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TR4/4A What gap on Champion L-87YC spark plugs?

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TuffTR250

Jedi Warrior
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I've got a TR4A engine in my TR3 which we just rebuilt. I'm running Champion L-87YC spark plugs. The book says to set the spark plug gap at .025 inch. That seems like a kinda small gap for an automobile engine. What gap is recommended for these Champion plugs in a newly rebuilt TR4A engine? Thanks!
Regards,
Bob
 
TR3driver

TR3driver

Great Pumpkin - R.I.P
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.025" was the pre-emissions standard for practically all car engines. The need for wider gaps came along with lean mixtures that were hard to light reliably, chokes that shut themselves off almost as soon as the engine starts and emission standards that said even a 1 in a million misfire rate was unacceptable. But the wider gap also takes more voltage to jump it reliably, so the entire ignition system (not just the points) needs to be upgraded to run them. Hence the huge distributor caps & rotors, fat wires, low impedance coils, electronic switching and so on that also came with all the emissions stuff.

So just relax and enjoy the vintage engineering. Believe it or not, it works quite well. :smile:
 
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