Piston Question

The 285 NP/NCP may have a higher compression ratio piston; The Silvolite equivalent has a compression height of 1.741" and the 285AP has a compression height of 1.720".

Put in a pin part way in one type and then the other end of the pin into the other type, so the pin is in both pistons side by side at the same time. Rest the tops of the pistons on a truly flat surface at the same time. See if both piston tops set flat on the surface with absolutely no difference. If one top is not exactly flat on the surface with the other, then you have a different compression height and the compression ratio will be different.

Then weigh both types on a gram scale to see if they weigh the same within a few grams.

If the compression heights and weight are the same, look at the pin bores. I bet the NCP has grooves for the pin locks and the AP does not have those grooves. If that is the only difference, then I would be OK with the AP.

BTW, the 285NP is the same as the 285NCP except the NCP has a skirt coating and the NP does not. So you will be good if you can find an NP.

Have you tried eBay?