early spark plugs

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early spark plugs

Postby jerry1927 » Mon Jan 05, 2009 9:37 am

I recently obtained one of Larry Jenno's Ohlsson .12 engines, a "copy" of the one-of-a-kind original from 1935. Its plug is 1/4-32 and may not be like the original. Dan Calkin came up with that size to fit his "Corncob" of 1936. Can anyone tell me the actual size of the Ohlsson .12 spark plug and who made it? I suspect the smallest production plugs during that era were 3/8-24, pretty large for a .12. Maybe Irwin made his own plug for that engine.
Thanks.
Jerry
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O&Rplugs

Postby max hansen » Tue Jan 06, 2009 3:15 pm

Jerry,What I have found is that all Ohlsson , O&R engines used the small 1/4 X 32 plug up to some time in 1940 when they went to the 3/8" one in the .60's. I think Ohlsson only made a couple of .12's . Max H. :)
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small spark plugs

Postby jerry1927 » Tue Jan 06, 2009 3:59 pm

Max,
Thanks for your response. I was aware of your info but recall that the .56s and .60s used the 3/8 in. plugs, at least until they introduced the RVs. My confusion is due to the timing of introduction of the experimental .12, 1935. It appears to have been made BEFORE Dan Calkin came out with his 1/4-32 spark plug for his "Corncob" in 1936.
Champion fired the insulators for those Elf plugs (they showed Champion's name even though the design was Dan's,) and Dan assembled them into his machined bodies. They differed from Champion's later equivelant plug in that the ground terminal was a wire that was secured to the threaded body at both its ends, reaching across the body & just missing the center electrode. Gap was adjustable by bending of the ground. I have one of those spark plugs.
Jerry
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O & R PLUGS

Postby max hansen » Wed Jan 07, 2009 12:45 pm

The early engines I have never had too much to do with (always cost too much). The Customs & Specials I have had almost every model through the shop . What I have found is that the early Customs (1940) came with a 1/4" plug . The later & last Custom had a 3/8" plug & when the Special came out it was with a 3/8" plug & stayed with that size until the last sideport(aluminum head) in 1949 & that had a 1/4" one .
Had a Minature to rebuild one time but it was so messed up I sent it back to the owner . It had a homemade front cover w/ a Super Cyclone timer & a connecting rod that looked like it was made with a hammer. Not worth it .
Had one of those early plugs w/the electrodes like you are telling about but I thought it was just a bad glow plug & put it in a old engine I sold to keep the dirt out of the cylinder ,not too smart I guess . CYL, MAX H. :)
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Postby chiefss » Wed Jan 07, 2009 1:03 pm

I have several V-2 plugs that are 1/4x32 if you need one. They are used but all work well.

bruce
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V-2 spark plugs

Postby jerry1927 » Fri Jan 09, 2009 9:16 am

Hi, Bruce,
Yes, I am interested in your V-2 spark plugs. How much do you want for all your good ones?
You can make a personal reply via e-mail, if you wish.
<gerald_w10@hotmail.com>
Thanks.
Jerry
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