I just put a modified points type dis. back in my car. I origionaly had an HEI in the engine since I rebuilt the engine a month ago. I have a 350 with 10.1 to 1 compression. (This is actual compression not a guess.) A T/A 212 cam, Q-jet 800 cfm carb, stock exhast manifolds, and what I've discovered to be a 1700 stall converter. What I really can't figure out is do I want to set the timing for what I think will make the most power and then adjust the carb to eliminate pinging? Or do I set the timing some what retarded from what I think will work best and try to make some pwr from the carb? I've been running the car with out the vacume advance hooked up and the dis. set to 20 initial and 33 total. I get a bit of pinging when I try to step on the gas. cruse idle seems to be fine. I'm getting low to high 15 mpg. What can I do? Any help would be appreciated. Thanks
The carb and mixture settings should not affect detonation/spark knock unless you are running way lean. Set the timing to eliminate spark knock and work from there. Maybe your advance is coming in too quick and that, combined with low vacuum signal and the big carb, is giving you a combination of lean mixture and too much advance when you punch it at low speed. You shouldn't need the have the Q-Jet air door adjusted really loose - if you feel the secondaries "kick in" you're probably getting a lean bog when they open. You'll need at least 92-93 octane premium with that compression -forget about 87 octane gas. Also, make sure that your cooling system is full and that the engine is running at optimum temps. If you run the coolant low, the heads will not cool properly and you'll get preignition and noise.
Hey John thanks for the reply. I just took the car in yesterday and put it on a gas analyzer. The idle mixture was a bit lean and the vac. adv. which was hooked up to the manifold vacume was making hydrocarbons like it was the only task it had to perform. I switched the vacume back to ported and lowered the primary metering rod heighth so I would get a 2.5% co mixture at 2500 rpm. Things look really good on the gas meter now and my timing is 13 initial with 10 mechanical deg. and 10 vac. deg. for a total of 33 all in pretty early. I'm going to switch the springs in the dis. for heavier ones today and I hope to get rid of the last bit of pinging I get when I'm crusing at 1700 to 1900 rpm and just barely step on the gas.
