This is correct. The pistons will already have the clearance "built-in". Your job is to make sure the bore is the correct size, as listed on the piston spec sheet (85mm, 85.50mm, etc.). Typically, forged pistons will provide .0035"-.004" clearance for a 4G63T. JE is right, some of the rings are already at the proper gap, you don't want to bore the block much further because your ring end gap can increase more than you'd prefer.

 

Thanks guys, but these assumptions are only theoretical, I have seen forged pistons that have a real measure bigger than what the correct clearance is.
For now the only infos that I have on JE tell that the pistons are usually 0.002" smaller than the nominal bore size.
Can someone confirm or not?

 

JE told me that the "in-built clearance" is 0.1mm (0.004"), another guy told me that the in-built clearance for JE tipically is 0.05mm (0.002").....logic tells me to listen at JE, but can I have a confirmation please?

 

The spec sheet for my JE's is 4 thou. The pistons are .5mm over and you DO have to file fit rings!
All my pistons measured out to 3.361", I bored/honed to 3.365"

Why can't you convert your mm dimensions to in? Theres 25.4mm to an inch fwiw

Good luck w/ ur build

 

Thanks mate, so your pistons .5mm oversize (85.5mm - 3.366") measured at 3.361" !!! An in built clearance of 0.127mm - 0.005" if you bore-hone to nominal size!!!

 

Yup. You're not supposed to bore to the nominal bore size, you need to measure your pistons and calculate accordingly!

The JE spec sheet said to set piston to wall clearance to .004". If I had blindly bored to 85.5mm that clearance would have been larger by 1 thou.

 

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