re ring question

[tom yuenkel]

Say, I have a "piston ring set" question but first a little back ground, My 1987 military 6.2 blew out a head gasket after 12000 miles since installing it in my 91 suburban.( I know I know I should have been smarter) so I pulled the engine to work on it and found rust in two of the bores. Now, even though it only has 40000 original miles I want to re ring it because of the rust causing blowby. I intend to leave the crank and cam alone. I found the block is set up with four oversized pistons and four standard sized pistons. Who out there sells a mixed set of rings? and is this normal?

[john8662]

Now I see what the quality of a military reman is...

using different sized pistons in different cylinders isn't a normal practice. the normal practice is to bore them all so that the engine is balanced.

You can order ring packs individually, so you could theoretically buy 4 sets of the OS rings and a 4 sets of the standard bore rings.

What OS are the larger pistons? There will typically be a stamped part number and a metric number stamped on the top of the piston to identify the oversize.

.50mm = .020"
.75mm = .030"
1.00mm = .040"

If it was me, I'd pull it all down, mic the cylinders and bore the others to match then buy a set of pistons and rebuild the engine correctly.

But, to get by, you could sure pull the pistons out of the rusty holes, lightly hone the cylinder, re-install new rings and go with that. but I can tell you it'll be really hard to keep everything clean during a hone like that, especially the crankshaft journals.

[tom yuenkel]

John, my fault this is my first tear down and I just needed to be patient. In fact All the pistons are .30 over but one bore is so heavily rusted the block needs to be bored and the pistons replaced. I also found a failed rod bearing requiring the crank to be polished or ground. Faced with the cost of the repair work I choose to go back and contact the seller (Ted's Military stuff). Ted's sending me a replacement motor to resolve the problem. I got lucky.....Tom

[john8662]

Yep, sounds like you got lucky! I got screwed on a couple military engines too, think they'd send me one too?

haha, just kidding of course.

From the sound of things, it was up against a total rebuild. Going to a .040 size piston and boring the cylinders.

Glad things are working out.