I've read it a million times, check cap for evidence of carbon tracking. Never paid too much attention to it though. Cleaned up an old cap had laying around and started to look close. Under strong light especially all these scritch marks and weird stuff shows up. Is that what that is? Also the bakelite where the terminal exits has eroded or burned away. The terminals get a crusty layer or corrosion after a while. What causes this and can it be prevented.
I am not seeing any carbon tracking in that cap. Carbon tracking will be a black line that will trace to a ground or another terminal.
Well that's what I thought. What causes all those scritches and scratches though? Sand or dirt maybe?
That white line is high voltage Corona Tracking (not the beer) Gap is too wide, The cap needs a breather out the top like MSD's, Mallory's, etc. There is a way to help eliminate that but it's one of my "speed " secrets and not necessary if you have the right gap on a street engine. That arcing also causing the the metal to look then way it does, it's jumping to far.
I was told the corrosion on the contacts was caused by the rapid rotation of the rotor churning up the air in the distributor combined with high voltage generating ozone gas inside the cap. It is the ozone that builds up the deposits on the contacts. Venting the cap will help in preventing that, and even drilling a hole in the top or side of the cap will do it.
Well I wondered about that. I replaced the cap and found a rotor that runs a lot closer gap, we'll see how it looks after a few thou. Thanks Real interesting stuff, that high voltage. This was the gap on the old rotor
It's not corrosion. Corrosion eliminates material. This is an addition...of material. Not sure exactly what is called, but it's a "left over" material from the corona or plasma of the cap and rotor sparking. Remember, there's a lot of voltage and amperage jumping that gap. Take one of those small "give-away" screw drivers...and carefully s****e it off the terminal. It will leave the original mostly shiny (aluminum/br***) surface. You will need to take a light file to smooth the rotor tip. Mike
Yep that's exactly what I did, what you see now in the pics is after cleaning all that **** off. It looks like at one point it got so bad that the spark was jumping down (or up) to clean metal at the top of the terminal, and eroded away the bakelite.
Fordors, corona and ozone are "partners" in high voltage ( not friendly) Saltflats, now that would be a sight to see; it's not what I do but what I do works and has for over 30 yrs. Being a high voltage power plant electrician for over 40 yrs does have its advantages. One is knowledge the other is a very good retirement.
So, what is the benefit of wide gaps between rotor and terminal inside distributor? OEM went to wide plug gaps, and wide rotor gaps, to increase coil firing voltage, to meet 70s era lean burn emission requirements. At least that's my understanding. I can understand the wider plug gaps. Why though, two wide gaps in the secondary circuit, wouldn't just one (at the spark plug itself) be enough? The wide gap inside the distributor can cause problems, so why did the OEM decide the tradeoff was doubleplus good & worth it? See where I'm goin' with that?
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