What makes these trucks destroy distributor caps/rotors?

[redfishsc]

I have one truck in particular (1999 C1500 Sub) that will ruin a distributor in about 6 months. Also, it seems to really have a craving to do it at the most ridiculous times.

My first cap was a brass Autozone Durasomething. All the others have been AC Delcos, with aluminum. I'm taking a wild guess here that Delco sucks in this case since the brass held up longer.

I've read that we should probably be drilling some tiny holes in the cover to provide ventilation. I DEFINITELY live a stupid-humid, hot environment (coastal SC).



If you want to read my sob-story, here it is. Truck just loves to act up on ironic/bad days.

1) My second son was born. Started misfiring THAT DAY as I drove back to the house to check on my in-laws and older kids. Misfire, #3 or 5, can't remember. New distributor cap solved it.

2) 9 months later, pulling out of driveway for a 300 mile trip with the family....started misfiring. Cyl 5. New distributor cap solved it.

3) 4 months later, driving to the parts store to buy some hand tools to begin my front end rebuild.....started misfiring, Cyl 5. Taking a wild ass guess about what it is.



My OTHER 99 Suburban (K1500), same engine, is about a year on the Delco (aluminum) and it runs like a champ.

 

[454cid]

Usually it's recommended to get AC Delco caps. There are several problems. First the caps cross the conductors to some of the cylinders, so the conductors inside come very close to each other. I guess if the cap isn't made well it's starts shorting internally. Plus, the bodies of the distributors are plastic, and the tabs where the screws go can crack or break off. Eventually, the gears can wear, too, but that's not specific to our distributors. If you're having that hard a time with a particular truck, I'd look at replacing the entire distributor, but I'd still recommended an AC Delco cap be installed. Please note, I'm repeating what I've read on forums... mine has been trouble free for over 280K miles. The cap has been replaced once with an AC Delco.

You didn't mention the rotor, but I assume you're replacing that too.

My dad's old 96 had a no start condition several times and a cap replacement fixed it, but not as often as what you mention.

 

[letitsnow]

Always cylinder #5...

 

[Supercharged111]

Are your factory breather screens plugged?

 

[kennythewelder]

Factory breather holes got clogged up very easy. When they do, you dizzy will eat up caps and rotors.

 

[L31MaxExpress]

I took a lesson from the optisparks and used vacuum to vent my cap when I still ran a distributor. Mine was eating a cap and rotor about every 3-6 months. The factory vent holes were free and clear as well. I used a small 1/8" vacuum line and hooked it to manifold vacuum. Drilled the base of the distributor and tapped in a couple of small brass elbows with 1/8 hose barbs that I reinforced with JB Weld. I drilled a small hole above the throttle plate in the throttle body and JB welded a small piece of 1/8" aluminum tube. I ran a 2nd vacuum hose to that as a filtered fresh air vent. As long as I had an actual distributer I never ate a cap and rotor again. 4 years and 30K later it was still going strong when I finally went EFI Connection 24x. I think my issue was it not being driven daily or even weekly and moisture staying in the cap from the fact it was driven mostly short trips.

 

[Ken K]

Suerpcharge111 & L31maxExpress are both right. The flat cap design to get cross-fire away from each wire, but in the base of the distributor is a vent. This is why the bottom of the rotor is cast with a fan design on it. It moves the atmosphere around inside the cap. When spark occurs, ozone is created, this is what eats away at connections. Adding a positive vent system is the best idea I have heard in ages. No one looks at the screen / vent in the base of the distributor because it can't be seen without it upside down. The OptiSpark distributors had a first design then second. The vent hose to the air cleaner tube was added at this point. This helps remove the ozone (O3) when running. Upgrading to new ACDelco wires with the inductive type will help. These are 1,000 ohms wires with an actual wire coil wrapped around an arid core. Dielectric grease on the wires on both ends will help with seal, but not inside the cap. That vent hole is a common inspection point and hit it with compressed air. Make it larger would help, but adding a second one with positive evacuation is brilliant.

 

[c1500deathtrap]

I always add a vent inline with the rotor, drilled through the cap from the side. And i spray down the inside of the cap with mil-prf-81309 ty3. >> https://store.lhbindustries.com/mai...aerosol-0964------000?returnurl=/search?q=cpc
its used a lot in aviation to keep electrical contacts from corroding. I never have any problems

 

[Ken K]

The formation of ozone, moisture and crankcase gases all find their way inside the cap. The combination of these compounds with humidity create nitric acid. This is what's eating up cap parts. Just adding ACDelco spark plug wire information. New wire wound plug wires measure 1K ohms total, while the carbon filament type wire measure 12k ohms per foot. These new one deliver 25% more voltage while keep RFA down.


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[homeslice]

I recently installed a new L31R with summit billet distributor. I followed the Aloicious procedure for dizzy install, and it worked perfect. Started right up, and did not register any codes. Less than 6 months after install, it ate a dist cap. I forget which cylinder it was, but one of the contacts was destroyed on underside of the cap. I had also noticed it would start strangely like it was slightly out of time.

I'm now doing the 0411 swap, and have learned about Cam Offset Retard. I'm thinking this is what ate my cap, as I was slightly off on the setting, 2 degrees. I must have been right on the edge of not getting a code for it. I adjusted the dizzy, and no more strange sounding starts.