One More Q: Lap Valves With New Guides Installed?
 

And another valve-lapping question: should I do this with new guides installed? I've already installed one new guide, and have lapped that valve with this new guide in place.

My sense is that the guide will help insure that the valve seats properly while lapping, but my two concerns are that the valve guide is not designed for this type of (lapping) motion, nor is it designed to have the valve itself repeatedly removed and reinstalled a few times, as is necessary for this lapping process. Another concern is that lapping compound grit may find its way into the new guide, where it could be difficult to clean out.

Any opinions about installing new guides prior to lapping? Thanks!

You should be fine. Just use only as much compound as is needed (to get the seat wet), and rinse thoroughly afterwards.

Did you ream out the new valve guide??? The Porsche manual says it must be done. I'd be tnterested to see if other DIY guys have done or not done it and how it turned out.

I'd meant to say valve Seals - not guides. I'd installed a new seal in my first valve prior to lapping, and now I'm not sure this was a great idea. The guides seem to be within spec, and probably give enough extra alignment help while lapping...without the seals in place. So I think I'll do whatever remaining lapping is necessary without the seals in place.

Yeah, I'd do it without the seals in place.

Ditto...you wouldn't want to get compound on the seal.

Yeah, do not install the seals until the head is ready to be assembled. Clean the ports, valve seats, and guides thoroughly first. That grit will tear stuff up very quickly on startup if any is left behind. Be very careful not to get any on the stem or in the guide since the guides are soft bronze(?) and scratch/wear very easily. Make sure you use good assembly lube on reassembly.