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
Got to a rural general aviation airport and squirt in a bit of 100ll av-gas. Pinging will stop. Jim Lore
and motor will blow up... aviation gas has too much oxygen.... seriously tho, turn down the timing. Get the power from the carb... Set the carb for optimal air/fuel mix, and set the timing to just under what it will ping at. 20 sounds a bit high, expecially for that much compression... I'd guess around 14 or so... maybe start at 12, then go up 2 degrees at a time and when pinging starts, back it down. just remember when summer hits, it may need to be turned down a bit
I am running about the same setup, except I just put an HEi in mine from a points system. I have my timing at 18*-20* and total 32*. I got it down to where it will not ping unless it's very hot outside. Richen up the carb a bit and it should get you there. If that doesn't work out, try a little octane booster. there used to be a product called "Knock Out" that I had great luck with. I have since just been putting a few gallons of 110 octane in with the 91 Premium unleaded, if I want that little extra kick. What plugs are you running? You might try the equivilent of an AC R43TS or R44TS instead of the R45ts. Mike
Thanks for the responses every one. I guess I should have given a little more information. I live in Salt Lake City Utah. The elevation here is about 4500 ft. I would normally set the timing to around 13* at sea level but with the dif. in altitude I have to go a lot higher then 13 to get the rear tires to break loose on a pwr break. The dis. has a pertronix module in it and I went to that because the HEI was just to big for the 350. I always had to take the cap off just to try and adjust the timing. Kind of hit or miss if you know what I mean. I want to use the vacume advance for better fuel acconomy. I have been running it with out the vacume advance and when I hooked it up I got 16.5 mpg. on the last tank. That was the only change I made and I have been getting on it more than I normally do. I have reset the timing to 10* mechanical and with the vac. adv. plugged in I get another 10*(I have a limiter on the vac. canister.). That puts me right at 20* to 21* of initional timing. It jumps around a bit but I don't know if that is because the carb isn't set right. The rest of the timing comes in as soon as you touch the gas. Probably close to another 10* right off the batt. Maybe I need to go to heavier springs. That gives me about 30* by 1300 rpm. The last few deg. come in by about 2200 rpm. Now I know sence I'm using manifold vacume instead of ported vacume that I loose some timing right from the point I step on the gas but I have checked and it's only a couple of degrees. The mechanical adv. kicks in so fast the engine doesn't stumble at all. Mike I don't know what the number on my plugs is but I will check. They are autolite plugs which I prefer to the AC plugs for the electrode sticking further into the cumbustion chamber. I have a new set of taylor wires that I put on when I rebuilt the engine which now has 3100 miles on it. Not to bad in a month. Of course the trip to Vegas for the buick drags helped. No better way to break in a motor than on the Track I say.:grin: Especially when you have people like Jim from PAE to help you tune things. I really don't want to go the route of putting racing fule in the tank every time I fill it up. I don't mind putting it in when I go to the track but It's to much of a straign on my pocket to do it all the time and I don't know of any place around here to get racing fule. I used to have my carb set up for 2.5% on the hydrocarbons which I was told was the right mixture at 2500 rpm to produce the most pwr. with out being to lean. Does any one have any other suggestions? Right now I have no idea what it's set up at since I haven't changed any thing after I put new jets (73s) in the primaries and reinstalled the metering rods after much needed cleaning. They were sticking from dirt that had got in the carb while it was sitting on the bench waiting for my engine to get finnished. Let me know what you guys think.
Jason ole racin' buddy, Definitely try a colder plug. I run 42TS in my 455. Make sure you're not lean at the carb, that will always cause detonation. How's the temp on a warm day? Higher at cruise than around town? You should also get that vacuum advance to ported vacuum or it will be at maximum all the time (except WOT). Get a curve kit at any parts store and shoot for a little slower advance. I'm not sure what the recommended curve is for the 350 but the 455 likes it all in about 2000-2500rpm... 1300 is way too soon I would think, and might contribute to the ping. Now, if I'm full of prunes guys, let Jason know so he doesn't take half-:moonu: advise.
