My 56 Ford Fairlane developed a stalling tendency recently when clutching to take off.
It was most noticeable after the engine was hot, then shut off 5-10 minutes to heat soak, then re-started again to journey on.
I found and fixed the problem and judged it unique enough to share.

There were two contributors.
The minor one was a plugged primary barrel air ingress orifice starving its aerator
tube – most likely caused from setting over a year with a tank full of wishful premium gas.
Unplugged, it wasn't didn’t fix the stalling.
The major culprit turned out to be a near 4X increase in ignition ballast resistor resistance from internal corrosion behind its perforated snap on cover.

By way of review, my collection of 12V Ford oil filled canister coils & ballast resistors all originally measured 1.5 ohms primary resistance
(tip: don’t forget to subtract your multi-meter probes resistance from these component measurements else you’ll get a false high result).
These component values limit my ignition point current flow to 4 amps
(12V / (1.5 + 1.5ohms))when new,
a decent Kettering ignition system balance between point contacts wear and spark strength.
In my stalling scenario, the resistance of the ignition primary coil had dropped to 1.2 ohms while the ballast resistor had increased to 5.7 ohms
- dropping the distributor ignition points current down to near 1 3/4 amps at cold idle and even less at hot idle given wire resistance increases temperature.

My safe WOT redline is 5500 rpm. I try to enjoy its thrill most every outing (yes, old habits die hard).
I’m amazed that such a low ignition current still adequately fired the Y-Block to redline, cold or hot.
It took a good heat soaking and clutching to take off to finally kill the fire.

The fix; a new coil and resistor. So I went coil hunting.

Oil filled ignition canister coils are very small transformers.
Transformers contain a special heat transfer/insulating oil (PCB) to transport coil heat through the containers walls
to the atmosphere to thwart coil wire insulation heat failure,
resultant wire shorts and resistance degradation.
Transformers are designed to operate vertically up right to insure the coils are fully submerged
in oil as well as to achieve optimum length wise oil circulation over the coils for maximum coil heat transfer
to the atmosphere at minimum risk of leaking toxic PCB.

Horizontally mounting an oil filled ignition canister coil risks uncovering some of the primary coil wire
with resultant exposed wire insulation damage, wire shorts, lowered coil resistance and increased ignition point contact wear.
It also inhibits optimum oil circulation and coil cooling thus elevating primary and secondary coil temperatures
with the same family of risks as exposed coil wire.
And it risks oil leakage, the most exposed wire scenario and shortest coil failure path.
Ford mounted Y-block ignition coils horizontally.
This may explain why my original 1957 yellow top ignition coil & two subsequent aftermarket replacements
have lost about 20% of their primary & secondary coil resistance.
Nevertheless, I’ve never had a Y-Block ignition coil fail to get me home in 58 years of Y-Block enjoyment.
That was with ignition coils made in the USA. That’s history now.

From now on, I’m treating all aftermarket oil filled ignition canister coils as foreign made due to strict USA EPA PCB oil regulations.
I won’t buy an ignition coil I can’t physically handle, shake and measure its resistances at the parts counter.
If it doesn’t slosh some, I say it’s empty and junk rather than oil filled.
I won’t internet source one due to return shipping cost.
I “googled” “best oil filled ignition coil”.
It led me to the Master-Pro 2-5195 oil filled canister coil (O’Reilly brand).
I measured the resistance of 3 different coils (3 different stores in my area).
All had 1.5 ohms primary resistance, secondary k ohm resistance in the low 10’s (better than my spares),
cost under $25 and could be locally sourced same day.
I bought one.
If I did another search a year from now, it might be a totally different choice.
That’s the way the market is today.
Nothing stays around very long.

Just because I bought one doesn’t mean I trust it to get me home mounted horizontally.
No way.
I mounted the new ignition coil vertically up right, in the void space in front of the block, above the generator,
on a home fabricated bracket anchored to the nearest intake manifold bolt and shared top water pump-generator
bracket bolt for maximum air cooling.
Same for the replacement ballast resistor.
But, I’ll now carry an older take off of each and a multi-meter in my trunk as insurance.

 Since the relocation is permanent and I hate unsightly wiring, I forged ahead and updated the engine bay wiring as follows:

1)      A new 24" long bulk BWG copper core ignition wire (p/# MW11) was terminated with the old coil lead
wire ends and boots to make a new coil lead with a meniscal resistance of 1.4 ohms send ignition coil spark to the distributor.

2)      The coil end of the solenoid I terminal coil start feed wire is now spliced at the firewall to the 12V ballast
resistor run feed wire for a cleaner firewall look.
This splice extends the 12V ballast resistor run feed wire current along the former resistor start feed wire to the
solenoid location where the I terminal connector was clipped off so I could splice and further extend the 12V run
feed current to the top terminal of the new ballast resistor, now mounted upright on top of the generator's parallel cross brace.

3)      A new 12V start feed wire was made to connect the solenoid switch I terminal to the front mounted ignition coil POS post.

4)      A new wire was made to connect the ballast resistor bottom terminal 6V output to the front mounted ignition coil POS post.

5)      A new wire was made to connect the ignition coil NEG post 4 amp output to the distributor points input
post via passage beneath the intake manifold, for a bit cleaner engine look.

6)      The former rear mounted ignition coil NEG terminal connection to the in-dash tachometer and overdrive
kick down ignition grounding wire are now relocated to the distributor input terminal for neatness.

I test drove the car after the above changes. I’m pleased to report thisY-Block runs as strong as ever again.