Here's some info on reading and interpreting ignition scope patterns to get you started. https://www.motor.com/magazinepdfs/052001_04.pdf And of course there's some Youtube videos out there as well.
Thanks. That's good info there. There's some good stuff out there and in the manuals, but without the experience or anything to compare it to it's just guessing on my part, mostly. Should maybe try a different coil, or even re-install points and condenser, by way of comparison.
I'm a retired electronic technician and used a scope most days for 43 years. A scope gives a visual of what's going on. Thanks so much for all your information and pictures. Sent from my SM-S320VL using Tapatalk
Watch your scope patterns while the engine is running normally, especially the spikes for the spark voltage. Then pull a couple plugs and open the gap to .060" or so on one plug and close the gap to .020" or so on another plug and reinstall. Fire the engine back up and see if you can pick those two plugs out of the scope pattern.
My experience was with consumer electronics, but we did use scopes in automotive class 40 years ago . Sent from my SM-S320VL using Tapatalk
Yeah, the problem is I don't know what it's supposed to look like, as a baseline. For example all the firing lines are supposed to be about the same height in a good system. They vary depending on when the pic is taken, but average out better when looking at more than one pic. Probably not how it works when making a diagnosis, but then I don't know. Cyls. #5 and #4 firing line seem high. Can try adjusting idle mixture to even them out maybe. The use of resistor wires causes more of a bending in the spark line, it sort of looks like #6 has a sharp bend. The superimposed primary shows some distributor "cam wobble" but appears to be within 3° or spec, a new rotor tightened this up further by 1° for some reason.
It looks like you have the Heathkit manual which should explain those things. Trying to remember back 40 years ago auto class depending on where the inductive pickup was (Sun scope I believe) you could see all or lock out cylinders to analyze each one. If everything is ok they should all be equal. The scopes I have aren't specific for ignition but would work for it. There are lots of YouTube videos and this off is good... Testing your Ignition with an Oscilloscope. PDFPrinceton University › ignition_waveforms Sent from my SM-S320VL using Tapatalk
Yep, the assembly manual itself has some instruction, Heathkit also included "Minor tune-up with ignition analyzers" booklet, a Shell Oil reprint that is pretty detailed. It definitely idles smoother and crisp with fresh wires cap & rotor installed and everything squared away. Messed around a little with the idle mixture and got the firing lines a little more even. The coil wire is a carbon core resistance type, have another one that is presumed bad, and another that is new, but is low resistance spiral wire. Might be interesting to see how those stack up against each other.
I have a scope mounted above my work bench, I use it for working on vacuum tube style guitar amps. Wish I could help, but I wouldn't know the first thing about using it for car ignition. Squirrel has some experience doing this.
Yeah it pretty much paid for itself the first time I used it. Starting to get the hang of it a little bit, even the newbie is going to notice right away if something is screwed up ignition wise. Now I can understand why every shop had one, saves a lot of time, and it was also profitable, they could show the customer "you need a new distributor cap & rotor - here's why". A lot of people will look at the carburetor first when maybe they should be looking at the carburetor last. Already one of my favorite tools, along with a vacuum gauge.
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