0Ba distributor condenser question

[3twinridges]

We used a NOS 0ba distributor in our 52 F1 8BA build. The engine runs strong but at idle I have a very slight intermittent miss, almost like the engine stumbles for a second and then recovers, it’s barely noticeable but on that miss, the vacuum gauge dips slightly.

Thinking I have an ignition issue I tested the condenser. It tests out at .286 microfarads which according to van pelts site is out of spec, it should be between .21 and .25. Think that condenser is bad and causing the slight miss?

JB

[supereal]

Your'52 truck used the 7RA-12300 condenser, the same as the passenger cars of the same age. Chasing an intermittent miss is tough.. It could be a faulty plug wire, a misfiring spark plug, or a sticking valve. It doesn't sound like a bad condenser in most cases. I would run a compression test to see if you have a low cylinder with a varying reading. That would cause the vacuum gauge to flutter. Failing condensers are fairly rare. I carry a spare in my "road kit". I put the condenser in a large pill container and have clip leads attached.
In the event of condenser problems, you place one clip lead to the coil output to the distributor, and the other to ground. Over the many years, I have used this once, but loaned it to others to help get them home. The small difference in your test is too low to matter.

[Terry,OH]

Check the ohmage of the plug wires and both end of each wire including the coil.

[tubman]

If the condenser is not seriously affected by heat or vibration, the .286 micro-farad reading should not be a problem. The Mallory "trash cans" were .36 micro-farads and they worked fine with stock distributors. I have spent a lot of time with condensers, and will tell you that anything from .20 to .40 will allow the engine to run fine. There MAY be a problem with slightly accelerated point wear, but for running problems with your vehicle, I suggest you look elsewhere.

[3twinridges]

Today we got around to doing a compression test. I did the test with engine cold, and most cylinders were around 95-100, but #1 and #5 were at 85. Digging a little deeper, we put a leak down tester on number 1, and I only had about 7% leakage so I don’t think I found any smoking guns there. I did pull the condenser and test on the bench and the reading was .30, I put another condenser in that tested out at .24, and the engine seemed to run smoother without the slight stumble. The vacuum gauge was pretty steady around 20”, slight fluctuations, but no more that .5” or less occasionally.

I tested the plug wires with a champion plug wire tester and #5 seemed suspect intermittently, I may change that wire to see if I have more consistent flashes.

The plugs all look good, no evidence of fouling.

JB

[tubman]

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What kind of plug wires do you have ? Solid core or something else?

[Crankster]

Condensers (capacitors) are always tested at their rated voltage, in this case about 500 volts DC, a digital ohmeter or capacitor "checker" can't do this. Ignition condensers are also tested when hot, or at normal operating temperature. The capacitance itself is only part of the story. If I was running a points ignition I'd definitely want to have any NOS condensers (and spares) pre-tested at their rated voltage before use, or secure a modern high voltage replacement.

[3twinridges]

I know bud, all I had on the shelf was NOS. I have a couple of new ones on the way from NAPA, for inventory and swapping out the one I just put in.