New/old Pistons

[Tricky1.5]

Hi guys,
As I have inherited a project I have some 'new' old parts. At the top of my list for the engine rebuild is a new set of pistons that I estimate are 17 years old. I understand they are .003 over but I cant figure out what the compression ratio is.
If anyone with some technical knowledge or advice I'm happy to hear it.

[Jaglex]

From the picture it looks like 9:1, as the 8:0 pistons top surface is flat.

[christopher storey]

8:1 pistons are not flat but have a dome which looks very much like the one in the photograph . 9:1 pistons also are domed , but the dome is both bigger and higher with IIRC cutouts for the edges of the valves. I do not think the .002 refers to oversize. I think that probably refers to the ring gap, and these look as though they may be .030" oversize. What is a bit peculiar is that mark at the lower part of the piston's periphery

[abowie]

If I had to guess, from the picture I 'd say these look more like 8:1s as well.
I reckon that the 2 thou measurement is probably more likely the bore clearance than the ring gap but David may well be right.

[Tricky1.5]

Thanks for the feedback. I spoke to the guy who did the machining on the block and head today and by measurements and calculation he says the compression ratio will be 8.94:1 with the head gasket he supplied.
I wanted something a bit closer to 8:1 but I'll run with what I have.
Hopefully it doesn't ping its head off...

[Hugo]

How on Earth did he work that out? I know the sums are quite easy, but considering your pistons are still in a box, how could he measure the volume of the combustion chamber?

[abowie]

Hopefully it doesn't ping its head off...

That should be fine as long as you run 98. If you're worried you can get Cometic gaskets up to 70 thou thick off the shelf.