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Rv8 cylinder bore
Posted: Wed Sep 18, 2013 6:53 pm
by wangie46
I'm currently rebuilding a 3.9 my first engine build to go in my lr90 to replace the oil burner thats in it, on strip down ive noticed some vertical scratches on the lower part of the cylinder bores, a few are quite deep and can be felt with your finger nail, the machine shop recons a rebore is needed so that's a rebore and plus 20 pistons before I start, but a friend of mine who's a mechanic reckons that a lot of the old v8s have these scores at the bottom of the bore and as long as the bore measures up a light hone and new rings will be fine as they will not affect compression, looking for your opinion is my mechanic mate right or wrong?
Posted: Wed Sep 18, 2013 7:14 pm
by teamidris
He's not wrong, but.......
I don't know how they do it? I wonder if bits of cam shaft get thrown up the bores? Either way up, the compression pressure builds as the piston approaches TDC, so scoring at the bottom isn't as bad as at the top.
Will the pistons be any good? Can the bores be any good? If it needs pistons it seems a shame to fit them into scored bores, even if the ovality is okay.
The 3.5 we just re-built only just made 20 thou overbore due to big ovality, so it's likely that you'll never have to make this difficult decision. Unless you're after a knock-about engine that's as cheap as possible. With a low compression engine you can be a bit free with quality
