Pat Kennedy

I'm the 3rd owner of this 88 951 2.8L. The first owner had the work done to go from 2.5 to 2.8L. I was told it was a stroker, with an S2 crank, new special pistons and rods. My tech and I pulled the head last week because we were searching for answers to an oil system problem.

He measured the cylinders with the correct instumentation and says the cylinders were already oversized! He says maximum oversize bore is 100.520 and mine are 100.536. He thinks the cyls were too large when some work was done for the 2nd owner, and that there is almost no wear on the cyliders. I bought the car with 77,000 mi. on the odo and the 2nd owner had a total rebuild done at 71,000.

My tech says either we have this block re-sleeved or start looking for a used one.

I just put a new turbocharger on because we thought that was the root of the the oil system problem (massive blue smoke out the tailpipe) and indeed the old turbocharger was shot to hell. But as we're digging deeper, more trouble is being uncovered. Compression numbers were good, but after a leakdown, he says our problem is definately the bottom of cylinder #4.

I'm seeking advice regarding the pros/cons of sleeving the current block vs starting over with another block.

Thanks.

cruise98

Patrick:

There is only one oversize for these engines and you already have it. The bore size is 100.52 for tolerance group 2 pistons. The wear limit is 0.080 clearance between the piston and cylinder wall. Measure the piston and see what you have.

Another option is having the cylinder block nicom plated. That way you can reuse the same pistons you already have. You would have to find the correct rings and there are some other hurdles to jump, but it is an option.

Pat Kennedy

I've recently learned there is a 101.00 over bore piston. Sounds intriguing, but not cheap.

I've also learned that nicom is good for .010 at the most. Not gonna make a difference in the clearances I need.

Looks like I'm in the market for a used short block.

Thanks.

Mike B

A very knowledgeable tech told me the 101 pistons have had a real sketchy past...You have to remove too much material and about 1/2 of them cratered for that reason...I don't think Porsche recommends the 101 pistons as it is a real crap shoot...

I think you are on the right track sourcing a used block and that will be much more cost effective.

$pit

I just had my engine rebuilt and nicom plated, with custom pistions. really botched job now i'm getting another rebuild. Get a used block. This site is pretty good at finding parts.
<a href="http://car-part.com/" target="_blank">http://car-part.com/</a>

Good luck