Bob,
I think Fred K. is absolutely correct in that it far to early
to start major work. Earlier I mentioned the compression check, it is vital that the throttle be wide open during the test.Also,since there was a strong backfire it might be wise to remove the air cleaner and look down the throat of the carb to make sure the throttle plate is opening when the
test is run. It would be interesting to know the pressure in
each cylinder 1-6 or 1-8 the pattern of pressures might be a clue, for instance two very low pressures next to each other
might indicate a bad head gasket, this could be from a head
gasket that was not retightened after running a while.
I think HH56's idea of sticking valves also makes sense
I think I noticed the work was done about a year ago, has the car been sitting since then? Many times the better shape the
engine is the more likely the valves will stick, Packard had some problems with this even with new cars in storage.

It has also been mentioned many times that good connections and battery voltage are CRITICAL on a six volt system.
Are we sure the solenoid was the problem?
These engines were among the very best available.
Sorry to be so long winded but we all share a sincere desire to help you with your problem.
Jim

I don't think the compression would be even across all
cylinders if timing chain was broken. Also some cylinders would be burping back into the intake manifold.
Also no spark if cam isn't turning.

I would like to ask one question, did the mechanic
open the throttle wide when checking the compression?

Wouldn't the 225s cause the speedo to read higher?
Aren't they smaller in diameter?

Have you checked the water distribution tube? Also. are you
sure the heat sender is the correct unit and is functioning
correctly?

First off, beautiful work on your casting!
I don't have the personal knowledge on the louvers but, have been watching with intense interest as my son and I want to do something similar with a 1707, we know it wasn't available
but we are approaching from a "what if someone during the summer of 39 had said I'll order a twelve if" and they had been willing to modify the same units they were readying for
the 18th series.
JSL

You might pull the distributor cap (leave the wires on) and look at the inside for moisture between the terminals.

For sure about the Safety Flex, the thing that caught my
attention was that the other side was tight.

Does the wheel-hub have play if you grasp the top and bottom
of the wheel or just side to side, if just side to side
perhaps it is play in a tie-rod end etc.

You are correct, my car was a flat windshield versus the
"wraparound", that little engine could run flat out for
long periods and be little worse for wear. Don't ask how I know.