I am having a bit of a hard time deciding whether or not my timing is too far adavanced, or if I have a misfiring cylinder. When the car warms up, it feels like it is pinging under heavy acceleration, but retarding the timing seems to only make it sluggish and unresponsive (gutless would be a better word). Otherwise, I am wondering if maybe a plug wire is too close to a header and is grounding out when it gets hot. All seems ok when relatively cold. Does anyone have any suggestions? [350 w/New dist cap & spring kit, new vac advance, and new wires on fresh rebuild with new carb to boot]

Drive the car to warm up the motor and then pull the plugs. Inspect them with a hand held microscope (like 20X or similar). Look for tiny beads of metal on the insulator and plug gap. If you see them you have pinging. The metal beads will be dull grey in color and easy to spot with the microscope.

What compression ratio are you running? What octane of fuel are you using? Are your heads aluminum or iron? Is the pinging isolated to a narrow range of load?

I have seen a circuit someone built which was connected to a knock sensor. The knock sensor was fairly inexpensive. The circuit would illuminate a light and buzz a buzzer when a signal was detected from the sensor. But you have to know how to use it since it isn't filtered like it would have been in the orignal application. Other engine noises like roller timing chains and lifter noise can set it off. But never the less, it does provide a way of hearing engine noise. You'll soon learn what is normal and what is pinging. I'll start hunting for the schematic.

You'll probably have to fool with the mechanical advance mechanism and vacuum advance. Make sure you aren't experiencing a lean condition under accelleration which will contribute to pinging. A step colder on the plugs may be necessary if everything checks out.

BreathWeapon, you've got mail. I have aquired the details on the knock sensor project I mentioned.

Cool, thanks man. I am only running 8.5:1 compression and have tried premium fuel to see if it would help, but still no dice. I may have a lean condition alright, since my jets are pretty small (put them in when it was 30 above C, now it is below 0 C). The thing that leads to to believe it isn't lean, however, is that when the car is cold it seems ok, but when it is hot it starts pinging (or what feels like it). Normally, a hot engine can run leaner than a cold engine.

I suppose there is a chance that either my advance springs or the vac advance unit is failing, so I might poke in there a bit too. With a Moroso spring kit, i just used the silver (stock) springs, do you thin I should go lighter or heavier maybe?

You shouldn't be having problems with pining so I suspect you are correct. It's either really lean, or the timing advance is whacked. I would see where you are in jet size relative to the baseline figures from the manufacturer.

The baseline settings generally work for all applications. Any rejetting would be done to compensate for altitude changes but not temps. The choke will handle the cold mixture.

You want your nominal mixture to be pretty close to the magic 14.7:1 ratio. With EFI, it's a different story. It will lean out the engine at warm cruise at low loads. A carberator isn't smart enough to adjust mixture according to load other than WOT. So don't headge on leaning it out too much.

Check your weight bushings while you are in there peaking at the springs. Shouldn't be rusty. Bushings should hold the weights properly. For example, the old GM HEI ignitions would wear out the weight bushings and allow the ignition to advance as much as 50*.

Interesting. I'll do some more poking when it warms up outside a bit more. The stock Holley jets are #72, and I had to put #67's in it to lean it up for the 3600 altitude and scorching summer heat. #72 is still to rich even in the winter, but I will creep the jets up a bit to maybe #69 and see how it does. The choke has been removed entirely, so no sense going any further on that topic. I will also check the bushings like you suggest, it never occurred to me to inspect them.

Thanks for the tips,
BW.