? Can the MLS gasket be installed without milling the block? Is there a way to refinish/smooth the block in the car?

Thanks for the input.

[pbonsalb]

012 is a lot. Normal might be 002 to 005 To get back to stock CR, use an 080 MLS gasket. I also believe I have seen an OEM gasket for just this sort of situation, but am not sure how much thicker than stock (070) it is. Might be cheaper than the MLS that VAC sells. I think the VAC one is Cometic, so there might be online sources that are a little cheaper.

Copper spray it and don't worry about the surfacing. I have one in my supercharged M3 and did nothing to the block surface (head was resurfaced).

Higher CR is probably fine, but 012 is a lot and you could be as much as 1/2 point higher. You might want to calculate that. I took off 004 and used an 080 gasket instead of the stock 070 and calculated my CR decrease at about 1/10 of a point. Also, your cam timing could be a little off -- not sure how you would calculate that. Might not be enough to worry about.

Philip Bradley

[Casebrius]

obviously clean the hell out of your block to get the old crap off. You shouldn't need to resurface it though. I used some cleaner/degreaser spray and a green fibrous dish scrubber (not metal like brillo) and mine was fine. I had ~.010 milled from my head and used a stock gasket. Your way better off buying the whole gasket set - it has EVERY gasket you will need for a head job. Mine runs like a champ, I'm not sure how much it actually increased compression, but it had to a bit.

[ChipM]

obviously clean the hell out of your block to get the old crap off. You shouldn't need to resurface it though. I used some cleaner/degreaser spray and a green fibrous dish scrubber (not metal like brillo) and mine was fine. I had ~.010 milled from my head and used a stock gasket. Your way better off buying the whole gasket set - it has EVERY gasket you will need for a head job. Mine runs like a champ, I'm not sure how much it actually increased compression, but it had to a bit.

Hmm, so you went with a stock gasket at 0.01? BOth the Bently and the Haynes say that 0.012 is the cutoff for going with a thicker gasket; I'm (according to the machine shop) right at that. I'm debating going with a stock gasket just because of concerns with an MLS on the raw block.

So, you're not having any issues from higher CR or anything?