Thanks for the tips. Sounds like I'm going to have to really pick the brain of the engine builder and get his thought also. He got the shop from his dad and has a long time following from the Pontiac crowd. When I first approached him about the 350HO and explained that I just wanted to refresh it and keep it stock, he commented I could do that, but I would really have to watch my tune. Didn't ask for clarification at the time. I got really excited when I was doing the research and found that I had a 350HO with #48 heads. Factory 325HP with no build, COOL. Now I'm coming to the conclusion that I can't really run that engine on todays gas. Or I can, with a bunch of modifications. Hardened valve seats, Lower comp pistons, different cam. Then its not really a 350 HO then is it? I got all summer to decide..........
You could try an octane additive or aviation gas if you have a small airport locally. The problem with retarding timing to compensate for the pinging is that it greatly effects engine performance and just adds heat to the exhaust so the engine will run hotter. But you really need to figure out what the actual compression ratio is. you really need to know the exact CC of the combustion chambers of the heads, the piston the deck clearance, the volume of the valve re leafs in the pistons and the thickness of the head gasket. some of these cylinder heads did not have the supposed combustion chamber size. Not all 72 cc heads had a 72 cc chamber. If you have a set of the #48 350 HO heads, those chambers were supposedly 68cc chambers. But you never know. Back many years ago when we had good gasoline we would run Sunoco 93 in these engines without any problems.
