Chevy 350 timing?

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!

TIMING FIRST

1. Is the vacuum advance disconnected? Is it connected to the correct port on the carb? You do not want a buch of vacuum advance at idle.

2. On a '79 Corvette the #1 plug wire goes to the first post clockwise from the wire extension when looking at the distrubitor from the top. Is that where your's is? That provides clearance to move the vacuum can away from the top of the manifold.

3. Is your mechanical advance working?

4. Set your timing to about 12 degrees before top dead center as a start.

When these issues are addressed take the car out of another trial run and see if all or any of your problems still exsist.

Sounds like you need to pull the distributor out, turn the oil pump shaft to point where you need- and then re-insert the distrib so that you have more room to turn it before the vacume advance hits the intake.

After advancing it some more- if it still doesn't run quite right- there is still no need to replace it- just get it set right.

Call around to some engine shops and find out if there is a place near you with a distributor curve machine- you'd take them your distributor and they can setup a custom advance curve matched to your engines specs. Shouldn't cost anything near what a new distributor would....

Just pulling and re-installing for more room though should give you a few more degrees of inital timing- that alone may make all the difference you need! Give it a try!

There is one more thing yo ushould take a look at. You said, besides the intake/carb stuff, everything else is stock. You got a lot of fuel/air going into the engine. You should definately look at getting some headers and around a 2 1/2" exhaust to let the engine breathe.