Champion J6J or J6C

[foot_doctor]

My racing partner, Chuck Erdman and I were running a 25SS in my test tank one Saturday afternoon many years ago. Our goal was to test a varity of spark plugs for performance differences. We tested a bunch of plugs, and in a final test, we installed my ignition test plugs. They were Champion L4J with the ground electrode removed in the lathe. Holy Cow, the engine ran faster than any other plug allowed. We duplicated out tests several times, with several different test wheels, and always a consistant water level in the tank. Thereafter, every 25SS powerhead I built for anyone was equipped with the modified L4Js. Ironically, many of the racers I built the engines for thought that I mistakenly left in a set of test plug, and never tried the engines As I provided. Their loss I guess, as we had discovered a proveable performance improvement. The Mercury ignition system was more than up for the challenge of the extreme spark gap, and we never had an ignition issue during all of the years that we ran the 25SS engines. On a side note, the 25XS engines did not respond to the large gap plugs in any style or brand. R.T.

[Pete]

Excuse the tread hijack

R.T. Very interesting, as I recall that info never made it to us racers in Region 5 in the 70’s, would have tried it. Was the L61Y in your testing? Per my "Champ Hi Performance Heat Range Chart and Tuning Guide" the L4J is the coldest in that series and a little hotter than the colder L61Y. So basically without the side electrode the L4J was a side fired plug. Essentially like what I tried with the L61Y with no ground electrode except the Y has a projecting center electrode compared to the shorter J center electrode.

The test tank is one thing how did the modded L4J’s run when testing on a race boat and on the race course? Did you ever get rpm and speed readings compared to other plugs?

I will get a set of L4J (now L82C from search not sure if identical to the original L4J?) and try them modded as you did.

On the 25ss engines you built what crank end play did you use? I was surprised to see on the tag that came with my engine in 1973 from Dick O’Dea that stated end play at 0.003" to 0.010", the lower # seemed way too small. I set around 0.008" and use the long stops with 0.012" SS reeds.

On the 25xs maybe the loop charge design was way more efficient than the deflector design of the 25ss that large gap made no improvement with the fuel combustion flame front travel?

I still run my 25ss and any engine build and ignition tips you recall would be appreciated. Thanks

Pete

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