Main bearings questions

[Ho Hum 74]

Hi all,

I have found that my 2.7 case has been line bored to 62.5mm. This is the maximum that it can go. It's not even in the Porsche Tech Specs book! But the bearings are sold on this website (unfortunately they are rather more costly than the std ones ).

My questions are about the bearings themselves:

1. Is the soft, inner material the same thickness on ALL bearing sizes, from std to .25mm oversize to .5mm oversize?
2. Is the gap made up by the steel backing or soft bearing material?
3. Is there anything wrong with an engine with these .5mm oversize bearings?

Thanks
Tristan

[john walker's workshop]

the steel backing is thicker. the babbit material has the same depth as standard.
the problem with 2.7 cases, among other things, is that the main bearing bore generally needs a cleanup to align all the bores. the bearing bores might mic out ok individually, but they may not all be in a true line. the first clue is when you torque up the case bolts and nuts and find that the crank won't turn, or is difficult to turn. if the second over align bore is recent, maybe you will get lucky. otherwise you will have to start again with another case. i see no problem using a second over case if it's in spec.