early 273 pistons.

OK a very good observation; thanks. I have just been roughly estimating. I too your measurement numbers and remeasured here and got just a hair larger. Then computed the volume and came up with 2.2 cc's, so with the fillet, I bet 2 cc's is very close. That is good data to have so many thanks for guiding me to the light!

Just for more info, I have measured the volume in the valve dimples in the 675 heads that came off of this '68 273 and they were 2 cc's total for an intake/exhaust pair.

Reworking the SCR with:
- 2 cc's of eyebrow volume
- 58 cc heads
- .028" thick gasket and 4.1" bore (Mr Gasket 1121G)
- -.020" below deck
Now SCR is 9.06
If gaskets become .040" thick then SCR is 8.77. Both are pretty good numbers!

If I rerun our '68 273 with these eyebrow numbers and the 68 cc measured chambers and 2 cc eyebrows, I get 8.5 with .021" shim gaskets, 8.1 SCR with .040" composite gaskets (Felpro 1008), and 7.9 with Felpro 8553PT gaskets.

Question: Are you gonna run a turbo with 9:1 SCR? IMHO, that is higher than I would want. The late 273 SCR numbers with the composite gaskets look to be a better choice, IMHO. Or use a small turbo and limit the boost a fair amount.