I'm asking a general question: the coil has a + and - which identify the secondary and primary windings. If I change the basic car from positive ground to negative ground I assume there is no need to worry about the +or - of the coil because it will still operate as designed providing the proper voltage to the distributor. In other words the distributor will receive the proper signal from the coil. Chet25441
The best explanation I've ever seen about coils is
http://mgaguru.com/mgtech/ignition/ig104.htm
The coil will work either way ….but it works best just one way
Jack Worstell jlwmaster@aol.com
Jack, thank you as this explains what I thought and I am sure if I put in a '41 coil all will be fine so long as the + on the coil goes to the distributor. My car is negative ground and the coil winding for this car was using a positive ground hookup. Chet
My reading of the article is that if the car is positive then the + terminal of the coil goes to the distributor
and if the car is negative ground then the - terminal of the coil goes to the distributor
But I'd bet that even if you were to hook the coil up " backwards" you probably couldn't tell it
driving moderately...which is what happens when driving a 77 year old car.
Jack Worstell
I agree; I just got my + and - wrong on my initial reply to you. Thanks, Chet
(?) The distributor makes the signal to fire, not the coil.
Use a neg grn 6V coil on a neg grn system and you won't have to worry. Readily available.
We're only talking ~$25. Insulation breaks down in old coils and they lose efficiency.
6V = no resister.
Used a 6 volt negative ground coil and twice was trailered in...points were stuck. Changed the coil again and same problem; not fun.
My initial and REAL problem was that the bake-o-lite through the distributor was cracked and thus grounding out on the distributor case causing the car to shut down. I corrected that problem but before I found that problem I blamed the coil and so put in the Napa coil. Now I am going back to the original coil and will install as suggested in the article above. Costly for such a small item to break down.
I had a 6V points system 54 years ago. It was so troublesome I
soon converted it to a transistorized coil driver. Thought I saw
someone was still offering such a product, still uses the points but
without the stress of coil current. If it blows up, the points could
be reconnected.
The points have a very limited current carrying capability, maybe
degraded with overseas products. As a check turn on the ignition
in a points closed crank position and check the current. A DC clamp
on meter works well. If the current is much over 4A, it will hurt
points life. The ign system does have some resistance which sets
this current. If this got reduced over time and parts changes, it
could be a problem. The other thing that will hurt points is a bad
(open) condenser. good luck, Bruce Roe