so i've read that longer spark plugs can be a bad idea, but also have read they can be good too... The 307's used in the 85-87 442 would require an R46sx ac delco plug, but all i can get are R46SZ plugs at autozone... same plug?? idk...

right now i have Champions in the car (for some stupid reason) and they are longer than the R46SZ's i just bought.

now i know that GM engines usually require Ac Delco plugs. is there anything bad about having a longer plug in this motor? or will it run just as good on the plugs that are shorter?

Any insight on this would help me greatly...

btw it runs a lil rough at idle, and i read that having a longer plug in a motor can cause the exposed threads to act like a glow plug, causing the mixture to fire too early like an overly-advanced spark timing... possible?