I have a 1967 Firebird with a 1979 Chevy Corvett 350 L82 engine and I can't seem to get the timing to adjust very good. I have a HEI distributor (don't know what it came out of) with vacum advance, a Edlebrock 650 carb, and a Weiand intake, the rest is stock. The problems I have are pre-ignition sometimes, hard starting when hot, and lack of performance. The distributor has to be adjusted all the way forward to the point where the vacum adv. hits the intake and that is where it runs the best. I was thinking about buying a new dristributor from someone like Summit but I don't want to spend hundreds of dollars and find out I wasted my money. Any ideas will be greatly appriciated!