Excessive valve clearance cause low power?

On Sep 25, 6:34 pm, wrote:
wrote:

: How old are your sparkplugs? We've had a lot of trouble over the
: years with Champions, and used to buy the Auburns before Champion
: bought them up and shut them down. They were an excellent plug and
: almost always eroded to limits before the internal resistor failed.
: With Champs, we've had the internal resistor misfiring at 50 hours.
: One didn't work right out of the box. The Unison plugs are no better.
: A poorly-firing plug will cause a slight RPM drop. They need
: to be tested under pressure to see that they continue to fire up to at
: least 120 psi.

It's done the intermittent thing with new plugs, as well as freshly gapped and cleaned. Besides, if a plug wasn't
firing, the mag drop would show it (it doesn't... runs smoothly on each mag by itself).

Nice thought though. We've already done all the easy and normal stuff....

-Cory

The plugs will fire during the runup, one mag at a time, but
during flight when both mags are firing, there may be one or two that
don't. Engines that have both mags timed at the same point BTDC need
to be set as accurately as possible so that both plugs fire at the
same time or very close. If one fires well before the other, the
cylinder pressures may rise to a point that the other plug, being a
little weak, can't fire and now we get a bit of roughness and loss of
power.
There are a few engines that specify a significant difference
in their mag timing. I don't know how they handle spark blowout with
that setup. Some of them were pretty old models that used resistorless
plugs; perhaps they didn't suffer the same way that plugs with
resistors do.

Dan