OK. I stuck this on the other 307 piston thread. I get confused easily. I was doing this in response to Intergrated j 78's request.
OK, Here's what I got. My measurements are somewhat crude but should give you an idea. I used a caliper as well as I can. The 307 pistons are .040 over as marked on top. There is a dish and two valve cuts. The dish is 2.995-2.93 wide and .050 -.058 deep. Without the valve cuts that about 5.8cc to 6.4cc. That is probably a little bigger than the 250 dish but it does not have the hugh chamfer that the 250 and some other 307s have. The rim on top is about .045" wide and would give a nice quench area. To get the pin height I measured from the top of the pin hole to the top of the piston and added 1/2 of the pin diameter. The 307 measured 1.64856" -1.65365" and the 250 was 1.63875". It could be closer to the 1.655" advertised. So the 307 is roughly .010" taller with a more efficient design. I think it would help some but not a lot. The box they came in may not be the original box. It may be worth more a sports memorabilia than the pistons are worth. It says Zollnor and Fred Zollner was the founder of the team that became the Detroit Pistons. There is a hand written part number on the box. It is a Sealed Power number. 295 AP 40 is the one with 4 valve cuts. The rings are Sealed Power KromX. I mounted one to check it in the 153. The rest haven't been messed with. The pins are stuck from dried lube but will come right out with some degreaser.
I'm not in the piston business so if you want them I'll make you a good deal and there is no hurry they are not going anywhere till you know if you can use them.
