Pertronix 1181 stock 72 350
 

In the process of installing a pertronix 1181 in a stock 72 350. Directions mention with or without ballast resistor. I don’t see a ballast resistor. Believe it has a resistance wire instead. Would I just wire up as if it doesn’t have a ballast? Also has a condenser on the points set, but also another on the coil bracket. Would I keep this or eliminate it. Lastly has a stock 293 coil. Am I ok to keep using that?

Re: Pertronix 1181 stock 72 350
 

I've had a 1181 set on my Chevelle for 25 years and have never had a problem. Car has a resistor wire. The point set goes away entirely (kind of the whole point of the Pertronix set up). Keep the condenser on the coil, helps keep radio buzz from happening. Be sure to shim the distributor shaft per the instructions if the distributor is worn and has a lot if up and down movement on the shaft.

Re: Pertronix 1181 stock 72 350
 

Minimal up and down movement. Clearance for module to ring is in spec .010-.060. Did test the vacuum advance and it doesn’t hold vacuum or move at all. I’ve ordered a new one, but the truck runs fine so do I really need it working?

Re: Pertronix 1181 stock 72 350
 

The Pertronix will work fine with the factory coil and ballast resistor. You just need to supply it with 12v.

If you refer to fig 3 in the instructions it shows positive 12v power to the unit being hooked to the ignition switch side of the ballast resistor. We have a ballast wire instead of a resistor. Hooking the unit to the ballast wire will only provide it 8-9 volts which isn't enough for the unit to operate properly.

This means you will need to find a different 12v positive supply from the ignition switch. That provides power in the run and start positions from the ignition switch.

Or hook the 12v positive supply to the Pertronix to the ballast wire where it exits the connector on the firewall.

Or remove the ballast wire and replace it with regular wire and replace the factory coil with one that works without any ballast wire or resistor. And hook the unit to the 12v supply at the coil. That is how mine is hooked up on my Burban.

Re: Pertronix 1181 stock 72 350
 

The vacuum advance not working is going to make your fuel mileage suffer as well as give you a small vacuum leak.

Re: Pertronix 1181 stock 72 350
 

Would that not be the same as hooking the Pertronix red wire directly to the + side of the coil?

Re: Pertronix 1181 stock 72 350
 

The black wire on the 1181 connects to the negative (-) terminal on the coil.

Don't connect the red wire to the positive side of the coil as this terminal is powered via a resistor wire and supplies reduced voltage to the coil.

The red wire needs a full switched 12V ignition source. The pink wire on the fuse panel is a great place to power up the 1181.

The reduced voltage is fine for the coil but the 1181 module needs a full 12V.

https://www.567chevyclub.com/images/C10/Fuse-Panel.jpg

Re: Pertronix 1181 stock 72 350
 

No. The ballast wire acts as a resistor and causes the voltage to drop down to the 8-9 volt range which is too low for the Pertronix.

To see this check the voltage at the positive terminal of the oil when the engine is running.

The ballast wire on our trucks starts at the firewall terminal and goes to the coil. It is the cloth sheathed wire pointed out in the photo.

Re: Pertronix 1181 stock 72 350
 

Great thanks pics help! If I switch out to a flame thrower coil, would that change anything as far as the current stock wiring setup or would I wire it up the same way as the stock coil with the factory wiring including the resistor wire? I would like to do this without hacking any of the original wiring.

Re: Pertronix 1181 stock 72 350
 

The large pink wire that runs to the idle stop solenoid is also a good switched 12V source.

Re: Pertronix 1181 stock 72 350
 

The 1181 requires between 1.5Ω to 4.5Ω on the primary ignition circuit.

The stock resistor wire on my truck has a value of 2.5Ω plus a 2Ω coil for a total of 4.5Ω.

As long as your aftermarket coil is equal to or less than 2Ω it will work well with the resistor wire.

Re: Pertronix 1181 stock 72 350
 

The resistance in the wire supplying voltage to the distributor changes with length. I cut the resistance about an inch long at the firewall plug and soldered a wire to it. Everything stays the same that way, including the factory fusing and switching. I couldn't even measure the voltage drop that way.
When I change to an HEI I do the power supply the same way. It has worked out well over the years.
Cheers

Re: Pertronix 1181 stock 72 350
 

For those of you keeping score at home....

Re: Pertronix 1181 stock 72 350
 

I have that pink wire but mine doesn't have an extra wire or plug like the one in the picture. There is nothing plugged in under that wire on mine where the more red wire is plugged in underneath the pink wire, in the picture, Could I just attach there?

Re: Pertronix 1181 stock 72 350
 

Yes, that empty terminal will work fine. On my truck that terminal supplies switched ignition power to the idle stop solenoid on the Quadrajet carburetor.

Re: Pertronix 1181 stock 72 350
 

Shooting from the hip I don't remember if that is powered when the ignition switch is in the start position. It's easy to check with a test light before you start wiring.

Re: Pertronix 1181 stock 72 350
 

Bingo. I've had my 1181 connected to a resistor wire for 25 years and have never had a problem.

To the OP: Yes, you need a properly functioning vacuum advance. Two additional comments on vacuum advance: 1. Works best connected to manifold vacuum instead of ported vacuum and 2. Not all vacuum cans are the same, make sure you get the proper one for your particular application. Depends on the vacuum signal your engine makes at idle and full throttle.

Re: Pertronix 1181 stock 72 350
 

The aftermarket coil would be a flamethrower coil. The factory coil on mine is a Delco 293. Could I use either one and wire up just like factory with resistor wire in tact?

As far as the module itself I plan to wire it either to the vacant post on my fuse panel in the picture or to the idle stop solenoid.

Re: Pertronix 1181 stock 72 350
 

You can use the Flamethrower coil only if the primary resistance is the same as your Delco. Flamethrower coils come in many different varieties for different applications.

Some OE manufacturers used different coils for 4 or 6 or 8 cylinder engines. They would vary the resistance of the coil to match the needs of the vehicle. Where other manufacturers varied the ballast resistor (or wire) to match the engine and used a single coil for all engine variations in the model.

And many people have swapped coils from engine to engine without taking note of this only to have an ignition failure down the line and never realizing why.

https://pertronixbrands.com/collecti...kjSYa1HoSAAPoX

Re: Pertronix 1181 stock 72 350
 

Would I still use the yellow wire on the coil + side as well as the 12v wire from the fuse panel? Would it be better to wire that directly to the module or directly to the coil then run from that post to the module?

Re: Pertronix 1181 stock 72 350
 

If you're going to keep the Ballast Wire then yes, you need to leave the yellow wire hooked to the coil. The yellow wire comes from the starter solenoid and provides power to the coil only when the starter is engaged. See link and diagram in post 3

If the voltage to the coil is reduced by the ballast wire to 8-9 volts with 12.5 to 13.5 volts (at the fuse box) when the engine is running. But when the starter is turning the engine the voltage at the coil will drop to 6-7 volts which may not be enough to start the engine.

To solve this problem the OE's added a wire from the solenoid that supplied voltage to the coil bypassing the Ballast wire/resistor. This would be the yellow wire on our trucks.

https://67-72chevytrucks.com/vboard/...d.php?t=389516

Re: Pertronix 1181 stock 72 350
 

A little ot but maybe good time to open a discussion on this point.
Regarding point one, why do you want full vacumm advance at idle?
Ported vacuum is shrouded from vacuum in the idle position. When you crack open the throttle plate the ported vacuum now sees intake vacuum. Depending on the load and plate position, could see near zero vacuum until the load drops and then vacuum begins to climb. With static timing adjusted correctly for idel, how does the non ported vacuum improve things? Don't you want a smooth vacuum curve off idea as vacuum climbs? What am I missing?

Re: Pertronix 1181 stock 72 350
 

This is a hot debated topic across many forums on the interweb. There are many variables that contribute to why one way works better than the other on any particular engine. With many people offering their theories as to why their way is the only way. There will never be a consensus on the subject.

You are correct in your statement, if you have a relatively stock engine that has a correctly tuned carburetor and distributor. Once you depart from those parameters then having more timing at idle may be helpful with improving idle quality.

Both methods of supplying the vacuum have been used by OE manufacturers all the back to the beginning of cars. In every case a factory engineer(s) had a good reason to do what they did.

Re: Pertronix 1181 stock 72 350
 

Start by reading the entirety of post #2:

https://www.chevelles.com/threads/ig...6#post-1461956

Re: Pertronix 1181 stock 72 350
 

Yes, debated.

Perhaps this is too simple, but I do have a simplified view of vacuum advance. Who knows perhaps I'm just wrong and somebody will chime in and say so.

The point of vacuum advance is not to provide "more advance. " It is to provide a way to retard the ignition when the engine is under heavy load so you won't get detonation. Goal is with the vacuum advance hooked up and fully actuated, set the timing such that your engine is most efficient. Under low-load conditions such as causal cruising and idling you would want the engine to be as efficient as possible, and that would mean ignition advanced as much as possible, so you burn as much of the fuel as possible in the cylinder before you exhaust it into the tailpipe where any unburned fuel is thrown away.

You will notice if you use manifold vacuum and the engine is idling, when you disconnect the hose going to the distributor and plug the vacuum source, you retard the spark and the idle decreases. That decrease in idle is your engine losing efficiency and your fuel is not igniting as early in the cycle as it could, and you're throwing unburned fuel out the exhaust. You could turn up your idle screw and connect the distributor to ported vacuum and all would be "normal", but you would continue to just exhaust unburnt fuel.

I want the smoothest idle, so I use whichever vacuum source give me that. People here on the forum have said different engines may idle better with distributor connected to ported vacuum and others may idle better connected to ported vacuum. I won't tell you what my engine likes because I'm sure it's hooked up to the "wrong" vacuum source...