As I have previously posted, I purchased a rebuilt cylinder head from Cylinder Heads International (CHI) in Grand Prairie, Texas. I know I took a chance, and I think there is a problem, but I haven't installed it yet and I will return it if necessary!!

My understanding from CHI is that the head has been pressure tested, magnafluxed etc....and that a valve job has been performed to MBZ specs. I called for more info. and the guy who works on the MBZ heads said that valves are not new, they are used valves that have been reground. Also, new guides, seals and springs were installed. I asked about angles of grinding, and he said that "a three angle valve job" was performed.

Anyway, here is the problem: I have the full set of MBZ shop manuals. In the section on machining valve seats (05-291), it gives the proper specs. for reground seats and new valves. One dimension that I checked was the recess distance of the valve flat surface from the mating surface of the head. I measured using a metal straight edge ruler layed on edge on the mating surface of the head, and measuring recess of the valves using metric feeler guages.

The MBZ manual says that the MAXIMUM distance for both exhaust and intake valves is 1 mm. On the head I recieved, the intake valves are recessed 0.7 mm below the mating surface of the head (within spec), whereas the exhaust valves are recessed 1.2-1.3 mm from the mating surface of the head!!! This is .2-.3 mm greater than the 1.0 mm specified in the MBZ manual.

Should I return the head?? Note that the MBZ specs. are for NEW valves and reground seats. The valves in mine are not new...they were reground...is this therefore OK?? Is it common to just regrind old valves, or should a "valve job" always involve new valves.

I dont really know what I'm doing, but I want to come up to speed before I call them.

I also removed retaining nuts and springs to feel play in guides (I didnt pull threaded portion of valve stem into seal). There is absolutely no play (wobble) within the valve guide. Valve stem seals are obviously new, and rotocaps rotate freely.

Any advice will be greatly appreciated.

Thanks,


Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)