Now we are getting somewhere. Put the stock HEI weights back in. 25 degrees is too much advance. They are probably advancing the timing too soon in the lower rpm. The stock weights are supposed to be 20 degrees. If they look worn at the pivot holes, replace them with some new stock ones or some good used ones. Also, check the pins to see if they are worn.
With the stock weights (20 degrees) and initial advance of 10 to 12 degrees it may be OK. The two blue springs should work just fine. This is what I have been running in mine. I plan on trying a blue and silver to see how I like it. A silver would probably be too much for you.
Try the stock weights and maybe lower the initial a little and see what happens.
Also, you might try richening up the carb a little. If it running lean, it will ping like crazy. 600 CFM is on the low side for this beast. You could run a 750 with no problems and would really make it come alive.
One more suggestion if I may. The first thing I would do is replace the distributor with a MSD Pro-Billet HEI. Of course they are not cheap, but you get what you pay for.
The second thing is get rid of the Jacobs crap. I had a Jacobs Omni-Magnum on my truck. I got tired of it messing up on me and took it off. I used to think Jacobs was good stuff, but I found out the hard way. From now on it's MSD for me.
Just my $.02
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Mike
1985 Chevy C-10
Mike's 73-87 Chevy Pickup Site
[This message has been edited by swervin ervin (edited 12-27-2000).]