jb1 piston coating hm elliot/piston clearance

[1stop]

I have some pistons coated by hm elliot with .0015 per side build up. Its for a twin cam harley. Forged pistons. Do i need to add clearance for the coating,or clearance for bare piston? There isnt much info to be found online. Any one using there coating? Any help would be appreciated.

[jsachs1]

Look on the wrist pin boss, and sometimes the bare piston skirt size is stamped there. I know with KB line to line coated pistons, bore to nominal, and Scotch Brite any coating high spots. Not familiar with Elliot. Give them a call.
John

[1stop]

talked to a guy there, and he didnt know. i seen some people here were using them, but it was old post. its s different coating that they use now. would be nice if i got a opinion from someone that has run it before. thanks for reply.

[Geoff2]

0.0015" 'per side' is 0.003", which is quite a bit. If the original piston to bore clearance was, say, 0.003" then that clearance has gone.

[mag2555]

Anti friction coating on piston skirts does change there running expansion rate, so any added diameter thickness must also be put into the Bore clearance.

Only if the top of the piston has had a termal coating done to them will the expansion rate of the piston be reduced.

[ProPower engines]

0.0015" 'per side' is 0.003", which is quite a bit. If the original piston to bore clearance was, say, 0.003" then that clearance has gone.

Not always the case. Any and every piston manufacture tells us to not measure the pistons with the coating to calculate clearance. They have a bare spot on most to measure the actual piston skirt size even though the skirts are coated
and the piston measures larger.
On a used and recoated piston being used in a new block then some consideration for the extra coating will be needed
but if its just to tighten up an existing piston to a worn or larger bore then no it should not.