I decided to measure the chamber volume in my new Sherman head. I get 125 cc's (7.63 cu in) .
So if the gasket is 1/16" thick and the piston comes up 1/4" above the deck then the CR is probably in the 8-1 range.
The old Sherman I have is about 200 cc's (12.2 cu in.
Based on the above assumptions then CR is probably about 5.5 to 6-1.
Your results may differ!!
Thanks, I get 8.8:1 with Larry Young's formula from the Tulsa club's website: http://mtfctulsa.com/Tech/head_design.htm
That'll make an old model T speedster fly
Is there enough room for high lift and good flow around the valves?
The clearance around the valves is probably OK. There is about 1/2" above the valves so it will probably be OK with most camshafts. I would not assemble until I had checked clearance with putty between the pistons and the head and between the valves and the head. Way easier to address something before you bend something!!
I would suggest you consider one of the copper shim head gaskets that Kevin Pharis makes. They seem to work well and allow for more flow area around the valves. And Yes this lowers to CR, but the extra flow more than makes up for that. In a flathead engine as you increase CR you reduce flow area. It is a compromise!
The old speedster motor with an early small chamber Sherman head and an A crank had almost 10:1, I don't remember the chamber volume on that one. Even with a big Gemsa cam it had problems with detonation. I traded heads with Kevin Pharis and brought it down to 8:1 and it ran like all get out. Also tried a z head and it didn't have enough compression to boost the loss of low end from the big cam. Not really touring car stuff but if you go on the Santa Clara Endurance run and want a good donut on Mount Hamilton you need some suds. Funny though, the year my wife and I won the run it had an almost stock motor in the car.