Can anyone recommend a rebuild kit for the 1989 3.0 liter that's bored .30 over?

Thanks.

Well, I can't find any kits so far that are .030 over, only 20 and 40, so 40 it is. But which one?

US manufacturers measure overbores in inches - .010", .020", .030", etc.

Import overbores are usually in metric dimensions (mm) and are sized as .25mm, .50mm, .75mm, 1.0mm, etc.

.25mm = .0098" (about .010")
.50mm = .0197" (about .020")
.75mm = .0295" (about .030")
1.0mm = .0394" (about .040")

Unfortunately, "about" is not a good way to measure overbores - so:

If you want a .030" overbore, you need to look for a .75mm oversized piston. They used to be available from Mitsubishi - not sure now. Custom piston makers can make whatever you want for about $600/set.

Be very careful that you (or better yet, your machinist) decide in metric equivalent what overbore size you need - and be very careful that you have the pistons in hand to give to the machinist before he bores your block.

Any rebore done the right way will have the pistons in the machinist's hands so he can measure them to see how much more he needs to allow for piston clearance.

Frank

ditto, especially having the pistons in had before it's bored...

Thanks Frank, good to know. I'll be working with my guy to do the machine work, learning as i go.

Any suggestions on a company to order from? I've seen a half dozen kits on rockauto and E-bay, each offering the .020 and .040 overbore options, but I don't know who to trust.

For 3.0L rebuilds, I've mostly used OE Mitsubishi for stock rebuilds or custom Wiseco for blower engines - both are expensive and not necessary for a stock rebuild. There are a lot of good and more reasonably priced piston manufacturers - so I'd ask the machinist what he likes. A good machinist is your friend.

Frank