Bored????

need4speed · Post by **need4speed** » Mon Dec 03, 2007 2:47 pm

Stripped down a 3.9 for my dad recently and im a little puzzled.
The motor is supposed to be quite a high miler, however there is VERY little wear-ridge at the top of the bores - in fact its almost non-existent. This led me to believe that it maybe had a re-bore at some point, but there is no +20 mark on top of the pistons like i would expect. Do ALL oversize pistons have this marked on them?
Also, there has been some water sitting in the bores and this has caused some pitting of the liners (unfortunately near the top). will this hone out or will it need rebored? The pitting doesnt feel too deep, but its difficult to guage..

ChrisJC · Post by **ChrisJC** » Mon Dec 03, 2007 3:22 pm

I've never seen an RV8 with significant bore wear. It always seems to be the camshaft that's worn out and the rockers.

Pitting sounds bad, I doubt if it will hone out.

Chris.

need4speed · Post by **need4speed** » Mon Dec 03, 2007 3:28 pm

ChrisJC wrote:Pitting sounds bad, I doubt if it will hone out.

Thats a shame because he has a lovely set of pistons to suit the 3.9, but they are standard size...

sowen · Post by **sowen** » Mon Dec 03, 2007 7:40 pm

My 3.9 has +20 pistons fitted, and the only markings on them are DW895 + .508, and a set of brand new +20 pistons I bought for it had DW895 + .508 020 marked on them. Give the honing a go, the pitting may only be on the surface and come right out and save you a rebore, but depends really on how far you want to go with the engine.

Simon

need4speed · Post by **need4speed** » Mon Dec 03, 2007 8:14 pm

i would think the .508 refers to .508 of a mm, which is 20thou. so it does say on the top that its a rebore. my dads pistons doesnt have this on them...