Hoping the brain trust can give me some insight on a problem I have been trying to solve for 20+ years. I have a 440 I in my truck that I put together quit awhile ago. It doesn't get driven a lot but its my time and money pit since the mid 1980 when I bought it. The specs: early 1970's 440, 906 heads, comp cam 270H grind. performer intake, Holley 770 street avenger. Heavy 4WD truck. 37" tires, 4.10 gears. 4spd. Runs great at WOT or any high rpm's for that matter. Its the low rpm that I get detonation knock. I slow to turn a corner and get off the gas, then back on it it will ping. Once I up the rpm's its fine. From a slow cruise to on it, it pings if I don't immediately down shift. On the highway at 60mph and I get on it's fine. I have always figured to much compression, not enough cam. I wanted 9.5 to 1. Not sure where it ended up.
Now that I am old and just want to cruise around when I drive it, and its more of an issue now. Working on its tune recently I took a look at its distributor curve. I took some readings at idle though 2800rpm and something doesn't seem right. All the mech advance timing is "in" at 1800 rpm. So I purchased a set of Mr Gasket advance springs. I was going to just start swapping them in and see what happens but I thought there may be a know good working spring set that I could start with? Thanks in advance for any info or insight.