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.
So what will it do if rebuilt to stock specs with the correct carb? Will I fight pinging and just have to retard the timing a bit? There for not getting everything out of an HO like they were made. Am I just looking at running a higher octane? It's not going to be a daily driver, but I want to take it on a couple of 200 to 300 mile trips and not have to worry about fuel. So for that I'm thinking build it to run on pump gas.
Yes 10:1 will be tough. i have been down this road many times. I would seek out better gasoline if you want to go that route with that compression. You have to be on point with tuning but even then you cant set the timing to where it would be optimal for the engine to run like it should. I would drop it down to 9:1 with custom pistons since there is really no choice with an off the shelf piston.
