Compression Ratio

Case now bolted up and spent a few minutes tonight measuring deck height, to compare to the confirmed cc'd volume of the heads.

Interesting to see that two measurements are possible, the first with piston rings in and out. 

The latter probably more indicative of the position of the travelling piston as opposed to the static, restrained movement by virtue of the piston ring drag when static.

For clarity piston rings in situ measurement [1], out "free piston movement" [2], [3] shows effect of reducing volume of head to 60cc, and then [4] shows at 55cc.

For safety and longevity don't wish to reduce the deck height any further, as such to increase the compression would need to fly cut the heads. 

CB Performance MINI WEDGE come with a 65cc volume. 

Alternatively increasing cylinder size would have the same effect, but keen to stick with 90.5mm due to longevity etc

Given the "free" piston measurement, and allowing for expansion seems safe to predict a CR of 8:1. 

Engine will run an FK8 cam from engle as such could go higher given the cam duration, 54 degree valve closure, but 8:1 should reduce risk of associated problems that can come with HIGHER CR's.