964 valve guide wear question

[jackoporsche]

I am in the middle of resealing the engine for my '90 C2 964. I have completely disassembled and inspected the all original 62,000 mile 3.6L. I have noticed some wear in the exhaust valve guides and am wondering whether I should have some head work done while it is apart. With the valves 10mm off their seats, they move side-to-side 1mm measured at the valve face.

The plugs have no signs of deposit, and the car ran fine prior. It leaked so much oil though, that I can't say how much it is actually using!

I was hoping to just replace the seals and move on. Should I stop and have the guides replaced? How much wear is acceptable?

[unclebilly]

964 valve guides are notorious for premature wear. Get them done.

[cgarr]

You will notice more wear in one direction. How do the seats look?

[jackoporsche]

The seats and contact areas on the valves look good - not beat up or pitted. The valve margin is not clearly defined, though, as it is on the intakes.

[Eagledriver]

That's quite abit of wear. You really should do them while you have the engine apart. It will run that way for a while but then you will be taking the motor apart or risking a dropped valve.

-Andy

[jackoporsche]

Okay guys, I knew this was kind of a no-brainer to get the heads done. Just wanted to get some opinions because I know there are a lot of 911s running around that run decent on wasted valve guides. I guess I wanted someone to say run it, they're all like that! I called local machine shops and Porsche specialty shops. I shipped the heads to Ollie's this morning. They will do the valve job AND mill the heads to accept steel shim head gaskets as I have the early barrels with no upper seal groove. I'll be back on track in a couple weeks.

[930gt-40r]

I have had good experiences with Verdan machine- they do a very nice job.
964-993 eat up their exhaust guides partly because of the sheild on the bottom of the motor holding the heat in the lower engine area

[jackoporsche]

Got the heads back from Ollie's with the valve job, new exhaust guides, and combustion chambers machined for steel shim head gaskets they supplied along with the Porsche part number. Ike at Ollie's was helpful and friendly. So far, so good. I'll let you know how it runs, and hopefully doesn't leak!!!

[dick911]

Hey Jackoporsche,

As I understand from your story about the machining job at Ollie's you will use the original non-gasket cylinder barrels and Ollie will machine the heads in a way that the later type head gasket will fit ??

Can you take a picture on one of these heads and post it for me on this Forum ?

Anyone out there who has good (and above all reliable..) experience with this solution ? (instead of buying newer type of cylinder barrels which will house the gasket...)

Many thanks in advance for ypur reply.

Dick911

[jackoporsche]

Dick911,

Unfortunately I did not photograph the combustion chamber area of the heads before reassembly. Ollie's machined the area of the heads that contacts the tops of the barrels down to allow the installation of a flat steel shim gasket ring (Porsche part #930 104 381 01) between the head and cylinder barrel. This allows the cylinder and barrel to expand and contract on an uncommon surface cutting the movement 50% on each surface. Much like modern multi-layer steel shim gaskets used in most current engine designs. Also, there is a gate created by the shim that will stop the small amount of dormant oil lying on the lower sides of the cylinders from flowing against the head in a parked engine.

Will it work? Mine's not back on the road yet, but Ike at Olllie's tells me they have had success with this repair as they did many more this way before Porsche released the redesigned barrels. This approach made sense to me as my 3.6 has low miles and really wasn't leaking much at the cylinder head to barrel seam.

[dick911]

Very interesting !

I hope others have experience with this solution and will share the long term experiences with us on this Forum.

To me it seems a logical and reliable solution.

Dick911

[jackoporsche]

Hey Dick911!

I actually did take a photo of the modified cylinder head. I just didn't remember shooting it I guess. Here it is:

[dick911]

Thanks !!

I hope someone will post his long post experience with this solution.

Regards,

dick911

[jackoporsche]

I finished up my engine project in July and have about 1,000 miles on one leak-free, great running engine. Thanks to all for their suggestions and to Ollie's for some nice machine work!