talked to engine builder today, rings in both cylinders 2 and 3 were broken so would explain loss of compression as well as head not properly flat. Found it also has teflon bushes in the gudgeon pins instead of using circlips, supposed to remove friction and allow the pins to rotate easier or something, pretty cool all the little things that have been done to the motor. Also got double valve springs from kelfords and another motor which had an a3 cam which will be going into the rebuilt motor, good for 8000rpm. The other motor has some fancy bits in it too but it will wait until the current motor has finally died before rebuilding that