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Date: Sun, 01 Jun 2008 08:47:33 -0400
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From: Howard Hamer <hamer@theunion.net>
Subject: [LML] Re: Electronic ignition spark plugs

A friend of mine recently upgraded his Tailwind from a stock O-290 to  
a souped up O-320. He had used a single electronic ignition with  
automotive plugs and mag with aviation plugs for years with the 290  
engine with no problems. The new engine would run fine at full power  
with the same set up for about 80 seconds then sputter and backfire  
until he pulled the throttle to idle. We spent weeks looking for the  
problem with the fuel system but after each mod we could still only  
get 80 seconds of full power. Finally I noticed the tips on the  
automotive plugs had color pattern that indicated they had been very  
hot. We change to aviation plugs and have had no problems since with  
the ignition system. We suspect we were getting pre-ignition. Only 80  
seconds of power made for an exciting first flight after the engine  
change.

Rusty