Don't know if you have found your answer yet. But had the same issues with a .030 over 398. It sucks - I know. Debated most of the solutions listed here... tried a few, as well.
I was told - the vacuum advance was primarily to promote better gas milage, and that the car would run fine (although Lopey ) without it.
I disconnected the advance & drove the car like this for another year. While this DID NOT totally eliminate the mid throttle pinging - it did reduce it greatly. If you are running a quadrajet - also look into the setup of the rods - a little extra fuel at mid throttle, while a band-aid, can help too.
The best solution - as stated earlier, is to reduce compression.
A set of 6x heads would be easy to come by, flow pretty well stock, and can be modded to flow like crazy. The next step up would be 96 - these are a little more desireable ($400-500) because they have the larger exhaust valves.
I was lucky enough to pick my 96's for $150 - added hardened seats & new valves for a total investment of less than half the price of the edelbrocks....
BTW the edelbrocks are around 87cc
Check out the Q&A on CLASSICALPONTIAC.COM - lots of compression talk going on there - from all the guys building 455's.
Good luck!
Chuck
I was told - the vacuum advance was primarily to promote better gas milage, and that the car would run fine (although Lopey ) without it.
I disconnected the advance & drove the car like this for another year. While this DID NOT totally eliminate the mid throttle pinging - it did reduce it greatly. If you are running a quadrajet - also look into the setup of the rods - a little extra fuel at mid throttle, while a band-aid, can help too.
The best solution - as stated earlier, is to reduce compression.
A set of 6x heads would be easy to come by, flow pretty well stock, and can be modded to flow like crazy. The next step up would be 96 - these are a little more desireable ($400-500) because they have the larger exhaust valves.
I was lucky enough to pick my 96's for $150 - added hardened seats & new valves for a total investment of less than half the price of the edelbrocks....
BTW the edelbrocks are around 87cc
Check out the Q&A on CLASSICALPONTIAC.COM - lots of compression talk going on there - from all the guys building 455's.
Good luck!
Chuck