Distributor cap spark erosion relative life - brass vs aluminum

Question

Distributor cap spark erosion relative life - brass vs aluminum

Tmoose (Mechanical)

(OP)

2 Jan 19 14:50

Happy new year !

So I saved 5 bux and bought an A*t*z*n* aftermarket distributor cap for a 5 cylinder Volvo.

The one I took off was Bosch with brass contacts with plenty of erosion and fine dark metal spray extending a ways in either direction from the brass terminal. I'm thinking it might have even been original 1996. The brass rotor tip was a bit charred as well.

This aftermarket cap has aluminum terminals. (Reports are, some have brass terminals)

Realistically, what is the difference in life between brass and aluminum in this service ?

thanks,

Dan T

IRstuff (Aerospace) · Answer 1 · 2019-01-02 15:36:29

I would guess aluminum would have a slightly higher life due to better thermal conductivity, if it's a thermal phenomenon. However, I'm unclear whether erosion is a thermal phenomenon or a EDM phenomenon. If the latter, brass has a slight advantage: http://ijaiem.org/volume2issue8/IJAIEM-2013-08-27-...

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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itsmoked (Electrical) · Answer 2 · 2019-01-02 20:57:24

I've seen and used both interchangeably. I have to say I never found any difference worth noting.

Keith Cress
kcress - http://www.flaminsystems.com

TugboatEng (Marine/Ocean) · Answer 3 · 2019-01-03 05:02:55

RE: Distributor cap spark erosion relative life - brass vs aluminum

TugboatEng (Marine/Ocean) 3 Jan 19 05:02

Are you sure it's aluminum and not tin plated brass?

itsmoked (Electrical) · Answer 4 · 2019-01-03 05:40:58

Tug; I've scraped the corrosion off of lots that were definitely not brass.

Keith Cress
kcress - http://www.flaminsystems.com

Tmoose (Mechanical) · Answer 5 · 2019-01-03 17:28:28

https://images-na.ssl-images-amazon.com/images/I/8...

https://images-na.ssl-images-amazon.com/images/I/8...

=========.====

I don't expect to be peering into that distributor cap's nether regions for a few years, but here is a manufacturer who apparently is willing to state the contact material -

https://www.rockauto.com/en/moreinfo.php?pk=932467...

Regards,

Dan T

dgallup (Automotive) · Answer 6 · 2019-01-04 15:46:13

Among manufactures that make both, the brass terminals are always the "premium" product. Not really sure how much difference it makes. It's been a long time since I've owned anything with a distributor and I don't think I ever replaced a distributor cap. Points, that's another story.

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IRstuff (Aerospace) · Answer 7 · 2019-01-04 16:31:50

I've replaced a couple, one cracked and one with lots of carbon tracks; I think they all had aluminum terminals, but I'm not much of a "premium" product person.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

itsmoked (Electrical) · Answer 8 · 2019-01-04 21:44:39

Anybody remember the cap-fun a trip to the Quarter Wash would bring.

Keith Cress
kcress - http://www.flaminsystems.com

MikeHalloran (Mechanical) · Answer 9 · 2019-01-04 21:49:39

I remember coating the cap inside with silicone vacuum grease, which eliminated carbon tracking and made the vehicle more water resistant and much quicker to start on damp days.

No correlation found between terminal material and erosion/life.

Mike Halloran
Pembroke Pines, FL, USA

Tmoose (Mechanical) · Answer 10 · 2019-01-04 22:51:15

Hi Mike,

I am tempted to remove the new cap just to implement that greasy suggestion/recollection. Towards the end that car was demonstrating a tendency toward hydrophobia, but that I believe was aggravated by an oily dirty mess in the general vicinity, held captive by a well intentioned cover nearly integral with the cap.
https://dyw03owr7vs3n.cloudfront.net/public/assets...

thanks and best regards,

Dan T

MikeHalloran (Mechanical) · Answer 11 · 2019-01-05 21:12:37

A note of caution for lurkers:
DO NOT use just any old grease inside a distributor cap. Use only SILICONE grease.

The reason is simple.
Under stress, hydrocarbon grease decomposes to carbon, which is conductive, and will cause problems in a distributor.
Under stress, silicone grease decomposes to fine white sand, which does not bother the electrical components of a distributor.

Mike Halloran
Pembroke Pines, FL, USA

itsmoked (Electrical) · Answer 12 · 2019-01-06 08:38:27

T; That's a pretty small diameter cap so I could see it being a bit more problematic about moisture.

Keith Cress
kcress - http://www.flaminsystems.com

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