964 cam shims - 2 on each side??

[ChrisBennet]

A few years ago I rebuilt a 964 motor that had most likely been apart at some time. When I got into it I found that it has only 2 shims under each cam sprocket. I thought "hmm, maybe it's a 964 thing" but I measured it up like I always do and sure enough it was supposed to have the same number of shims as all the other 911 motors I've worked on (3 on on left side, 4 on right side).

(I used the specs from my 964 factory manual printed in 1992. Left spec 98.07mm, right spec 43.27mm. )

Fast forward to this week and my friend Eric is tearing down his 964 motor and what does he find? 2 shims on both sides. His motor has also been apart for the cylinder update at some point so it's possible the his shims were lost at some point also.

Is it just a weird coincidence that both these 964 motors are missing the same shims? Did I miss a memo? Is the factory manual wrong?

-Chris

[ischmitz]

Hm, I had MikeZ's top end of his 964 motor apart for a reseal and guess what - 2 shims on each side. FYI, its a 93. I don't remember for sure but believe mine (92) also had two on each side......

[ekessel]

To further the confusion. In the C4 manual I have from 1992, on page 15-2b, the item description for the shims reads:
"Measure dimensions, determine parallelity of sprocekts; usually two washers are required (cylinders 4 to 6)"

Unfortunately, page 15-2e which describes measuring the parallelity has:
"As a rule, three shims are required below the left-hand sprocket (cyl. bank No. 1 to 3), and four shims are required below the right-hand sprocket (cyl. bank No. 4 to 6)."

Go figure.
-Eric
90 C2 (currently a work in progress)

[stevepaa]

My 92 C2 also had 2 each side. I did the parallel measurement and I think it was 3 and 4 in the end. I bought new shims to use.

[adomakin]

sorry to hijack the thread but how or why would the shim requirement be different than what the factory suggests? are cams longer/shorter by small amounts?

[axl911]

I recalled having 2 on each side on my 92 C2 when I rebuilt it.

---
anthony

[adomakin]

???

[ChrisBennet]

Originally posted by adomakin
sorry to hijack the thread but how or why would the shim requirement be different than what the factory suggests? are cams longer/shorter by small amounts?

The factory gives the measurement specs and states the usual number of shims that it takes to arrive at that number - it doesn't actually "suggest" the number of shims.

To (not) answer your question, I don't know where the differences would come from that the shims are compensating for.

Apparently, the # of shims the factory used for the 964 does not match the # of shims that you would use if you followed the 964 factory manual instructions.

This is the mystery that prompted my post.
-Chris

[adomakin]

hmm....Maybe im not thinking straight but i can only think that there are very minute differences in camshaft length? actually, thinking about it, that can't be right as the cam sprocket spider slides up and down the cam....hmm...