Dear John:

Mechanically and technically, and while I'm not doubting your post and your experience with plugs,
this makes no sense.

If plugs are cleaned and gapped there is just no cause attributable to plugs that would lead to extra
fouling. If, however, the plugs had worn to the level where the electrodes are spaced too far apart I
can see where the uneven spark would cause uneven combustion which, in turn, would cause lead
fouling.

I'm racking my brain to think where time in service would make a difference - and the only conclusion
is mechanical failure, possibly a cracked ceramic area of some type of wear, if other than the
electrode gap?

If you ever learn more for the reason I'd sure like to learn about it.

My experience has been that plugs will last until the electrode tips are worn and unreliable - and
this can be 1000 hours or more if the cylinders are in good shape. If I had to make a guess, I'd say
that while plugs may be well maintained, they can wear due to heat or lean of peak operation etc.,
and that this may shorten plug life.

Pat




John Galban wrote:

"Dan Luke" c172rgATbellsouthDOTnet wrote in message ...

Is your O-360 bad about fouling plugs? Mine's terrible - much worse than the
O-320s on the Skyhawks I used to fly. I have to be an absolute fiend about
leaning to keep my plugs clear.

It's not nearly as bad as my O-300 was when running 100LL. Overall,
it's not really a huge problem. If I forget to lean for a long taxi,
I stand about a 50/50 chance that I'll foul a plug. It's usually
minor fouling and clears up after about 10 seconds of leaning durning
the run up.

Over the years, I've noticed that the age of the plugs has an effect
on fouling. When the plugs start getting around 400 hrs on them,
they tend to foul easier.

John Galban=====N4BQ (PA280-180)