Absolute minimum head/deck height?

[Jean]

I have an extra 91 casting b35 head thinking about it getting it machined, but need to confirm what's the maximum it can be machined before valves hitting pistons?

It's warped a little more than usual so if I have it machined I want to know what the limits are.

Basically let's say running 91 octane of course, how much can the head be shaved before it's going to be a problem?

Thanks!

[LowR3V'in]

Bentley says minimum permissible height is
126.6mm (5.063in.)

New the head is
129.0mm (5.0729).

It also says bmw does not give warpe specs on the m20/m30,
but for the m50, if the head is warped more then 0.3 (0.012in)
it needs replacing.

[Jean]

Right, but I've heard people shave them even more?

[LowR3V'in]

http://www.mye28.com/viewtopic.php?t=61584&highlight=shaved+head

Sorry if you've already looked at this, but in that thread, Paul Burke (m30 head god)
explain the b34.

On a 92mm bore x 86mm stroke engine it takes a little over 8cc to increase compression ratio one point, this equates to approx. .046 off the head (M30B34), this assumes the head has never been surfaced. Cam position can be restored with adjustable or slotted cam sprocket.

Piston to valve clearance may become a problem.

Paul

Perhaps contact him and ask. Will you be able to feel the slight raised compression?
You'll need to buy an adjustable cam gear to get it back into spec.

My block was decked 0.010" and my b35 head was surfaced 0.011." I installed a stock thickness headgasket and degreed the cam using both the intake centerline and 0.050" lift methods and both showed exactly 2 degrees retarded.