M20 head machining

[E-Thirty]

So after putting the cylinder head I purchased on this forums on, I noticed foamy oil on the dipstick and oil running from the side of the head gasket. I followed all the procedures in the bently manual(torquing sequence and specs), so I'm assuming the mating surface being the culprit.

So before taking it to the shop, I'd like to ask how much material would have to be taken off before an adjustable cam sprocket is recommended?

[nando]

have you had it pressure tested? it could be cracked..

[E-Thirty]

I'm going to have all that done at the shop. Just like to know when I would need an adjustable sprocket.

[E-Thirty]

Anybody on here had their m20 head machined without messing with the cam timing?

[whiltebeitel]

4.909" is minimum thickness, gasket surface to gasket surface, ~4.925" is all I could find without my Bentley handy. This may or may not be reliable info.

An alternative from http://www.rebuiltautoengines.com/bmw-articles.html

REVISED CYL HEAD MOUNTING COMPONENTS & PROC
Revised Cylinder Head Mounting Components and Procedures on
BMW 1983-86 325e and 528e (VIN M20B25 and M20B27) Engines

AERA has received many calls on leaks of the cylinder head to block joint and cylinder head bolt breakage on BMW M20 series engines (applicable to all displacements). The following revised components and procedures should eliminate these difficulties for AERA members and their customers.

A revised cylinder head gasket with improved sealing should eliminate oil seepage between cylinders No. 3 and 4 on the exhaust side of the engine. A .012 (.3mm) thicker head gasket should be used when cylinder block deck height or cylinder head minimum thickness specifications are exceeded.

Previous Head Gasket 11 12 1 278 305
Standard Head Gasket 11 12 1 708 891
Oversize Head Gasket 11 12 1 713 493

Revised cylinder head bolts of increased strength and hardness along with a new torque procedure should further reduce head gasket problems. The revised cylinder head bolts are easily identified by their Torx heads and black finish. BMW recommends installation of the revised bolt whenever the cylinder
head is serviced. Bolts should be replaced as a complete set available under the Part #11 12 1 726 478 (14 bolts).

Use the following torque procedure on the revised bolts:

1) Torque all bolts to 22 lbs.ft. (30 Nm)
2) Turn all bolts 90*
3) Turn all bolts an additional 90*

The waiting and running time requirements used with previous procedures no longer apply.
The AERA Technical Committee

[E-Thirty]

Interesting. Thanks for that info!