I have a stock 430 in my '69 Riviera. It doesn't seem to like any brand of pump premium or octane boost. I always have to use Sunoco 110 (about 3 gallons to a tankfull) with pump premium. I doubt there are any timing or dwell problems because the engine idles, accelerates, starts great. Does anyone else manage to run on the normal pump premiums? Is there a trick to make the engine run on this without spark knock?
I have the same problem with my 350... except we don't have any 110 pumps around so I just detune my timing, run 93 octane, and use octane boost... helps, but doesn't eliminate it.
Spark knock Carbon in the motor can cause pre-ignition through hot spots - the carbon stays hot enough to cause the fuel to ignite early. There are a bunch of folk remedies for this, but the favorite is just beating on the car to "blow the carbon out". Some guys rev the motor and dump automatic transmission fluid in the carb, or water, or I don't know what else. Excessive oil in the cylinders will cause detonation - bad rings, valve seals, or poor sealing at the intake manifold can cause this. Also, make sure your cooling system is up to speed. Especially if you run your radiator low, the cylinder heads will run hot and encourage detonation. Check your ignition advance - the bushing that limits the weights in the distributor is plastic and famous for disintegrating - you will end up with way too much mechanical advance, like 50 degrees or so. You shouldn't have more than about 32 degrees total mechanical to get by with pump premium.
Thanks John, I was actually going to try the (steam clean) water down the carb trick. I don't have a problem with oil consumption but you brought up a good point about the cooling too. I'll check that. My car has 83,000 on the original motor that has lived a soft life. Truly was owned by a little old lady. Well, she wasn't in Dec. 1968 when the car was new but..... I'll post if I see results.
