My question is to anyone who has experience with these pistons. I have a 30 over 455 block collecting dust in my garage. I know someone selling a very lightly used set of these KB277 .030 pistons for very inexpensive, they look like they just came out of the box.

So I went out to measure the bores on my block and they are right around 4.1555”

The clearance should .0020 - .0025” for a street appplication.

The seller is saying they are 4.140” so that’s right in the range.

Maybe someone who has worked with these pistons can chime in regarding fitment. And if it’s worth going out to meet the seller.

4.140 would give you .015 clearance, wAy too much.

I’m sorry I meant 4.1535” not 4.140”

He said in his email to me they are 1.5 thou below 4.155”

The KB catalogue lists a bore size of 4.156” which is different from other manufacturers which advertise a bore size of 4.155”