No 8 Bearing

[PJMARKOW]

I've just received my case back after having it line bored. All oversized mains and No. 8 bearing were also supplied. I tested the fit of the No. 8 bearing in the left side case and boy is it a tight fit. I realy had to force it in there (no O ring on at this stage), to get it seated properly, and when I pulled it out there were score marks on each side where it touched the case. How tight should this bearing be? All the other main bearing shells fitted perfectly.

[ChrisBennet]

The ones I've seen just drop right in. Can you measure the bearing?
-Chris

[Rot 911]

Something sure isn't right, my #8 bearing was a snug fit, but I didn't have to force it.

[dtw]

Mine dropped right in too (std/std)

[Tim Walsh]

Hmm.. Did they bore the No8 bearing for oversized bearings? I wonder if they didn't bore that one since it sees very little load and wear.

[ChrisBennet]

Originally posted by l33t9eek
Hmm.. Did they bore the No8 bearing for oversized bearings? I wonder if they didn't bore that one since it sees very little load and wear.

They shouldn't do No 8. I don't think that ones comes in an oversize version.
-Chris

[PJMARKOW]

Well the No 8 bearing housing was bored and a new bearing was supplied. New bearing part number 901 138 63 and it measures 63.3mm, the old one measures 63.00mm. All this was done by a local official Porsche centre. The bearing is tight at the edges of the case joint, and it's the same on both the left and right cases. It won't just drop in, it just sits about 1mm off the bottom of the bearing housing unless I really jam it in there. The original one just drops in. I looks like the bored case was OK until the bolts were undone and it's relaxed in a bit.

[john walker's workshop]

bolt the case halves together, torque the bolts to spec, then measure the ID of #8 bore. compare the measurement to the bearing OD to find the interference. if it turns out to be within spec, try deburring the edges of the saddle so they don't dig into the bearing.

[PJMARKOW]

Thanks John, that's was my thought as well. I spoke to Porsche and had them check all bearing part numbers and they're all .25mm oversize, so that rules out an incorrect bearing. I might just wait until I get my crank back, debur, the case and then trial fit the crank with all bearings installed. Should tell me if everything's aligned properly.

[john walker's workshop]

all bearings need a slight "crush". it's designed into them. they don't just sit in the case loosely.