piston coating with no measuring spot

[Belgian1979]

Question: just received my engine block back from the machine shop with my new pistons. CP bullets custom made with skirt coating. Coating has no measuring spot. Piston card says .004" ptw clearance and measured .400 from the bottom of the skirt and that's it, no other info. Machine shop says CP stated this was the clearance measured from the diameter including the coating which is where they set the clearance. Still have to measure it tomorrow to be sure where I'm at. This will be a bit difficult as the block was done with torque plates installed and I don't have torque plates to get very accurate measurements.

I always thought that ptw was measured without the coating, but all of the coatings I saw had a measuring spot in them. These do not...so I'm not sure.

[rebelyell]

Have you written CP and asked for clarification of install spec for Your pistons ?

[Belgian1979]

Going to but it's weekend.
Just wanted to know what the views were here.

[modok]

CP is good enough that they should be able to measure a piston all by themselves
and just tell you want bore size the piston should fit.

[hoffman900]

Going to but it's weekend.
Just wanted to know what the views were here.

I’d rather wait than assemble something based on internet responses, ymmv.

[Belgian1979]

Found it. The clearance has to be added to the machined diameter of the piston. So coating is not included. I checked some bores and it seems that way. Going to measure all of them.