defiant1

Okay, rebuilt the 2 BBL Q-jet so I was able to move on and set the timing.
BTW: 1970 Stock 350 with Pertronix III Ignitor, new cap, new wires. TH350 with 2.56:1 gears. Unknown if camshaft was changed by PO.

I checked the timing and it was set at 23* @ idle (vacuum advance plugged).

So, I set the timing to the guidance I read here on the forum at 12* @1100 rpm (v.a. plugged). After doing so, the car would stall when going in reverse after engaging the brake. It would also surge/jerk while in drive under 20 mph.

So, I asked around and was told to set my total advance timing to 33* @ 2000 rpm. I did this and it seems to run good. No pinging at highway speed and it does not stall or surge at low speed. The weird thing is, is that at 1100rpm the timing is 23*. ( I did have one instance where the car had a hard time starting when it was warm with the timing set 33*).

Even though the car is running fine. Isn't this too high of setting??

I spent all day trying to find a happy medium with no success. I get pinging at 24* @ 1100 rpm.

I tried 10*, 12*, 14*, & 16* all at 1100 rpm with the same stalling and/or surging at low speeds.

So I guess I need to know if this is indicating that something else is worn or in need of replacement?

Thanks

d1

svnt442

It sounds like the advance curve has been messed with.

defiant1

Okay got an update. I could not get the timing right by myself. So, I took it to the local mechanic. He set the timing by "ear" and feel of the motor. He also discovered that one of my idle mixture screws was screwed to far in, thus restricting air flow and the fuel to air mixture was off. So, this explained the surging and stalling characteristics.

Based on his adjustments I took it for a spin and noticed my low end torque was non existent and there was no pinging. After I got it home, I put a timing light on it and it is set at 6* @ 1100 rpm. I advanced it two degrees (8* @ 1100 rpm) and ran it again. I got my low end back (squawked the tires) and I had no pinging etc.

Sooo, am I pushing my luck if I advance it anymore (let's say to 12* @ 1100 rpm) or is the current setting fine and won't hinder motor performance???

d1

OLD SKL 69

I had the same issue with my Cutlass, no low end torque. I boosted my base timing from 6 up to 12 degrees with no problem, other than I have to run premium. If you do not have any pinging, I wouldn't worry about where your timing is currently set.

compedgemarine

the base timing is of little importance if the mechanical advance and the curve are altered in the distributor. my 68 442 ran with total advance of 36 and never had a detonation issue. the base timing listed for any car is based on a factory set distributor that allows for a total timing that the factory was after.

defiant1

Could you elaborate? I don't understand how the mechanical advance gets altered? Is this something I can control?

How did you set your 36*? What rpm did this equate to?

OLD SKL 69

Mechanical advance gets altered if someone had changed the weight and springs in the distributor. (Under the rotor) They make spring kits that can have more or less tension than the stock springs. This will effect how fast or slow the timing curve kicks in. It allows you to play with your timing curve to maximize power and/or eliminate pinging.

compedgemarine

every dist. that is not locked in (has no mechanical adv.) has weights and springs that move to increase the advance as the RPM increases. the factory set the dist up differently for every engine, car combination. there is a stop pin on the bottom of the weight plate that stops the plate as it advances and the springs change the RPM and rate they advance. my 442 was set up so the advance was all in by 2600 RPM and had 24 degrees of mechanical advance. I never had the vacume advance hooked up on mine. vacume advance was actually created by the factories to help meet emissions problems that the government hit them with. the TCS solinoid was part of that, it advanced the timing in high gear to reduce emissions and increase MPG. if you do not know all the history of the car it is possible that the distributor is from a different model or year or someone may have changed the springs. the stop pin could be worn out allowing the advance amount to be too high. I use a advancing timing light and check the timing all the way up till the mechanical advance is all in so I know the base and total.

compedgemarine

sorry for the same info- SKL 69 typed faster than me

defiant1

Thank you gentlemen. Those were great explanations. I know my timing stops advancing at 3200 rpm. I guess I will need someone else to help me with this so I can figure out the total advance. My digital timing light allows me to figure out the degrees, but I think I will need someone to hold the rpm at 3200 while I focus on the timing light and tab to get the correct reading.

Thanks again.

d1

88 coupe

Subtract the advance at idle from the advance at 3500. The difference is your distributor advance. If you have 30° at 3500 you can move your initial up 3° to get 33° total.

Leave the vacuum advance plugged until you have the distributor (mechanical/centrifugal) like you want it.


If there were government mandated emissions standards during the thirties, that would be a possibility. But the first emission standards (other than the earlier PCV systems) in California, were not in place until '66.

Perhaps you were thinking of the ported vacuum systems that replaced "full manifold" vacuum in the seventies (or was it the sixties?) to meet the emissions standards of the day.

Either way, it is another internet myth. Both "manifold" and "ported" vacuum advance have been in use since the thirties, if not earlier.

Norm