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Posted by ChrisCase [76.212.213.18] on Wednesday, May 18, 2011 at 15:53:35 :
In Reply to: 318LA question posted by Mike Hernke [63.151.218.18] on Wednesday, May 18, 2011 at 15:29:18 :
The ridge is the part above the ring travel, where nothing ever touches. The rings wear the bore up to that point. The taper of the bore is equal to the difference between ridge and the unworn zone above. No ridge would mean little wear to the bores. So clean off any carbon and take a close look.A ridge as thick as a thumbnail is about the limit.
A dial caliper can give you a pretty good guestimate of the size. They won't measure ridge though, which would be an indicator of wear since boring.
Also clean off the top of a piston, look for numbers that designate oversize. .040 = bored 040 oversize. No mark = no rebore on the 'rebuild'.
So, if the bore measures stock plus .040, and pistons are marked .040, you ought to be good to go.
The "rebuilt" might have been just rings and bearings, or maybe a bore and new, crappy pistons, that have collapsed already.
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