MTFCA Forum

Replaced pistons/rings. Now have engine knock when advancing engine timing. Quiet at idle, noise increases when advancing Distributor with advance lever and increasing rpms.

did you check the cylinder taper with a gauge?

no I didn't....Thank you for advice.

It could be knocking from having overadvanced timing,,, kind of a low distinctively hollow thumpy sound. Especially noticable when running off a battery / distributor system. Some dizzys can way overadvance your motor - we had a delco in the '15 roadster that was miserable for this - and it was a short distance from retarded for starting to overadvanced.

Also... When you crank start your car (with the spark lever fully up) does your car have a tendency to want to "jerk" back in your hand? that's a sign your spark lever adjustment (or rod length) may be incorrect for your distributor, and you never come off BTDC.

When you tighten the cylinder up with a piston/ring replacement you will increase compression, (providing the cylinder is round) and put more strain on the lower end (rod journals). If the the rod or main bearings are marginal the increased compression will cause any bottom end wear to be amplified and you may notice a thump that wasnt there before. And advancing timing will effect this even more as ignition occures further BTDC. I will also add that valve seal will play a part in this also. Might get some plastiguage and check crank bearing clearance.
Saying this based on no mention of the crank/bearings condition in the original post.