[Drivin' Miss Daisy]

Joe,

I know that you say that your timing is set correctly. Where is it set at? In my 1985 w/305 I can't run it where the factory recommends. I have to retard it slightly. Also Dave is wrong about gasoline. I was an octane technician for an independent test lab for 13 years. All gasolines are blended with the same base components to achieve the minimum octane rating. And the gasoline that you buy at Shell for example might be from the same company that blended the gasoline for the Sunoco station up the road. The detergents in the fuel have no bearing on the actual octane value of the fuel and detergents in the gasoline really are predominantly there to help keep fuel injection systems clean, not really relevant for an old carbed vehicle. There is a difference however in the fuel we use today and the fuel that was produced when our trucks were built. I find that midgrade fuel today is closer to what 87 was in the eighties as far as performance goes but is still a completely different use of components.

You might want to try retarding your timing slighlty and use midgrade octane gasoline. On my truck the factory label states 4 deg., I run mine at 2 deg. on midgrade and have gotten rid of the pinging. I started off by retarding it to 0 deg. to see if it helped and then advanced it from there until I found my sweet spot, which for me is 2 degrees. At 0 deg. I can run 87 octane with no ping, but I prefer 2 with 89.

Hope this helps some and let us know if it works for you.
Darryl