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Magnetos, Ignition Coils and Spark Plugs Discussion about magnetos, buzz coils, spark plugs, ignitors and low tension coils.

Magnetos, Ignition Coils and Spark Plugs

AC LM 46-B spark plugs


Anybody seen any for sale lately? I have not seen any on EBay for quite a while now. I am looking...

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  #1  
Old 01-22-2013, 04:58 PM
Andrew Mackey Andrew Mackey is offline
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Question AC LM 46-B spark plugs

Anybody seen any for sale lately? I have not seen any on EBay for quite a while now. I am looking for some in working condition, for my American La-France V-12 fire truck engine.
Andrew
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Old 01-24-2013, 07:06 PM
Dempster Dempster is offline
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Default Re: AC LM 46-B spark plugs

Will look later but don't think I have those. What size thread or length? Is there others that will sub? Might check Stitt, BG, or Beru / Borg Warner if they have something or maybe more will show up later online for you.

http://www.stitt-sparkplug.com/

http://bgservice.com/4.html

http://www.beru.com/products/non-aut...or-gas-engines
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Old 01-25-2013, 09:36 AM
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Paul Spence Paul Spence is offline
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Default Re: AC LM 46-B spark plugs

Andrew: I haven't seen any AC LM 46-B's for a while . I keep looking for them at the "FLEA" markets in the used spark plug buckets I sometimes find, to add to the collection , but nothing....... .
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Old 01-25-2013, 01:53 PM
Doug Sather Doug Sather is offline
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Default Re: AC LM 46-B spark plugs

I used to find them in Briggs engines when I was a kid, never saved them now I want one
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Old 01-30-2013, 02:42 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: AC LM 46-B spark plugs

LM 46-B specs: 14mm 3/8" reach. Standard plug is the AC LM-46. Heat range same as Champion J8-J, J17LM, and others. Major and most important difference - AC LM 46-B was the only spark plug with a NEON bulb built into the plug itself! These plugs were made from 1966 to 1969, only 4 years of production. I am looking for anything about these plugs, and am always looking for the plugs themselves. I know the ALF Junior takes Champion H-10 (1/2" reach) as original, but the 3/8" reach plugs will work as well.
Andrew
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Old 02-01-2013, 07:18 PM
Dempster Dempster is offline
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Default Re: AC LM 46-B spark plugs

I too found the Champion J17M was a cross for LM46. Is the B on the end of LM46B for just the 3/8" reach? I didn't have any of the plugs or crosses for it right now. Also found in Denso book that AC LM46 & LM49 crosses to Denso W14LM-U. I've had really good luck with the U groove electrode Denso plugs on natural gas irrigation engines we clean them and run until the electrode is worn off or accidently crack one taking them in or out.
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Old 02-02-2013, 06:11 PM
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Default Re: AC LM 46-B spark plugs

The LM46B* Spark Plug has a visual indicating discharge bulb (a built in neon bulb B*) that lights when energized by the spark from a coil. Like Andrew said, these were only made for a few years after the patent issue date of March 22, 1966 . I don’t know of any other makers of similar plugs .
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Old 02-04-2013, 10:00 PM
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Default Re: AC LM 46-B spark plugs

Here is a lawn mower dealers AC sales display rack I have for the AC FIRE GLOW LM46B spark plugs, with a few miscellaneous AC spark plugs. Don't ask what's in the box behind the display rack , or I might have to post more pictures... .
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Old 02-05-2013, 03:34 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: AC LM 46-B spark plugs

The actual patent is dated 1964! AC made the 'B's from 1966 to 1969. I wish I had your display! I have one like it, but the paintwork is all crackled. I have a display case, with a demonstration of the plugs operation, as well as a cutaway plug, to show how it was made. I will see if I can get my son to post it for me. The LM 46-B was sold in blister packs (single), and an 8 pack (commercial use). The commercial plugs had an unpainted base. The regulars were painted green to match the striping on the plugs.
Andrew
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Old 02-05-2013, 08:29 PM
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Default Re: AC LM 46-B spark plugs

Andrew: Here is the Patent information for the AC LM46B. Patent filed in 1962, Patent granted in 1966.

http://www.google.com/patents/US3242...242366&f=false
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AC lm46B (3).jpg   AC lm46B (2).jpg  
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Old 02-14-2013, 09:03 PM
MotorCraftMan MotorCraftMan is offline
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Default Re: AC LM 46-B spark plugs

Paul... If You in fact have Some of these Spark plugs, i would like to have One?? Or was those empty boxes, it would be great for Show n Tell the Younger Generation...., Thanks, Larry
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Old 02-15-2013, 07:59 AM
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Default Re: AC LM 46-B spark plugs

Larry: It's the same box , and I'm going to use it/them for my display . They were a L O N G time in coming my way. I wish I had extras . I keep looking for them in my flea market travels.
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Old 02-15-2013, 03:50 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: AC LM 46-B spark plugs

Paul, the patent info you have is similar to the one I have. I got mine from the son of one of the inventers. Ac was building the plugs in late 1965, but would not release them until the patent was granted. They were released for sale in 1966 and were sold into 1969, wgen the line was closed. Your box is a commercial pack box. Were the plugs in it when you got it? The LM 46-Bs were sold in 2 modes - a commercial pack and in individual blister packs. I have 1 full commercial pack, and one MT that I use inmy display case. I also have 4 different blister packs. AC tried to boost sales by changing the color of the blisterpacks, but a fight with Champion did the 46 B line in. When I bought my first AC LM 46-B, it came from a blue commercial pack. In my 45 years of looking, I have yet to run across another! I have seen quite a few red ones. As for the blister packs, the green seems the most scarce - I have only seen 3 intact. One I own, another 2 are in collecters hands. The blue blister is next in scarcity, and the seemingly most common are the 2 diferent red ones.
Andrew
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Old 06-17-2013, 02:42 PM
K-Tron K-Tron is offline
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Default Re: AC LM 46-B spark plugs

I picked up an LM46B at a swap meet for $0.25. The plug works but the neon bulb does not light up when the plug fires. Is there any way to recharge the bulb and then maybe reseal the insulator? I do not see any holes or pits in the insulator so I am not sure how the neon gas escaped. I guess the previous owner dropped the plug and something inside shifted or cracked. The plug does fire but I am bummed out that it does not glow,

Chris
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Old 06-20-2013, 03:09 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: AC LM 46-B spark plugs

The neon bulb in your plug is burned out. When these plugs were built, there was a safety gap built into the plug, that would allow it to fire, even if the bulb burned out. In the 40+ years of collecting, I have only seen 3 burned out 'Bs'. 2 are commercial, used in a stock car (mallory high voltage unit did them in), and one fo my own, that I burned, using an oil burner coil to try and make a display.

I do not know who built the neon bulb for AC, it is a direct series bulb - no resister or other circuitry in the plug. The plug can be taken apart, but you take a chance of breaking the insulator - it is a translucent porcelean and is very thin hollow and frangable. The top of the plug will unscrew counter clockwise, if it will move. The few I took apart (burned out), one had corrosoin in the aluminum cap which seized the top into the insulater (it broke), and the other came apart with little effort with a pair of pliers. The neon bulb is about 3/16" in diameter, and is about 1/2" long. It has fine copper wire conducters that are about 5/8" long, that are folded along side the bulb, so that when installed, the ends are about 1/4" apart. It is this gap that allows the engine to fire the plug, if the bulb burns out. If you get the plug apart, there is a spring under the bulb, that allows the top to compress the spring and hold the bulb in place. The bulb and spring will fall out if you can get the top of the plug off in one piece.

My current display case uses a K&W Ford Model T type coil, powered with a 6 volt battery, to light the plugs (yes plugs - it lights 8 of them, hooked in series!
Andrew
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