Working with a RB .030" over. Here's my dilemma. The block has just been bored to 4.35"to fit a set of used pistons. It seems one of the pistons may be bad. I can't find pistons to fit the block. All .030" pistons are 4.35" in diameter. I need pistons with a skirt of 4.3444". Does anyone know where or who has something like this? I don't want to send the block to the machine shop. The pistons that are in there now are older Pro Tru's

cant remember for sure. wiseco piston had clearance built in ?? i think most off the shelf were coming that way..??

Every brand I know of make the pistons under size to fit the over size bore, you have a bad set if they aren't smaller on the skirts than the 4.350 bore size
Send them back and get the correct size
Maybe they where made for a 4.355 bore size

Hone the cylinder to fit if they are too big and you have to use what you have. Using some used parts, got to measure everything first as I've BTDT with the orphan part or sizing different than expected. Even had new parts come in that were odd sizings among the batch.

A .030" over piston for 4.350" bore size should be 4.345" or smaller if it's a forged slug. Most will want at least .005" wall clearance. The clearance is "built in." If they are really 4.350", then they aren't for a .030" over 440.

Yes. As stated above the clearance is generally built into the piston.

Shelf .030 over 440 pistons would be more accurately described as "for use in a 4.350 bore" and will measure smaller than 4.350.

Lets say .005 clearance was specified....then the piston should measure 4.345 at the prescribed measuring point.
The measurement point is usually described in context with the wrist pin location and can vary somewhat.

Thanks everyone. I got it rectified. Called the manufacturer and had him measure a piston from his stock. It measures 4.345. I had him ship that piston directly to me. The other piston must have been boxed wrong?

just goes to show --- always double check everything !!