I don't know what you mean by "what would be a good rpm for this motor".If you mean a good rpm for setting, just move the dist slowly opposite direction of rotation to advance until the engine seems to be running easier--it will get faster idle in the process so you may have to slow it down and continue.When it has been advanced until it is starting to get rough you have gone too far--but we are trying to prove that your "timing to book at 7 1/2 BTC" is not correct, there could be several reasons for error, but tell us how it reacts to advancing the spark timing until it sounds "happy" and we cn go from there.
Just one step at a time please.
