Whats the original M54 Cylinder head Thickness?

[megadrive]

hey y'all

Im have blown exaust valve and am currently replacing it. However, I wanted to find out what is the orginal cylinder head thickness is before I decide whether to resurface it or not because I suspect it has been resurfaced before by the previous owners and if that is the case I would have to use a thicker gasket since it would be the second resurfacing if not the 3rd. The heads can only be resurfaced a number if times and thicker gasket need to be put in to compensate the lost surface if it is too much. So does anyone have the specs for the orginal head thickness as I cannot find it?

I measured my head flatness warpage, it is currently 0.15mm(0.006inch) Is that within the acceptable tollerance?

Thank You!

[andrewwynn]

https://www.engine-specs.net/bmw/m54b30.html

[andrewwynn]

Buried in the wealth of information:?140.0 standard head height

i found notes to the effect of 6 mil being the max allowed and another that said BMW is against milling the head flat (yet they make thicker gaskets for when you do).

[Effduration]

I don't have the factory head thickness. But AW's data seems plausible. We have tried to measure the thickness of just the mating surface of an M54 cylinder head but there is not a smooth, recessed surface on the combustion side of the head from which to take a measurement, which could be compared to several other cylinder heads which have never been milled. All of the recessed surfaces are rough, casting surfaces, which are not good surfaces to measure from.

I have sent 15 M54 cylinder heads to my machinist and he looks and determines how many thousandths of an inch he will need to remove to deck it, and WHETHER that measurement will cut too close to the valve seats.

The two stock M54 head gasket thicknesses are 0.70mm(factory) and 1.00mm(after resurfacing). By inference, BMW thinks you can take, as a maximum, the difference of 0.30mm (approximately 12 thousandths of an inch) off of a cylinder. head.

i have discarded 4+ cylinders heads because they needed more than 12 thousandths removed, or had been previously milled too much, etc. I have also 3 times had a cylinder head "baked" in an oven by a machinist to remove most of the warp before machining. That process was too expensive...about $800 per head

[andrewwynn]

The baking solution was what was recommended for the S54 vs. resutface. If you're not racing the car I would have no problem taking off that 0.3mm to match the thicker gasket.

If it was within 1 mil of spec flatness I'd probably "just send it".

A 10mm 10.9 bolt yields at about 9000# so about 125,000# holding the head down will definitely remove some of that non flat. Just a thought.

[andrewwynn]

If you wanted to compare and had one you can measure cylinder depth maybe more accurately. I have no idea where they would take that 14.0 cm thickness measurement