Distributor Cap

[PlayingWithTBI]

I think the part where the cap sits is different size on them, than on a Vortec distributor. Vortecs also have the flat part so the cap won't go on backwards.

And the TBI cap has the window for the ICM

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[HotWheelsBurban]

And the TBI cap has the window for the ICM

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Yup, so it looks like they are NOT interchangeable.....

 

[stutaeng]

When I changed the spider injectors on my K3500 (about 206k) I saw the distributer cap had a hairline crack (it looked original.) Since I had been having issues with my 4.3 (since 240k miles, and was like at 250k then) starting on wet/damp days, and that one already had the distributor replaced and countless caps. I hesitated on going to Oreilley's and decided to keep that cracked cap on the 5.7. It still works just fine, but don't know what to replace it with if it fails; luckily this isn't a daily driver, so miles don't pile up on it.

I'm not sure why these caps fail so often, but reading this now it seems it only affects the Vortec series? It seems like a basic piece to begin with. Just a plastic mold (insulator) with metal contact points (conductors); what can go wrong? I honestly wouldn't think brass or aluminum makes a difference, but no expert on this.

If they only seem to last 20-40k after getting replaced, why do the original make it past 100k w/o issues?

 

[evilunclegrimace]

United Motor Products at Rock Auto, Part Number DCR820X ,Blue cap with Brass contacts and a vent. includes the rotor, $27.79.

 

[454cid]

When I changed the spider injectors on my K3500 (about 206k) I saw the distributer cap had a hairline crack (it looked original.) Since I had been having issues with my 4.3 (since 240k miles, and was like at 250k then) starting on wet/damp days, and that one already had the distributor replaced and countless caps. I hesitated on going to Oreilley's and decided to keep that cracked cap on the 5.7. It still works just fine, but don't know what to replace it with if it fails; luckily this isn't a daily driver, so miles don't pile up on it.

I'm not sure why these caps fail so often, but reading this now it seems it only affects the Vortec series? It seems like a basic piece to begin with. Just a plastic mold (insulator) with metal contact points (conductors); what can go wrong? I honestly wouldn't think brass or aluminum makes a difference, but no expert on this.

If they only seem to last 20-40k after getting replaced, why do the original make it past 100k w/o issues?

They fail because the design of wires not crossing means that conductors inside the cap cross. Cheapy caps don't keep the conductors insulated well, for long.

 

[HotWheelsBurban]

When I changed the spider injectors on my K3500 (about 206k) I saw the distributer cap had a hairline crack (it looked original.) Since I had been having issues with my 4.3 (since 240k miles, and was like at 250k then) starting on wet/damp days, and that one already had the distributor replaced and countless caps. I hesitated on going to Oreilley's and decided to keep that cracked cap on the 5.7. It still works just fine, but don't know what to replace it with if it fails; luckily this isn't a daily driver, so miles don't pile up on it.

I'm not sure why these caps fail so often, but reading this now it seems it only affects the Vortec series? It seems like a basic piece to begin with. Just a plastic mold (insulator) with metal contact points (conductors); what can go wrong? I honestly wouldn't think brass or aluminum makes a difference, but no expert on this.

If they only seem to last 20-40k after getting replaced, why do the original make it past 100k w/o issues?

Original parts made in the US 25+ years ago, were probably made better than the aftermarket stuff now? Seems the design of these is prone to collecting humidity and that probably doesn't help longevity of any of the internal bits either. Also there's a misfire possible because of the way two of the passenger side nipples have to be placed to conform to the firing order? Seems I've read about this on here.
I want to replace the cap and rotor on the crew cab, since the truck most likely still has the one it left Flint , Michigan plant with 26 years ago. Start out with fresh stuff, then you have a baseline....

 

[HotWheelsBurban]

United Motor Products at Rock Auto, Part Number DCR820X ,Blue cap with Brass contacts and a vent. includes the rotor, $27.79.

Yup that's the one!

 

[L31MaxExpress]

When I changed the spider injectors on my K3500 (about 206k) I saw the distributer cap had a hairline crack (it looked original.) Since I had been having issues with my 4.3 (since 240k miles, and was like at 250k then) starting on wet/damp days, and that one already had the distributor replaced and countless caps. I hesitated on going to Oreilley's and decided to keep that cracked cap on the 5.7. It still works just fine, but don't know what to replace it with if it fails; luckily this isn't a daily driver, so miles don't pile up on it.

I'm not sure why these caps fail so often, but reading this now it seems it only affects the Vortec series? It seems like a basic piece to begin with. Just a plastic mold (insulator) with metal contact points (conductors); what can go wrong? I honestly wouldn't think brass or aluminum makes a difference, but no expert on this.

If they only seem to last 20-40k after getting replaced, why do the original make it past 100k w/o issues?

The cap on my 97 failed 2x during the factory warranty period. Once with a no start and the other time misfiring. The only caps I have ever been able to get more than 6 months to a year out of are MSD. The current MSD cap on my 383 was run on my 350 for about 3 years before the 24x swap I did on it. With the 383 I went back to a distributor. The engine compartment heat on a van cooks coils even on factory LS vans. Its cheaper to have 1 coil to replace and carry a spare.

 

[stutaeng]

Original parts made in the US 25+ years ago, were probably made better than the aftermarket stuff now? Seems the design of these is prone to collecting humidity and that probably doesn't help longevity of any of the internal bits either. Also there's a misfire possible because of the way two of the passenger side nipples have to be placed to conform to the firing order? Seems I've read about this on here.
I want to replace the cap and rotor on the crew cab, since the truck most likely still has the one it left Flint , Michigan plant with 26 years ago. Start out with fresh stuff, then you have a baseline....

I would leave it alone, and keep trukin' LOL. Buy the new one as a spare for an emergency!

Maybe that's what I'll buy then. The price seems right too.

One guy says use AC Delco, another guy says Delphi, another says United Motors, another says MSD, another says anything MSD is junk... NOS? Marine? There's absolutely no concensus. I don't know who to believe. Who knows?

We need a time machine to go back to the 1990s and steal of their OEM stock!

Or one of those more scientific Project Farm redneck testing videos like the ones on YouTube for testing aftermarket Chevy distributor caps!.

Sorry OP, not contributing any to your question...:-(

 

[Schurkey]

The brand-name on the box has little relationship to the factory (or even the country) that makes the part.

While this is true for heaps and piles of consumer goods, it was popular with automotive items--entire cars, and the replacement parts to support them--long before it was a big deal for other mainstream products.

Forty years ago, we called it "Reboxing". As an example, there were four companies making hydraulic lifters for Chevys, and a hundred companies that bought in bulk, put the bought-in parts in a custom-printed box, and passed them off as their own.


I would expect that when GM allows a change to a part--replacing brass terminals with aluminum, for example--they'd also issue a revised part number. I remember seeing thick paper books--3--4 inches thick, sometimes more--showing the part number history--the original number, superseded by a new number, sometimes multiple supersedings. The final number would either be the "current" part number, or the final version that was then discontinued. Seems to me the book also had the last-known price for the part.

As said, the typical problem with Vortec caps is that they've got the conductors molded-into the plastic, crossing over each other.

IF (big IF) I had repeat problems with Vortec caps, among the things I'd be looking at are plug-wire resistance, rotor-to-cap gap, and spark plug gap. Extreme resistance, or large gaps drive the voltage of the ignition system sky-high, making life intolerable for the ignition system insulation--including the plastic of the distributor cap.