Rotors don't wear out and need replacing nearly as often as parts
manufacturers would have you believe. While I've had rotors fail
mechanically, that is actually quite rare.
You get a couple of things going on under the distributor cap that cause the
rotor, and cap, to wear out.
The rotor spins against the carbon button in the center of the cap. This
produces carbon dust that coats everything. That promotes arcing to ground
and not the plugs. Once this starts, usually called carbon tracking, it's
remarkably difficult to stop it. The carbon tracks get embedded into the
plastic and wiping doesn't remove them.
As the spark jumps across the small gap between the rotor and the cap lug it
produces an arc and blasts a little bit of the metal off. Make it a soft
metal like many cheap caps use, and you can really wear things away after a
few million arcings. Now you've got a great big gap instead of a small gap.
Which promotes misfiring. The metal blasted off by the arc is usually
vaporized and gets to redeposit itself inside the cap just like the above
carbon does. Again, promoting arcing to ground and such.
While it would sound like you could clean up the rotor and just replace the
cap, that will generally wear out the carbon contact button in the center of
the cap in short order. The rotor gets worn from the previous carbon
button, and doesn't match up well with the new one, and grinds it down.
Sorta like putting new brake shoes on nasty brake drums, the shoes wear out
quickly as a result.
Wipe down the inside of the rotor and cap to prevent carbon arcing from
every occurring. Dress the contact points on the rotor and the cap. Do
that and you can add many years to the life of the components.
----- Original Message -----
From: "Bob Danielson" <75TR6@tr6.danielsonfamily.org>
Subject: [TR] Do Rotors Really Fail?
> Do rotors really fail
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