Spark plugs - Sarb11
Just about to fit some new spark plugs. Question is why do they come with a silver bit that you screw on the end (over the end that connects to the lead) and do you need to put this silver bit on?

If you do need to put it on then why not make them that way in the first place? Hope this makes sense.

thanks
Spark plugs - jc2
Some plugs come with fixed ends;the "silver bit" does not come off.Earlier high-tension leads either clipped onto the threads or had a hole in the end of the lead and was kept on by screwing a nut or the "silver bit " on.Modern ones clip straight onto this bit.
Spark plugs - MW
Thats correct, just screew then on. Actually, I havn't seen them seperate for years. Most manufacturers would not want customers saying 'a bit was missing in the box.'
Screw the plugs in by hand a first, 'feeling' the thread to make sure its not cross threaded. A smear of copper paste on the thread helps, and stops them binding into the head.
Spark plugs - robcars
The same spark plug will fit more than 1 vehicle. Some (especially volkswagen) leads clip on to the plug without the nipple attached whilst others need the nipple (no comment!).

Spark plugs - Pete M
NGK, in particular do some very nice plug caps with a spring-loaded socket that make very good contact with the threaded portion. These are common on motorcycles. The nipple is usually made of aluminium, which is a good conductor, but prone to corrosion.
Spark plugs - Cliff Pope
Why is it that even though screwing the silver bit on tightly, next time you pull the lead off it is always lose? How quickly after fitting a new plug does the silver bit come lose, so does it matter?
Spark plugs - L'escargot
How quickly after fitting a new plug does the silver
bit come lose, so does it matter?


It doesn't generally matter because the voltage generated is sufficiently high for the current to jump a small air gap. In fact at the business end of the plug the current jumps a substantial air gap to produce the spark.
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L\'escargot.
Spark plugs - L'escargot
Why is it that even though screwing the silver bit on
tightly, next time you pull the lead off it is always
lose?


Thermal expansion and contraction?
--
L\'escargot.
Spark plugs - L'escargot
The same spark plug will fit more than 1 vehicle.
Some (especially volkswagen) leads clip on to the plug without the
nipple attached whilst others need the nipple (no comment!).


And the plugs originally fitted by the car manufacturer have (or used to have) the nipple integral with the plug because the large quantity they buy make this the most economic way. When I worked for a car manufacturer being caught with a set of plugs like this in your car was sometimes sufficient proof that you had stolen them!
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L\'escargot.
Spark plugs - sierraman
When training for mobile tuning I was told to nip the screw on piece tight with pliers to ensure it did not work loose.
Spark plugs - Aprilia
Yes, that's what I always do.
Spark plugs - LeePower
I use a drop of super glue to keep the sliver bit screwed up tight on the end of the plugs.

I fitted a set to a VW OHC engine the other week & had to unscrew the silver bits because it had the different type HT leads fitted.
 

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