- Apr 21, 2022
- Reaction score
- My Car
- 73 Mustang convertible
I've started the low idle adjusting needles at being backed out from the seat by 1 turn and went to 2-1/2 turns. At 1-1/4 turns out I got 19" at a fast idle (choke hadn't pulled off yet, when it idled down the reading went to 16". Coil voltage was about 10.7v. 16-17" of vac is the best I've gotten at low idle.To get an RPM reading get a timing light that includes RPM readouts. A 'dial back' timing light is the best choice, you can adjust the flash of the timing light to the current TDC to see your current timing and then set a value of advance that you want and adjust the timing to that value. They are super handy.
16 inches is 'pretty good' vacuum but not as high as I would think you can get with a relatively stock 351C 2v car with a 2bbl carb.
Have you adjusted the idle mixture to 'best vacuum'?
The 10.6 was with the engine idling, the voltage is a little over 5 with key in the on position, engine off.I've watched the choke/ fast idle pull off move as the engine warms.
The voltage at the terminals on the Pertronix is running at 10.6v (+/- a few tenths due to readout of the digital VOM bouncing a little). Isn't there a dropping resistor on some systems?
Thanks for the explanation. I understand now.You have to bypass the stock coil wire (red with green stripe) by running a new wire or splicing a new wire in place of the resistor part of the wire. If you trace the wire out of the ignition switch you can tell when the resistor starts because the wire gets fatter. Not easy to see in those tight areas so pack your patients and maybe pull out the drivers seat if you end up spending time on your back.
If you have a 72 or 73 you can use Circuit #640, which is a Red Wire with a Yellow Hash tracer. It is used to power the Throttle Position Solenoid (TPS), and has enough switched current to power the Pertronix ignition coil.I'm measuring 10.3v at both small terminals on the Pertronix. How do I bypass the internal resistor?