What is the correct condenser rating?

[pebo va]

I recently had several condensers tested for my 1949 stock flathead and they all registered .24 Microfarads. Is this a good reading? If not, what should be the correct reading for a "good" condenser?

[petehoovie]

Here's a good thread on the subject > https://www.fordbarn.com/forum/showt...denser+reading

"Almost all automotive distributor coils use a 0.25-0.29 microfarad capacitor. The operating voltage rating should be no less than 600 volts DC. There are now capacitors available in the 0.25 microfarad range rated at 630 volts AC. Since the AC peak voltage is 1.4 times the nominal value these capacitors are actually 880 volt DC capacitors making them ideal for ignition use."

[woodiewagon46]

If you are interested, there is an in-depth article on condensers in the 2014, Sept./Oct. issue of the V-8 Times. It's way over my head, but the article states that '49 thru '53 Fords should .22 to .28, so your .24 is right in the ballpark.

[Kube]

I recall testing done and it was determined that 30 was the optimal. Since then I have installed 32 and have found it amazing at how well the cars run.

[pebo va]

I found the article by Frank Scheidt in the V-8 Times and .24 mfd is right on.
Many thanks!!

[tubman]

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It is really dependent on a number of factors : the coil and engine speed primary among them. The only way to make sure that you have the optimum capacitance is to run the entire system at the desired RPM and watch it on an oscilloscope.

In the real world, it doesn't make a heck of a lot of difference. When I was developing my "Trash Can" condensers, I tried a lot of combinations. The engine ran fine with values as low as .047 microfarads. The main concern is point life, and you have to get way out in left field for that to be a major concern. Anything between .20 and .50 microfarads should be fine. (I have some large Mallory "Bus Capacitors" that look like a larger silver "Trash Can" that are rated at .46 microfarads.)

More important than the actual capacitance is stability over a large range of temperatures and voltages and longevity. I have seen an old Ford publication that stated that too low a capacitance would accelerate point wear, while too high would compromise performance.

[Kube]

Originally Posted by tubman

It is really dependent on a number of factors : the coil and engine speed primary among them. The only way to make sure that you have the optimum capacitance is to run the entire system at the desired RPM and watch it on an oscilloscope.

In the real world, it doesn't make a heck of a lot of difference. When I was developing my "Trash Can" condensers, I tried a lot of combinations. The engine ran fine with values as low as .047 microfarads. The main concern is point life, and you have to get way out in left field for that to be a major concern. Anything between .20 and .50 microfarads should be fine. (I have some large Mallory "Bus Capacitors" that look like a larger silver "Trash Can" that are rated at .46 microfarads.)

More important than the actual capacitance is stability over a large range of temperatures and voltages and longevity. I have seen an old Ford publication that stated that too low a capacitance would accelerate point wear, while too high would compromise performance.

Thanks for the easy to understand lessons here. I knew about the oscilloscope but didn't realize there many other contributing factors.

[40cpe]

Originally Posted by tubman

I have seen an old Ford publication that stated that too low a capacitance would accelerate point wear, while too high would compromise performance.

For a dunce like me, which end of the range is "high" and which end is "low"? Is it like gearing where the high number is low geared?

[tubman]

Nope; the .047 micro-farads I tried just for the hell of it was really low, and the bus capacitors (at .46 micro-farads) are really high. While most currently available automotive condensers are in the mid 20's, the original Mallory "Trash Cans" were .36 micro-farads. I believe they did this because two sets of points and higher revs required higher capacitance, just as a heavier vehicle requires heavier rated shock absorbers.

[40cpe]

Originally Posted by tubman

Nope; the .047 micro-farads I tried just for the hell of it was really low, and the bus capacitors (at .46 micro-farads) are really high. While most currently available automotive condensers are in the mid 20's, the original Mallory "Trash Cans" were .36 micro-farads. I believe they did this because two sets of points and higher revs required higher capacitance, just as a heavier vehicle requires heavier rated shock absorbers.

Thank you

[frnkeore]

A question that comes to mind, after reading the range of mfd is, has anyone tested the voltage output, with different mfd's and point gap settings.

For instance, with a higher mfd, can you run the points closer and pick up some dwell?

[tubman]

Originally Posted by frnkeore

A question that comes to mind, after reading the range of mfd is, has anyone tested the voltage output, with different mfd's and point gap settings.

For instance, with a higher mfd, can you run the points closer and pick up some dwell?

I wouldn't think so. Point ignitions are a compromise between gap, dwell, point erosion, and spring pressure. I believe the old engineers got them optimally balanced early on.

That's why they developed electronic ignitions.

[rotorwrench]

Everything was designed for a purpose in the older ignition systems. Evolution of the systems made things much less complicated. The old Mallory/Ford design distributors were designed to work the way Henry wanted them to. Henry wanted the coil, breaker set, and distributor all on one package that would require little maintenance and there for chances of it being messed up by a person than wan't familiar with it. The coil evolved from the one that was designed to Henry's specs to one that was better for mass production and reliable function. This is where Mallory came in. The coils had to be specially made to fit the helmet distributors. These coils are different than the can type coils that were used on the Model A and eventually came back into vogue with the Load-O-Matic system in the 8BA era. The Mallory coils were matched to the 0.3 micro farad type capacitor by design. The can type coils were matched to the 0.24 micro farad capacitor by design. There is a formula that coil designers used back in the day to calculate what worked best for each coil design.

Henry Ford wanted the Helmet type distributors on his V8s and Marion Mallory Sr was the guy that helped him to develop it for mass production. Emil Zoerlein was the first of the Ford engineers tasked with setting it up the way Ford wanted it so he has to get some credit too but the evolution came from Mallory. It had automatic advance, duel points for better dwell time, and a vacuum brake for load spark timing control all in one neat simple package. Henry Ford and Marion Mallory were good friends and Henry gave him a lot of the subcontracts to manufacture his ignition components clear up till after Henry died in 1947.

Holley took over in the 8BA era with the combination of carburetor and ignition system. Mallory went on to the aftermarket and performance ignition systems. Mallory is now part of the Holley performance group.