3.2 crank clearance - possible manual misprint

[bdonally]

Just checking new bearings, and I found that the axial play is 0.008", with the case fully buttoned up and using a dial indicator on the nose of the crank.
My factory manual and Bentley show 0.0043" to 0.0078" with a wear limit of 0.008.
The thrust surfaces on the crank measure 28.03mm (spec = 28.00 to 28.06) and the new bearing is 27.84. Based on these measurements, the float would be 0.19mm, right at the upper limit and the wear limit.
In Wayne Dempsey's book, the install spec is given as 0.110 to 0.195mm (0.0043" to 0.0078") with the wear limit at 0.3mm. these specs are the same for all the engines listed.
The bearing supplier checked a number of bearings from two suppliers), and they are all in the 27.8 to 27.9 range, so with an in-spec crank the best one can get is about 0.19mm, or 0.008" of axial play.

I guess its possible something changed for the 3.2 but since the wear limit is so close to the upper build spec, it looks to me that the factory manual has a misprint, and the wear limit should be 0.3mm.

Hate to put together the motor with a spec so close to the wear limit.

[itsme]

If the high spec on the crank is 28.00mm, new largest bearing 27.90 wouldn't that be .1mm or .0039" play? I have a brand new OEM thrust and it measures 27.86 and I have used 3.2/3.3 crank and thrust is 28.03 also so your measurements are not out of the ordinary apparently. My 964 crank is 28.00 so I don't think its out of the line.

[bdonally]

Yes I agree that a min spec crank and a max bearing results in 0.1mm.
But in your actual crank and bearing, the clearance is 0.17mm, within the high limit for clearance, but quite close to the published wear limit of 0.2mm.

Really just trying to determine if the 0.2mm wear limit in the manual should be 0.3mm.

[KTL]

I have various workshop manuals:

'78-'83 911
'84-'89 911
'89 930
'84-'87 911 spec booklet
'78-'81 911 spec booklet (did not check this one)

Even though the cranks have different rod bearing sizes, the width in the cranks for the #1 thrust bearing remains the same at 28.06mm max.

The spec for the thrust clearance probably came from the spec books, because the workshop manuals don't make mention of that clearance. Here's a snapshot from the '84-'87 booklet




Does your old thrust bearing show any significant wear on the thrust surfaces? If not, i'd not be too worried about it. Thrust wear does not seem to be an issue with these engines like others in the world, like say the Mitsubishi 4G63 2.0L where crank float is a known problem.

I've got a 3.2L engine apart right now and I noticed some significant thrust wear on the #1 bearing. Copper color showing on the bearing shoulder surface. But there doesn't seem to be anything else amiss with the case that I can see yet. I think the case may be misaligned like bpu699 encountered here

IMS shaft won't spin...case misaligned? Input appreciated...

So what apparently happens is the bearings are "self-clearanced" when the clearance isn't checked and this case misalignment is present? I plan to have to take a closer look at my case before I final assemble it!

[bdonally]

Thanks for the info.
The crank isn't worn, although the thrust bearing had a bit of copper showing.
Interestingly, the worn bearing measures 27.84/27.86, the same as the new bearing.
Ive decided the 0.2mm limit is incorrect and to move on to the next problem.

Below is a photo of table E on page 130-11 of my 84-89 shop manual.
It shows the wear limit at 0.2mm; this is what caused my concern.