The P 35 cylinders are unique to the motor, the P 40 and the early PR 40 are bushing motors, The later PR 40 and P 45 or roller bearing motors and have higher compression due to the cylinder heads being padded inside and the timing is different, it’s my understanding that they all use the same carburetor but I could be wrong again all mine my P 35, 3) P40s , and 3) PR 40s all have the same “P35” carburetor i’m not sure if there’s any differences , as for my 2) P 30s have a different carburetor, I do not own a P 45… Yet. Needless to say they are all cool motors and not common, get it running and enjoy it and then pass it on to someone else who will enjoy it …. as far as the compression relief goes I believe it came out in 1929 I have a PR with a compression release cylinder not sure if they came standard on the P 40 but I heard it was an available upgrade 🤔
Rotary valve Johnson’s Rule!
