Doc.......you do know that there are 2-different kinds of ignition systems used on the 8N-Engine, don't you? The weird 4-nipple frontmount with squarecan coil and the more familiar 5-nipple sidemount with roundcan coil. BOTH take different solutions to the 12V conversion conundrum.
But FIRST consider WHY convert to 12V, 2-reasons; brighter headlites and sprayer accessorys ...or... worn engine that needs faster turning starter motor to start. 12V on 6V starter motor really turns FAST. Because it just takes a couple of rumpas to start on 12V, yer starter motor nebber gitts chance to gitt hot.
Now to the ignition coil. First coils don't work on direct current (DC) as in BATTERY. So you interrupt the DC with points (mechanical switches) which makes the coil transform the low volts DC to HIGH VOLTS (17,000v) sparkies. Them lazy sparkies JUMP across the gap of yer sparkplug and guess what??? The gas mixture EXPLODES and drives the piston down to turn the crank.
Remember, in 1939 batterys were NOT die-hards, they died eazy. So enter the "infamous ballast resistor". It is a temperature sensitive resistor that changes resistance due to its own internal temperature. According to Ohms Law, the more resistance, (as in internally HOT) the less the current in the coil. So when you were starting a COLD engine, the COLD battery could only supply a little bitt of sparkie power. That is when the "brilliance" of Ford's infamous ballast resistor came into play. When COLD, less resistance and more POWER fer the sparkies trying to ignited a cold wet gas mixture on a slow turning engine. As the engine warmed up, so did the ballast resistor and reduced the amps to the weaksister squarecan coil. Unfortunately, the squarecan coil insulation tar MELTS when over heated and causes weak sparkies. (even when cold again)
BOTH the original 6V and the modern 12V squarecan frontmount coil require the MANDATORY "infamous ballast resistor"...NO ARGUE!!!
Now lets talk about the 5-nipple roundcan coil. It is OIL COOLED. (and yes it gitts HOT to touch) The el-cheapo Bubba conversion uses a ceramic 12-to-6V conversion resistor and the original 6V roundcan coil. We recommend the NAPA IC-14 roundcan coil that NEVER needs a resistor to operate on 12V. Understand?
Do you know what happens when you use either the 12V squarecan coil or the IC-14 on the original 6-volt battery??? WEAK SPARKIES!!! Ittz the LAW, Ohms Law. ........HTH, Dell, yer self-appointed sparkie-meister
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Today's Featured Article - Oil Bath Air Filters - by Chris Pratt. Some of us grew up thinking that an air filter was a paper thing that allowed air to pass while trapping dirt particles of a particles of a certain size. What a surprise to open up your first old tractor's air filter case and find a can that appears to be filled with the scrap metal swept from around a machine shop metal lathe. To top that off, you have a cup with oil in it ("why would you want to lubricate your carburetor?"). On closer examination (and some reading in a AC D-14 service manual), I found out that this is a pretty ingenious method of cleaning the air in the tractor's intake tract.
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