This is 'merica! We use standard measuring here!

Haha. Just busting your chops, but seriously. I had to do the conversions just know the numbers. I hope you are using a proper bore gauge and mic to measure. At 0.0024" on the wide end, thats right over the service limits, but you can hone(take to a machinist. do not use stones) the block and re-ring the pistons if you're on a budget. Motor would run fine but you'll just get a bit of blow-by so make sure your PCV is up to par.

Honestly, if the motor was good and strong before, I would just throw it back together and run it. Your goals are so mild its unnecessary.

lasthope05 said:

This is 'merica! We use standard measuring here!

Haha. Just busting your chops, but seriously. I had to do the conversions just know the numbers. I hope you are using a proper bore gauge and mic to measure. At 0.0024" on the wide end, thats right over the service limits, but you can hone(take to a machinist. do not use stones) the block and re-ring the pistons if you're on a budget. Motor would run fine but you'll just get a bit of blow-by so make sure your PCV is up to par.

Honestly, if the motor was good and strong before, I would just throw it back together and run it. Your goals are so mild its unnecessary.

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This is my spare engine, while it idled I don't know if it was strong But by the looks of it, it was overdue for a rebuild.

Stock Nippon pistons are like $100 on ebay. Will those be closer to 85mm and reduce the ptw clearance? What is the actual diameter of new pistons?

Every piston is different. They have tolerances in the factory also that they go by for good or not good, so really you won't know until you get them and measure them. My first mechanic that I learned under (35+ years ago) was from the Marines and he would ask the machine shop to bore each cylinder to match the piston not just "bore it .020" or whatever the case. He would check each piston and tell the shop to bore each one accordingly. A lot of machine shops just take the original bore and then bore all the cylinders an additional amount, but don't actually measure each piston. Not ALL shops work that way, but the ones in my area were known to do it that way.

My shop also needed the pistons first, which was a good indication that they knew what they were doing and why I took in there. Granted these were .040 wiseco's and I knew i was getting it bored anyway.

I'd have the machine shop double check the bore, and also taper, before you go buying any pistons. They have tools to measure 3 or more decimal places, and they surely know what they're doing more than I do.

tmoney20g said:

My shop also needed the pistons first, which was a good indication that they knew what they were doing and why I took in there. Granted these were .040 wiseco's and I knew i was getting it bored anyway.

I'd have the machine shop double check the bore, and also taper, before you go buying any pistons. They have tools to measure 3 or more decimal places, and they surely know what they're doing more than I do.

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I've provided pistons before for boring but they were custom cp. I thought oem would have a standard size since they just assemble the shortblock at the factory.

I guess I have to decide whether to risk it, or get larger pistons, possibly 2g.

I'd buy new pistons just to be on the safe side due to piston to wall clearance