Heads going to be around 40cc

77.1 stroke, 91mm bore

0.75mm piston to head clearance

so with a 15cc piston bowl I make it 9.3:1, 10cc bowl 10.0:1, 8cc bowl 10.4:1

By machining the tops of the pistons A crown to 1st ring height of 7mm gives a bowl CC of ~13.8

6mm = ~10.2 CC

5mm = ~7.0 CC

So if its ok to take that much off the top of the piston and plane the block to give a sutable head / piston clearance then a CR of 10+ is feasable.


Any comments?