Steve944

i am looking for a set of pistons, getting the engine rebuilt, several of mine were damaged, missing part of piston that separates rings, i think it uses a 97mm piston, can the block be bored out to go with the larger pistons
stephen

SMTCapeCod

If it was running with one or more broken piston lands and/or rings, seems really likely that the bores sustained some damage too? Given the costs of components, getting a used shortblock might be the way to go. Boring is not an option, the bores are coated/sleeved.

Vilhuer

Wrong. Boring is option but its not cheap. See WSM for details how to do it.

Fabio421

It should have 95mm pistons BTW.

GlenL

Broken lands (the bits between the rings) don't necessarily mean the bores are scored or scored beyond use. Big scratches are still scratches. I've used a block after finding broken lands. No issues with that.

The blocks can be bored. I've had this done. It may not be cost effective compared to getting another used block. Going bigger sounds good but you'd be better off getting a 4.7l block for that. Or 5l block. Then there's matching the pistons to the heads and cams which may mean notching, but I doubt it and really don't know for those combinations.

Your engine should be a 4.5l version so 95mm pistons. These are commonly available. The trick is the tolerance group. You'll find a 0, 1 or 2 stamped on the block above each hole and on each piston. That's the tolerance group number. Consult the manual on this, too. 2 is the biggest and you can go with a bigger piston due to wear but never a smaller one. I suggest getting a few more than needed and doing test-fittings to find the pistons that work well. Takes a sensitive hand to feel what's right.

Steve944

the engine is a 4.7, block and heads have already been done, pistons measure 3.816"s, having trouble finding pistons, was looking for other options

James Bailey

If it is a Euro S then it is 97 MM and more rare in the USA. Also higher compression and manual ignition timing adjustment which could explain broken rings.... too much advance, poor fuel, too much bwaaah !!!equals shattered rings. And as noted the blocks can be bored and honed oversize, no sleeves no coating just an all alusil block. But never ever use a simple bottlebrush hone on a drill motor like you would a old Chevy

SMTCapeCod

Fine, my response used terms that were too absolute. Apologies for the misinformation.

Ethre

Steve,

As I recall 928 Intl got a couple of sets of NOS pistons this spring. Might be worth giving them a call.

928mac

So I was on the side of the road when this bum walks by and says "was-up-man."
I said piston broke.

He says "I know the feeling"

pissed and broke

pdejong

Steve,
I have a complete set of 97mm pistons from a 1983S (US). Car had about 60k miles on it, before I took them out. They're in a good shape.

Send me an email if you're interested: psdj46@gmail.com

Peter deJong
'83S (RIP)
'90 GT-twin turbo

Steve944

car is a euro, had so much base pressure it blew out the seals, timing belt was split in two, like two belts on one set of pulleys, pistons were rubbing on one side, car has been in shop since dec , ready to get it back, only one machinist in town that will do european motors

Vilhuer

Which doesn't mean he will have any idea what so ever how to machine alusil block.

Steve944

i hope he did

James Bailey

Sorry but you are screwed !! You ONLY bore hone blocks AFTER you have correct pistons of the size you bore and hone the cyinders for . Friggin idiots !!!!! Many of the oversized pistons have been unavailable for years !! This stuff is pretty easy yet so many manage to screw it up.....