Vortec 350 distributor cap life.

[rfoll]

My neighbor has a 1999 or 2000 1 ton Chevy van with a Vortec 350. Distributor caps only last about a year and then he starts getting misfire. Anyone have any Ideas what is going on? The caps he buys from NAPA have a 3 year warranty, but it is still a pain.

[pamotorman]

try one with brass contacts instead of aluminum. make sure the wires are all the way into the cap as i have seen where the wire was not all the way seated and it burned thru the side of the cap

[af2]

I can always tell after the first rain when the cylinders start swapping when cold then run fine after 5 miles. Last year I went through 2 caps on mine. The factory cap lasted 100,000 miles now I get 6-7,000 with after market crap. Turn the crab over and you can see trails all over.

[ja411]

Remember spark is looking for the easest path to ground. Check wires, plugs and rotor. See which cylinders are crossing in cap and check those cylinders.
Joe

[RevTheory]

I blew through the rotor a couple of times when I was trying to run more than .050 plug gap.

[user-17438]

Make sure that the vent isn't clogged..

[rfoll]

Thanks for the replies. I will ask about plug gap, and get a look at the old cap.

[Schurkey]

I'd be looking at the PCV system. Pressure in the crankcase could push fumes/moisture up the distributor shaft, where it contaminates the inside of the distributor cap.

Similarly, failed intake gaskets allow coolant into the oil. When the engine warms-up, the water evaporates. Humidity could climb the distributor shaft and foul the inside of the cap.

Lastly, all of the above is more common when the distributor shaft bushings wear out.

[Ed Wright]

The Vortec truck distributor caps sweat & carbon track worse than most. We learned to stocked up on them at my shop in Oct each year. NAPA would always run out, had my own put back. Use brass, not alum posts.

They are not originally vented. I drilled a 1/16" hole in the top of the square recess that would face the firewall. There are two, they look like where something would snap in place there. The hole comes out between 2 plug wire posts inside. Never had a customer have another cap issue after that. I used to cut pieces from old caps to epoxy in place to shield water from the vent holes I drilled. Facing the firewall, not visible.
Got to replace a lot of those caps every fall. Temp changes in the damp air made them sweat badly. I had a very busy shop that only did AC work, tuning, drivability & diagnostics, on only Ford & GM vehicles, for over 40 years. Got to see a lot of stuff like this.
I found NAPA (Echlin) caps to last better than any others I tried.

[BOOT]

Make sure the center of the rotor is touching the cap bushing, might have to bend it up.

[Geoff2]

There are TWO gaps the spark have to jump. Most people only worry about the plug end, the gap between the electrodes. Nobody thinks about the gap between the rotor tip & the segments. Make sure it is not too wide, or...arcing & short cap life can result.

[pamotorman]

There are TWO gaps the spark have to jump. Most people only worry about the plug end, the gap between the electrodes. Nobody thinks about the gap between the rotor tip & the segments. Make sure it is not too wide, or...arcing & short cap life can result.

GM started to put shorter rotor tips as part of the emission reduction and these rotor tip had a "E" stamped on them.

[turbo2256b]

I have had a lot of trouble with MSD dizzys and moisture freezing up the advance mechanisms and caps. Their response was to move to a dryer climate. Always carry a few spare caps with me. Been giving a lot of thought about going with coil pack conversions.

[pamotorman]

I have had a lot of trouble with MSD dizzys and moisture freezing up the advance mechanisms and caps. Their response was to move to a dryer climate. Always carry a few spare caps with me. Been giving a lot of thought about going with coil pack conversions.

use a marine cap as they have a screened vent. to let out the moisture

[rfoll]

These are funny looking caps with the firing order arrageged by routing in the cap. Is the marine cap the same?www.summitracing.com/parts/dfp-dc20010? ... FwQAvD_BwE