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.
I'm slowly getting the wife warmed up to the idea of doing the HO motor. Should hit the paint booth this week or next and I'm putting HO stripes on the side, so I kind of HAVE to put the HO in. Not looking to build a race car, but I would like to just do a "to spec" HO 350. I got to thinking, will I have any problem on pump gas with 10 to 1 compression? The gas we have now is way different.
This Mike Noun site discusses Royal Pontiac's modifications with about the most detail I have seen. However, to be sure, you should try to locate the original Royal paperwork to verify if and what was done.
Hello. I picked up a Firebird last year. Ordered documents from Pontiac Historical. Guy told me this was a special car. It seems I have found a bobcat. I’ve hit a wall trying to find out what mods were actually done to the car after it was received at Royal. It was delivered with a 350ho and a 3 speed. At this point I own a shell that was stripped and an interior that mice lived in. Maybe someone here can point me in the right direction of who I could contact to find out what this car would have after the dealer worked their magic.
