Too much timing

[lukecp]

I was out cruising around in my truck today, and i noiticed a little spark knock while pulling a hill. So, i stopped and backed off the vaccum advance timing (Crane adj. vaccum advance) about 3 degrees.

And wow!! The truck runs alot better with less timing! Throttle response, midrange power, and idle quality all impoved. It even seems that the full throttle power increased too, but i hadn't gotten into the 4bbl in awhile so it's hard to say.

I was kinda under the impression that an engine usually runs best with the timing advanced as much as it saftely can be w/o pinging. It usually dosen't ping, i just had filled up with a tank of cheap 91 octane fuel (proably the problem).

I am running 11 degrees of base timing on a stock HEI, the Crane blue and silver mech. advance springs, .045" gapped plugs, and 9.7:1 compression with a 204/214 cam.

Is there an easier way to figure out the ideal timing for my engine than the "seat of the pants" method?

[70c10]

This is a nice link. http://www.73-87.com/garage/hei.htm

[crazy longhorn]

the best way is to experiment a bit. I use a timing tape, & try to shoot for a 34-36 degree total, all in around 2800. An additional 10-12 degrees on the vac can should be pretty close. Your comp ratio, coupled with a fairly mild cam may be why it likes a little less timing. Good luck,crazyL