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Hi all,

Was replacing the dual point plate with single point variety from Pacific NW Packards. Found that the smaller mechanical advance spring on my distributor is simply missing. Any advice on where a guy could buy a new one without purchasing an entire distributor body?

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Problem is without knowing the specs it will be hard to get a match and even if you do find an original Northeast spring there may be a difference in springs because of different advance curves one distributor to another.

You might measure the wire diameter with a micrometer and get the length and diameter of what you have to find as close a match as possible to what is there. McMaster has some precision extension springs in packs of 3. Some look like they might do the job. Change the pair or maybe try just one and then have the dist checked with a machine and adjusted to get the proper curve.

Sherlock, without a Northeast parts list to check, you have to accept that the two springs may not be identical; that's often the case with centrifugal advances. Unless you can find the correct spring it really may come down to setting the distributor up in a test machine and finding an appropriate spring to give the correct advance curve by trial and error. That's a pretty unattractive prospect so in the end you may want to send the unit to one of the distributor rebuilders who specialize in Northeast units.

Thanks for the info everyone.

The missing spring is definitely different than the one still there and I assume there is no longer extant any Northeast parts list that would properly identify the specs of that spring. So it's either send it off to a pro or try to match the spring as best I can.

I would think if I can specify the spring material, its diameter and length as well as the wire diameter, I should be able to get a close match. There are a number of spring materials available today: music wire, oil tempered chrome silicon, stainless steel and Elgiloy. The springs don't look like stainless steel. My guess would be the material is music wire.

In the meantime, does anyone have an opinion as to whether the missing spring would affect the engine's ability to start?

The two springs in the 740 distributor are different. If you cannot find a correct spring I will strip mine and measure the spring so you can have one made.
I recently had a problem with my 740 that is relevant to this question. The car was running normally and suddenly stopped as if the ignition had been switched off. It then failed to start after many attempts over a period of time with no sign of it ever firing. After checking all of the basics I discovered that one of the springs in the distributor had come off and had been mangled by the weight. I doubted that this would have stopped it from firing because although it would have over advanced the spark for starting I had been manually retarding the spark which I thought would compensate.
However, it had to be fixed and my local source for springs did not have a standard one that was close but to my surprise they said they would make one. They measured the wire diameter, number of turns and the distance between the pegs in the distributor then made the length so that it had a little tension. It may not be identical to the original but it would be close.
After installing it in the car it started after a fair bit of cranking and after clearing the excess fuel from all of the previous start attempts, it settled down and ran normally.

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David, thank you for your kind offer. I may be able to source the correct spring if I have the proper specs: diameter, length and wire diameter. If I cannot source it, I should be able to have one made based on that data.

As you know I'm having trouble getting the car to start and thought changing the dual points for a single point plate might be the answer. That's when I discovered the missing spring. Now I wonder, as that was apparently the reason your engine suddenly died and would not start again, if I have the same problem. Still, like you, I don't understand how the missing spring would stop the engine from even firing at all.

If you like a challenge, you might want to try your hand at making the spring. I've tried my hand at this, it's actually fun.

http://www.deansphotographica.com/machining/projects/springs/springs.html

As to the lack of spring having an effect on starting, it shouldn't be a problem if the weight stays in it's inboard position, as the centrifugal advance doesn't come into play at those low rpms.

I will remove my distributor over the next day or two and measure the spring.
In my case the spring got caught under the weight and dragged it into the fully advanced position where it stayed. I am still surprised that it stopped the car but the fact is I was only able to start the car once the new spring was fitted.

A couple of degrees of change in a timing curve is pretty inconsequential, though if the engine pings, it should not take much adjustment to cure (Unlikely with your low compression?). Anyone with an adjustable timing light should be able to tell you if things are in the ballpark. I have some springs from a V8 Autolite dizzy, free for the asking.