I'm cheating in this area

The Model T Ford mechanical and electrical system remained largely unchanged during its production run from late 1908 through 1927.  There were good improvements the ignition system during that time, the most important, in my opinion was the change to the standardized "KW style" ignition coil in 1913.  

The Model T ignition coil box, contains four coils that "buzz" and the electrical spark to each cylinder.  Ford bought these coil box assemblies from several suppliers before 1913, including Heinze, Kingston, Jacobson-Brandaw and K-W.  Each company's ignition box contained their own particular coil design, which were not interchangeable with the other's.  Lacking interchangeability is a manufacturer's and customer's nightmare.  

For those who have never seen a Model T coil, it is probably the best example of "steam punk" technology on the car.  It is a wood box filled crude looking electrical parts all encased in tar.  They take the low voltage alternating current from the car's built in magneto and converts it into a high voltage spark. The figure below shows the mysterious inner workings of the Model T coil box.  When operating, they each make a buzzing sound as the point open and close quickly.  These coils are enclosed in a box on the firewall and it sounds like a thousand angry bees trapped inside.

K-W coil used on all Model T's from 1913 and on

The pre 1913 coils tended to be finicky, making the car more difficult to run properly.  The big improvement was made by the K-W company with there new coil design, when they incorporated a "cushion spring" on the points mounted on the top of the coils.  The improvement was dramatic enough that Ford switched to this style of coil for the rest of the car's production.  A secondary, but important, benefit was that the cars now had a common size ignition coil that the customer could easily replace with a new one from Ford.  Eventually Ford even built these coils inhouse under license from K-W.

The 1911 Model T that I am restoring was originally equipped with the early style coil box.  Which is lost to history, because the first or second owner replaced it with a later year coil box that used the K-W coils.  Smart move.  The previous owner decided to correct this and found a used Heinze coil box that was correct for the car.  It must have worked well enough for him, because it was still on the car when I got it.

Heinze coils that came with the car

I was concerned about using the original style coils for the reasons given.  I like how the later K-W coils work, and I have experience rebuilding and tuning them.  There was only one guy in the USA who worked on the old style coils, and he unfortunately passed away a few months ago do to an apparent complication with the Covid booster.  He gave me some tips on how to check to see if the coils were good, and the Ohmmeter test that he suggested showed that all of the coils had a short in the windings, indicating that major surgery would be required to make those coils functional again.

I decided that this was one area that I was going to cheat on the restoration.  The Model T parts suppliers sell replica coil boxes that look like the early style ones, but are sized to accept the "modern" K-W ignition coils.  I got one of those boxes along with a new switch box that allows the driver to run the car on the engine's magneto or the standby battery.  Normally the battery is just used to energize the coils when starting the car.  Otherwise the driver needs to turn the crank at sufficient speed to generate the 4 1/2 volts needed.  This is really not a problem if the magneto system in the car is functioning well.  I almost always start our 1915 Runabout with the switch set to magneto.  The cars did not even come with the optional battery from the factory.  

The picture below shows the completed box with four early brass topped coils that I restored.  These coils were graciously given to me by Erik Larson, a Model T coil rebuilder in Idaho that rebuilt the coils for our Runabout a few years ago.  Since that time I have learned how to rebuild and tune them myself.

Replica Heinze coil box sized to accept K-W coils

The last picture shows a comparison of replica versus original Heinze coil box.  You can see that replica box is slightly larger.  The ignition wire attach locations are dimensionally the same, so no change is required for the firewall.  You may have noticed that the stain color is different.  I used Laurel Mountain Forge cherry stain, which is the most recommended stain by T restorers to match the original stain used by Ford.  My observation is that it does match really well the stain found on the original firewall that came with the car.  The original Heinze box may have been re-stained at some point.  Either way, my new coil box is going to work better and match the firewall!  

So, yes, I am cheating on the ignition system for this restoration and I am glad that I am!

Comparison of the original and replica Heinze coil boxes