Oscilloscopes...

[TrimixToo]

Mitchel manuals used to have these articles in their magazines designed to teach noobs and oldsters about new technology. I was always fascinated by them, reading more than my share. I do remember reading that condensers (capacitors) were sized to provide the proper spark duration. Too close or far, and it will cause pitting. Pitting and being non-parallel makes gapping points nigh on impossible. Since most were nickel plated, sanding or filing them to be smooth, ruined the finish. Using a dwell meter allowed you to set points precisely, regardless of any imperfections.

Yes, a dwell meter can let you set pitted points properly. But as the plating is already shot (along with the condenser if it was the right size), it's a temporary fix at best.

I thought the condensers were sized to absorb the remaining energy contained in the collapsing field in the ignition coil after the plug fired and the secondary coil voltage dropped to the point where the plug would no longer spark. This prevents a spark from forming across the points as they close. Too large, and one side would pit. Too small, and the other side would pit. At one point in my life (pun intended) I knew from the direction of pitting whether a condenser was too large or too small because changing coil size could affect the right condenser size.

But...it's been a long time, points and condensers are in the trash bin of history as far as I'm concerned, and I'm not going to go look it all up (grin).

 

[broncobowsher]

I remember in high school auto shop there was a discussion about the pitting and tuning with different condensors.

My last set of points, well they are still there. But not the condensor. I converted the points from a load based system (that pits the points) to just a trigger system. Using a Ford remote mount TFI module and E-core coil I get the massive spark from a great late model ignition system, but I keep the unicorn marine mallory distributor intact. I learned about the TFI module with points from people doing it on old Honda motorcycles that had a crap ignition system and it was there upgrade. It triggers on the falling edge (like points) so the phasing is correct. Some other conversion fire on rising (when points close) and that is hard to fix. Another great thing is the point dwell really doesn't matter. Anywhere close is good enough. The module controls the coil dwell itself. And you get to delete the ballast resistor.

 

[Tracy]

I remember in high school auto shop there was a discussion about the pitting and tuning with different condensors.

My last set of points, well they are still there. But not the condensor. I converted the points from a load based system (that pits the points) to just a trigger system. Using a Ford remote mount TFI module and E-core coil I get the massive spark from a great late model ignition system, but I keep the unicorn marine mallory distributor intact. I learned about the TFI module with points from people doing it on old Honda motorcycles that had a crap ignition system and it was there upgrade. It triggers on the falling edge (like points) so the phasing is correct. Some other conversion fire on rising (when points close) and that is hard to fix. Another great thing is the point dwell really doesn't matter. Anywhere close is good enough. The module controls the coil dwell itself. And you get to delete the ballast resistor.

I converted my big boat to GM HEI marine distributors last year. Outside of my forklift and beetle, those were the only thing I had left with points. While I appreciate the simplicity of points, I don't miss the tweaking and adjusting.

 

[The Chairman]

I thought the condensers were sized to absorb the remaining energy

It's to lengthen the duration of the spark to make it useful. Without the condenser, the field collapses too quickly, and the car will misfire. You can easily see that on a scope and avoid premature point failure.

I have a boat in my yard with an Iron Duke engine that still has points and a carb. It's too noisy for me, so I've pretty much abandoned it as a project.

 

[The Chairman]

And you get to delete the ballast resistor.

That's a function of the coil used. I went through the bigger/badder spark fad in the early 70s. But then, it occurred to me that a spark is a spark. You only need to really worry about it if compression is way high, or the carb is too lean. Today's coils have a hyuge wallop. Sheeesh! Get too lean, and you have a heat problem which can be ameliorated by retarding the timing and installing an EGR valve. One of the last things I did to my 67 Cortina, was to switch to an optical ignition system. Before that, I installed a dual overhead cam head (from a Lotus), and swapped out the generator for an alternator. I was close to adding AC, but then I was given an AMC wagon, that was power EVERYTHING! It had a V-8, an automatic transmission, and faux wood siding, which I laid in real birch and mahogany. It carried my canoe, which was important to me back then.

Talk about going off-topic on your own thread.

 

[Gone for diving]

My voltmeter in a test light is the handiest thing... good to 36v reads down to 3.5V.... so not good for voltage drops. That's the only thing I don't like about it.. just part of the design....

My little scope I don't use that much,
Because I don't get into CAN problems to often. But great for testing inverters.

I still carry a regular test light for adding small loads, and as stated, for points and stuff like that.

 

[TrimixToo]

It's to lengthen the duration of the spark to make it useful. Without the condenser, the field collapses too quickly, and the car will misfire. You can easily see that on a scope and avoid premature point failure.

I have a boat in my yard with an Iron Duke engine that still has points and a carb. It's too noisy for me, so I've pretty much abandoned it as a project.

Oh, poo. You made me actually look it up. These folk and others disagree:

How Ignition Systems Work

How Capacitors Protect Ignition Circuits

A capacitor is a two-terminal electrical device that stores and releases energy as an electric charge.

www.tomorrowstechnician.com

However, I had the sequence wrong. It's there to absorb the initial energy from the field collapsing, not the residual. If I were less brain dead when I wrote that I'd have realized it had to be wrong!

 

[TrimixToo]

That's a function of the coil used. I went through the bigger/badder spark fad in the early 70s. But then, it occurred to me that a spark is a spark. You only need to really worry about it if compression is way high, or the carb is too lean. Today's coils have a hyuge wallop. Sheeesh! Get too lean, and you have a heat problem which can be ameliorated by retarding the timing and installing an EGR valve. One of the last things I did to my 67 Cortina, was to switch to an optical ignition system. Before that, I installed a dual overhead cam head (from a Lotus), and swapped out the generator for an alternator. I was close to adding AC, but then I was given an AMC wagon, that was power EVERYTHING! It had a V-8, an automatic transmission, and faux wood siding, which I laid in real birch and mahogany. It carried my canoe, which was important to me back then.

Talk about going off-topic on your own thread.

We can lead you further afield without much difficulty (grin). Just ask!

 

[broncobowsher]

Or don't ask, and we will just go there anyway.
And a good write up on using the TFI module with points https://www.49ccscoot.com/manuals/FORD TFI electronic ignition.pdf

 

[The Chairman]

These folk and others disagree:

That's a DIS system and not a points system.
The cap here is on the supply side, on points, it's on the ground side of the coil.

“Since it’s on the power feed side,​

When the points open the coil (transformer) primary field collapses, inducing amplified volts on the secondary side. The greater the capacitance, the longer the duration of the spark. V-8s need lower capacitance than a 4, just as the dwell (point gap) is also smaller. If the gap is not sufficient, then there is a possibility that the cap will not fully discharge. Too brief of a spark and you might not light the fire. You can always run a v-8 cap in a 6 or 4, but not necessarily the other way around. While carb issues can affect the strength of the spark, they don't affect spark duration. Best practices are set the dwell, then the time, check for proper spark advance and then adjust carb idle. I have no idea how many hundreds of points systems I had to diagnose and repair. I've heard all sorts of whacky ideas from them being a "false ground", to... well it's been a long, long time. On most cars, dwell was set with the distributor cap and button off. GM had little windows in the distributor caps you could slide up and insert an allan wrench to adjust it while idling. Damn, I think it was GM (AC-Delco). I was almost exclusively imports until the mid 80s. By then, points were starting to become rare. More and more, my fellow auto-technicians had never installed points, changed out a generator, or truly relined a set of brake shoes. Slapping on a set of rebuilt shoes doesn't count. Most had no idea what the first emission control device was, and had never rebuilt a fuel or water pump. They had become effing parts changers.

Little known fact: except for the 009 (Porsche or racing) distributors, VW retarded the 3rd cylinder to keep the heat down. It was important to match that retarded electrode accurately, or possibly burn the #3 piston exhaust valve. If you installed a 009 distributor, be sure to retard initial timing a degree or two.