Datsun Roadster Forum-311s.org

A simple cold compression test can point out cam timing too. Or just the first pump as the intake valve is open on the compression stroke

If you recurved the distributor as mentioned previously, 20° is no problem. If the mechanical advance is not working then you’re not getting any additional advance as you accelerate. If advancing the timing made it run better that may be the issue, or at least part of it.