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TR2/3/3A "Big" ignition coil

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CJD

CJD

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Moving up the ignition...

I've been cleaning what I have and referring to the diagrams for the big three suppliers, but I am still confused on a few points about the ignition coil.

The judge's guide says all the early cars had the "big" coil. What is the difference between the big coil and the later coil? Also, did the early coils use studs and nuts for the low tension connectors...vrs. spade connectors? Finally, how does the "screw nut" high tension lead work?

Thanks!
 
The "big" coil was taller, and I think maybe a bit larger in diameter than the later coils. Yes, studs & nuts for the low tension terminals. For the high tension, strip back about 3/16" of the insulation, thread the wire through the nut and copper flat washer (only the stripped end fits through the washer), then fan the strands out and solder them to the washer.

The terminals were marked "SW" and "CB". For original positive ground, "SW" gets the white wire from the harness, and "CB" gets the wire from the distributor. But switch those if you've converted to negative ground.
 
CJD said:
Finally, how does the "screw nut" high tension lead work?Thanks!
Click to expand...
The "screw nut" requires, in front of it, a small brass round washer with a small hole in the center through which the wire strands from the high-tension lead feed and then"splay out" radially. Screwing the nut into the coil then clamps down those splayed strands under the brass washer, hopefully making good contact inside the coil. Easier to visualize than to explain, but I haven't got a picture handy!
 
Aaah. So the nut was for solid core wire. The coil the TR2 came with has the nut style coil, but the PO used a push-in style wire with carbon core. Now I understand...Thanks guys!
 
The stock distributor cap is also intended for solid-core wires. Just like the coil, it will kind of work with carbon core, but does better with solid.
If you want to stick with the carbon core wires, there is a cap that will work, designed to take the push-in connectors. I think it's original to MGB.
 
Here's a pic of an original (8/59) positive ground coil. HTH!

 
Thanks Randall, Kevin...

I just got new wires from Moss, the only ones they sell. I'll look at them today to see which core they are and make a decision from there. My only experience with solid core wires is when my buddy in highschool used a set on his Chevy. All the radios within a half block would go out every time he drove by. On my TR3 I never even looked at the wires. They were in good enough shape that I just cleaned them in the cap and put them back on.

It's funny that, as simple as these cars are, there is always more to learn!
 
Some years back I bought a 'universal' ignition wire set from CARQUEST that was solid core and offered for V8s.

I think I have made 4 TR sets from that kit -- so far.
 
I dug through all my bins and found 4 total Triumph coils. Three have spade low tension connectors. One has studs and is 3/8" taller than the first three. So, how tall is "tall" for the large coil? Is 3/8" about right, or is it significantly taller than that?

The Moss wires are solid, as were the 3 sets I found laying around, so I assume solid wire was standard on these cars. I also found the small brass washer you guys were talking about, hidden under the nut for one coil. I'll use that to make the Moss press in coil connector into a nut style.
 
Not counting the nut, my "tall" coil measures a bit over 6-3/4" high overall. By comparison, a modern "Lucas Sports" measures about 6-1/8", and an Accel Super Coil is 6" even.
 
I was thinking my coil was the taller coil and it measures only 3/8" taller also. Randall beat me to my post so I went out and measured again. My 3/8" measurement was for the body of the coil only, overall it measures as Randall said 6 3/4"
 
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