What is your opinion on 1950-60's built KW Model T coils?
1914--1927 better ?
Flat core verses wire core?
Whitch has the best Q ?
Does one have a better primary or secondary?
Thanks for your opinions
Although they are not as well made as Ford & KW 1914-1927 coils, the 1950-1970's "KW" trade mark stenciled coils (not made by the original KW Company) can be made to work very well. I have rebuilt many of them for customers.
Ron the Coilman
I have a set of KW coils bought in 1962 from a supplier. I had them "tuned" in 1985. They produce a great spark. I "fuel" them with a 12 volt battery for starting.
Typically the secondary on the flat steel core models has a much higher DC resistance often on the order of near 10K ohms. Since I doubt that they have 3 times the inductance to go with that resistance, the Q would be lower but Q isn't the only thing of importance since longevity of the coil itself is equally important. I don't like those winding and don't use them because they appear to be made with finer wire on the secondary and that can mean breakage since the finer the wire the more frail it is. I just don't want to go to all the work of re-manufacturing an all new box and hardware only to have the winding fail down the road. Just not enough history on it for me to want to take the chance. Your mileage could vary.
I have a 1962 set in my car which I rebuilt myself. They are better made than many coils I've seen and work great.
In a spark coil the secondary is essentially unquenched (allowed to spark) which makes the q factor for the secondary somewhat unimportant. The q factor of the primary, however has a direct bearing on the efficiency of the coil. In my experience, the 50's laminated core coils are very good in regard to q-factor.
Here is a link to a Montana 500 newsletter where I tested the q-factor of various coils.
Interesting article Tom C thanks for the link.
Thanks Tom I knew you had done the article just hadn't dug through the Montana 500 archives deep enough.