[T3] Endplay measurements

[Phil Hof]

I’ve posted this info on the Samba (twice: T-3 and Perf forums), but this group isn’t always on the Samba, so with apologies to those who responded there, here is my latest update on the endplay of my ’71’s stock FI engine:

I don't have my old measurements (just memory of a shimmed endplay w/flywheel of about 0.006" to 0.007", slightly out of spec. I made no check of any endplay in the bearing, just a measurement off the flywheel itself. This was 7-8 years ago and I have driven maybe 5000 miles or so since then. 

With the flywheel on and shimmed, I now have 0.014" endplay, so it has gotten quite a lot worse in a short time (mileage)! 

With the flywheel off, I measure about 0.012" of endplay in the bearing itself, so almost the entire endplay is in the bearing it seems. It will have to await teardown to find out if the wear is in the bearing or the case (or quite unlikely, in the crank itself). 

No way to know for sure, but 7-8 years ago I may have unknowingly been measuring mostly bearing endplay, and set the shim endplay to nearly zero, since it seems to be only about 0.002" even now. 

So to put some bounds on this, how much of an oversize bearing can be used to take up excessive endplay? I understand there are oversizes in this dimension available, as well as the usual OD following a line bore. Can as much as 0.012" be taken up by the oversize bearing? I heard from one source here that up to 2mm (0.078") can be accommodated. If so, there is hope for my case. 

But of course, there are many more measurements to be taken before we know all.

[a reply:  Thrust bearings come in 1mm and 2mm oversize. Typically, the way to do this is to get the oversize bearing that you need, have the case cut until it is flat and even on the thrust, then have the bearing turned so that there is an interferance fit. Basically, cut the bearing to fit the case. This way, the case can be cut more than twice.]

I am so glad I took the advice here (thanks, Tram!) to STOP before any more wear took place. Even the 1mm (0.039") oversize should be plenty to take up the slack I now have (0.012") even if it is lopsided on one face of the case saddle.

I’ll be taking the case into the home shop of a local club member, and have him split the case and take the proper internal measurements.  It will probably need a line bore, and I tentatively plan to put in a new CW crank, so in addition to the case (hopefully) the heads will be next to be checked.  Other than a check for cracks, what else makes the decision to rework or replace them?

Whatch’all think?

-Phil
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