Types of 7M valves & comb. chamber volume

[BLACKCAT]

How many different types of valves are there for the 7M & how much of a difference would their shape make to the compression ratio?

Can you determine the compression ratio of the 7M by measuring the combustion chamber volume, which is around 39cc for the spare head I have in front of me, & what is the formula?

 

[gofastgeorge]

The formula is:
Cylinder displacement + comb ch vol
combustion chamber volume

And don't forget to add the head gasket volume & the piston dish volume to the head volume to get the total combustion chamber volume.

As in my case with Wiseco pistons:
cyl v 498cc + head v 41cc + pis v 6cc + head G v 8cc
Comb c v 55cc

So my ratio is 10.05:1

 

[amichie]

I measured mine today and it has valves like the left pic. It came to 43cc with a stock spark plug fitted and original head thickness of 116mm.

Edit: I remeasured it a couple more times and its 42cc.
I also meausred the piston dish of an old NA piston and it is 11cc.