1975 Chevy Nova set timing

you will need to use a timing light. Disconnect the vacuum advance on the distributor and plug line. on the cover of the harmonic balancer and cover there are two timing marks. clean them . hooking a timing light to number 1 cylinder. Before Loosen the distributor cap . {Make sure you mark original location of the distributor} I have seen it where someone had moved the distributor and did not know where the original setting was. start engine and point timing light to timing mark on cover. Move the distributor a little at a time tuntil the two marks line up. retighten the distributor.