3sgte bore clearance

Hi,

I'm measuring piston to cylinder clearance on a 3sgte with 86.5 mm wossner pistons, they are coated pistons and if I measure the skirt including the coating then check my clearance it's at 0.05 mm. The box the pistons came in says to bore the cylinder to 86.5 and pistons are 86.43 and .07 is the clearance, coating is between

.02 and .025, is this correct because there was a spec sheet in the box saying .095 to .1 is the clearance. .05 seems very tight, please can anyone advise me on what's correct and how to measure clearance correctly. Thanks in advance.

John

You're going to need to check what the coating actually is, as there are different ones for different purposes.

IIRC, Wossner [edit, might have been Wiseco, but same principle applies] have one where the piston is supposed to be installed with less than the expected clearance, with the coating being designed to adapt to 'self-clearance', but other coatings have different purposes.

Have you carefully measured the bores, at several points, to make sure they're to the nominal diameter, with the tolerance being to the larger and NOT to the lesser value?

If the pistons are as Wossner provides them, I'd ask them what they suggest. Hopefully they can offer insight on what Gord mentioned about the purpose of the coating as well, otherwise I'd ask the coating provider if it's a 3rd party.

I've run .05 on much bigger bore pistons than that with success at 200 HP per hole, so it doesn't seem that tight to me, but I do personally run less PTW than many others seem to prefer.

How much power are you planning on, what fuel, turbo and boost level?

How will the engine be used?