do plugs wear out?

[Jerry In Maine]

Take a used spark plug in reasonably good condition. Wire brush it to remove crud, if necessary use a fine file to smooth and brighten electrodes, rinse in solvent to remove contaminants , and re-gap.

Will it now perfrom as well as a virgin plug fresh out of the box?

Is there anything within the plug that gets depleted thus lowering its effectiveness?

[The Tinker]

Sand blasting does a better job of cleaning them. Cleans of all the carbon tracks.

[david1230]

Unless you can get your hands on a couple of 8COM 2-part plugs. For my WS they're the best performing and can be taken apart for a thorough cleaning.
Too bad they're rare and those sold on eBay are quite expensive I've been told.

[Jerry In Maine]

i'm thinking that a properly cleaned and gapped plug is good as a new one - at least i don't think you could tell the performance diff w/o instrumentation of some sort. i do have a glass bead blasting cabinet so i can clean them as Tinker suggests.


this is no big deal as plugs are cheap. i was just curious.

[1650bullet]

As Tinker said, Sand blasting and a regap brings them back to new. I have a few old ones lying around. Im going to build them up and take them to my friends house and do them all in his bead blast cabinet so i have a heap of spares.

[Keith.P]

Sounds like a good idea, I will have to get my never unused spark plug cleaner out.







The only problem is, I don't think it will do 18mm plugs.

[Collector Inspector]

If old plugs spark under compression after cleaning up that is all you need

If you have a "Classic Plug" sparking well...............That is totally Cool!

B

[Gannet]

I have always assumed that the ceramic insulation breaks down. I thought that the surface of the insulation developed small cracks either running along the surface or through the insulator itself. Once these cracks contained a conductive material then this would aggravate the situation and poor plug performance would result. I assumed that thermal and pressure cycling caused this mico cracking. Additionally I would expect a clearance to develop between the central electrode and the ceramic - again due to thermal and pressure cycling - as the relative expansion rates of the electrode and the ceramic must be very different.
However, perhaps in a high performance high reving engine like a Seagull, the life is very long!
Jeremy

[spiderg]

Does all that mean "once a plug's done it's done" Jeremy?

[david1230]

I philosophically compare my 41 year old 8COM plug on my WS to those on a 1937 Chevrolet I used to own in my earlier days. It had six original sparkplugs (forgot what type), and they still had plenty of spark then.
I'm still in contact with the guy I sold the car to in 1975 and yep...same plugs! Those are now 75 years old and are still firing the old Chev's straight six. They have never even been cleaned once!
So personally I'm not worried about my 8COM plug deteriorating or cracking up. I just keep it clean.
I'm not an engineer, but I think the longevity factor is due to the fact that the Gull isn't a high-performance or high revving engine (unless boosted for racing of course).

[Gannet]

I would think that once a CLEAN plug fails then it is going to continue to fail if it is under the same running conditions.
Likewise, I would think that if a plug in a specific engine is working well, then unsurprisingly it will continue to work well for a time.
The timescale to failure might well be very long indeed, as has been pointed out, especially in low performance engines running a low number of hours each year.
I suspect that a lot of us have experience of a specific make and grade of plug that has not lasted in a specific engine. We have probably also experienced plugs that last and last. The variables are enormous.
Jeremy

[Jerry In Maine]

As Tinker said, Sand blasting and a regap brings them back to new. I have a few old ones lying around. Im going to build them up and take them to my friends house and do them all in his bead blast cabinet so i have a heap of spares.

that gives me a chance to show-off the home-brew bead blast cabinet i just built. side panel comes off to allow the mounting of an extension cabinet - nice when you need to blast large items. rig near the little vacuum is a cyclone to spin out and recover usuable blast media that would otherwise get thrown away.

[skyetoyman]

I'm NOT jealous. I had a Ronco spark plug cleaner. Sadly got rid of it when I went to diesel.

[Daryl]

Yes spark plugs do wear out. The center electrode wears & when its rounded it takes a higher voltage to fire the mixture. In cars it usualy shows as intermittent missing on acelleration. Due to the relatively cheep price of new plugs its hardly worthy while filing the center electrode & re gaping. It would take a very long amount of hours use in a Seagull to wear the center electrode. More likely to suffer from fouling deposits than wearing out.

[Keith.P]

Yes but seagulls use 18mm plugs and not common or garden 14mm, I can get very cheep cheep new plugs for my OMC motors and they don't look any different than the originals.
The two piece plug used in the older Seagulls look the part with the right cap and a new original plug is not cheap and something to throw away after a little use, also filing a plug is not exactly rocket science.
The same thing happens with points and its not as though you can pop down to Halfords for either.
I used to use platinum tipped needle point racing plugs back in 70's and they were £15 each, that was bad enough.