Restoring a 1968 Morris Cooper S and wondering what piston compression ratio is best these days.
Let me say first this project started in 1994.
I'm almost complete and now having some second thoughts on the pistons I have used.
I decided some 15 years ago when rebuilding the motor to go with Hepolite 8.8:1cr pistons.
At top dead center they are a good 0.2" below the top of the block deck.
The block was bored to + 60thou (had a seized piston), the head was faced and the block deck faced.
My reasoning at the time was with the increase in swept volume with +60thou pistons, head faced and block faced the compression ratio would be near 9.1:1CR and given fuel octain was a max of 95 at that time.
Interested to hear from others if this was a good idea or; should I replace the pistons with 9.75:1cr?
How much will the reduced compression ratio affect the performance?
The motor is pretty standard otherwise, 1.25" twin SU, Maniflow Cooper Freeflow manifold and RC40, 510 Cam, Aldon distributor.
Ian
