Base Timing Questions

I ran across the same issue with timing my car (340,unknown agressive cam). I'm not a pro but I used the old school method of using a vacuum gauge for highest reading at manifold vacuum with the advance can disabled. Once I found highest vacuum (10hg) I backed the distributor back a touch. I put premium gas in it and watched for pinging under load and hard acceleration and backed off timing a touch. I then adjusted the vacuum can. I did not use a timing light at all, I gave the car what it wanted, the distributor already had a performance curve. Keep in mind that I started with a running engine that just needed timing and carb tuning.