M50 M52 S52 Cylinder Head rebuild info, specs, differences

[Wojtek79]

I am hoping to someday rebuild an M52 engine that will drop into my E30. I've partially rebuilt an M20, but those are not that hard. The 24v engine is similar in design, but it has it's own quirks so here I am hoping to learn them.

I was talking to a friend of mine about the M50 and M52 heads. Apparently as long as the cast is the 400 number, the only difference between the two heads is that the heads on the M50 motors have two temperature sensors, while the heads on the M52 have both sensors combined into one. Anyone have any input of this?

I was also looking onto machining specs for both heads. I own a Z3 Bentley manual which only covers OBDII motors so I have no M50 info to confirm. The manual states the following:
http://www.z367.com/z3/bmfr/M52headspec.jpg
Measured this way:
http://www.z367.com/z3/bmfr/M52headpic.jpg

Is it safe to assume that the M50 head would have the same machining specs as the M52 head?

Any tips on rebuilding these heads from those who have done it before??

Can the cam trays with be moved from one M50 head to another?

Is the 3 angle valve grind all that necessary for a stock engine, or is a regular valve grind using the local autoparts store valve grinding compound adequate?

Does anyone know how many cast variations exist for this head? I know that on the M50 there is the Vanos cast which is the 400 cast, and there is also the early non-vanos cast. What else is out there?

Also, what do you guys think about the fact that it states no to machine the S52 head? I though the S52 head cast is the same as an M52 cast. It's the cams that make the difference. I am assuming higher compression on the S52 motor has something to do with that?

[SWISS]

An un machined M50TU head is slightly thicker than an S52 head. I had one shaved 5.546 was the final depth on it. And yes, all my S52 internals went over into the M50 head and I even got a spot for the E30 temp sensor now. :alright

[Wojtek79]

The one I have now is at 5.510 after machining and without the correct specs I am not sure if it is acceptable.

Someone out there has to have an older bentley manual or a haynes

[SWISS]

That is fine just be sure to go MLS and ARP while you have the chance and spray the MLS with copper sealer.

[orangehatter]

Definitely go with ARP head studs over using factory stretch head bolts. Much easier assembly and a bullet proof design.

[Wojtek79]

Found my info. 5.500 is the minimum on both.

[Wojtek79]

Ok. I have another one. Does anyone know the difference between the 400 cast and the 070 cast? They both look to be the same, and both have single vanos units.

[LeoStraight6]

Awesome thread guys, after doing a lot of playing around with various figures in an excel spreadsheet I have always been under the impression that the M50TU cylinder head had to have a very slightly larger combustion chamber as there was a 2cc difference that I could not work out.

All the M50/M52 engines share the same 1.75mm head gasket thickness and part numbers (so same bore as well) so with only changes in piston compression heights, my numbers were off by 2cc so it must be due to the increased head thickness in the M50TU which means larger combustion chamber :)

Would be absolutely awesome if someone had the new specs of an M50TU head.

[gerbercomplex]

I'm curious of the differences between the 070 and 400 heads myself. I have been working on a head swap, and just noticed that the 400 head I picked up to replace an 070 doesn't seem to have the coolant connector on the back like the original head had.

[imwhyteyo]

What about intake and exhaust port size, are they any different as well? Any being more efficient in flow vs. velocity? Curious of more desirable net gains. in finding a s52 head, what makes it better than an m50 beside the cam profile? Get nitty gritty on all details!

[Teddy Bomber]

http://www.z367.com/z3/bmfr/M52headspec.jpg


it's funny that they make a difference between S52 and M52 head when it comes to machining . . because the heads are no different . .

[etexis]

valve to piston clearance 3.2L vs 2.8L 2.5L

[Mandrew98]

Is that true?? Is it because of valve to piston clearance?? I have an m50 head that I'm going to put on my s52 block. Are we sure you can't machine the head?? This is the second m50 head I'm putting on, first one cracked, and when it was on my compression was only about 130... Also it seemed a little less powerful especially at lower rpm. Could be my imagination but I sure would like to shave this head. Also, is there a thicker head gasket to use and if so, how crucial is it that it be used. I mean, how much would I have to remove to justify a larger gasket?? It's not like there's alot to take off anyway. So I guess my question is has anyone taken a tiny bit off a 1738070 head, put it on an s52 with regular gasket and been OK??

[pbonsalb]

You can take off up to about .010. I would run premium gas. There are thicker MLS gaskets but I would just run an Elring.

[Mandrew98]

Great news!! I'm going for it!!