1920 Compression and ignition questions

[Mark Gregush]

Did a compression check on the 1920. 1, 2 and 4 are about 58-61. No 3 between 45 and 48. Valves maybe on No 3? With Model T's I can kinda know that between X and X the condition of the motor, but with this one I don't have a base line to work from. What would the Dodge compression range be if in good shape, same with ok but tired?

The original coil gave out so am using a MOPAR coil and resistor. The coil is getting hotter then I would like, so thinking the condenser is bad. I need to do a voltage check after I clean the plugs to see what the cold and running voltage is. I hooked the hot wire to the plus side and the spark jumps from the wire to ground so that should be right.

[nearchoclatetown]

This car is negative ground.

[Mark Gregush]

Yes

[MikeC5]

That's a little more variation than you'd like to see between cylinders but it certainly should run with that compression (I've read they should be around 50 psi).  I've done some experimenting with coils and ballast resistors.  I wanted to find a coil that would fit within the original canister so it would look correct and found a 1991 VW Jetta 1.8L coil that was small enough.  I did have to remove the outer cover (see pic) but it serves no purpose except as a mount bracket in the intended application.  I made up some jumper wires to the coil terminals from the original coil cover plate and a short high tension lead to the side post secondary output terminal on the original canister.  I also cut down the secondary post by about 1/2 inch to make room under there for a 90 degree connector.  The primary resistance on this coil was only 0.6 ohms and a test run revealed too much current going through and the coil heating up quickly to the point where the engine ran poorly.  I ended up with a 2.4 ohm ballast resistor that brought down the voltage to the points to 7 - 8 volts (12V system, positive ground) and that has been working.   IIRC, the original coil is in the 3.5 ohm ball park for primary resistance. 

Edited August 16, 2020 by MikeC5 (see edit history)

[nearchoclatetown]

49 minutes ago, Mark Gregush said:

Yes

If you have it hooked up that way then you have the hot wire on the wrong terminal at the coil. The points go to ground so the hot goes to negative side of the coil. That may be that reason it's getting hot. I would not worry about the compression. Make sure the valves are adjusted correctly and drive it.

[Mark Gregush]

I have an extra original coil that looks almost new, as soon as I can get the high tension lead plug out I will try installing it for the dead coil.

I will try swapping the leads on the modern coil and see where that get me.

Re driving; while I might take it around the block, till I get the paperwork sorted out and and insurance (and a couple of brake lights! ), not much more. Wish I could drive it. In the mean time I can drive the T to get my "OLD" car fix.

[Mark Gregush]

Swapped the leads on the coil, early results show it's cooler then before.