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Doing a tune up on my Packard. Set point gap to .020. Noticed when cranking the engine vacuum advance plate jiggles back and forth ( I have vacuum line off).

Pulled vacuum advance unit off, diaphragm is good, no leaks, but cutaway view in service manual shows a return spring. This is either rotted away or doesn't have one.

Should this unit have a return spring inside the diaphragm housing?

Searching the web, pricey part, $125 rebuilt
Has the Autolite distributor

Typically a spring and often also some shims are used to calibrate the unit to the particular advance requirements of a particular engine. Without them it will be more like an on-or-off function rather than variable advance depending on the amount of vacuum.

AS I delve deeper, it appears the spring is a replaceable unit, located behind the large fitting where the vacuum goes in. This unit does not have the spring, for whatever reason.

I can find vacuum advance units on line, but all without this fitting and hence no spring.

Anyone know what spring tension is or where to find one?

When you buy a new replacement unit, normally they would be supplied without the spring and any shims for final adjustment. Buyer would use the spring and other parts from his old unit; they establish the correct advance profile which can be verified and adjusted if necessary via shims on a distributor test bed. So the spring needs to be specific to your motor as the same advance body might be used on a large variety of motors with differing advance needs. Your safest bet is to find a complete but discarded unit from your year and model, or as close to it as you can and use the internal parts from it.

Hey Jwblazek,

In trying to find the root cause of the stalling on my '39 Six I replaced my distributor. (zero difference BTW) I was lucky enough to get a NOS unit from Packard Don, and I still have the old one. First of all, what model do you have?? Autolite, I presume? IGS 4201 or 4013?? Help me with what you need and I'll see if I can be of assistance. While I'm talking to you - how about a picture or two of your clutch return spring!?!?!?!? need the contact points of where the spring hooks to. Chris

Hey Chris
It is an Autolite, not certain of model, either a IGS 4013 or 4201. Autolite catalog doesn't help much either, but looking at the breaker plate assy, the catalog kind of points to the 4013 model

What I need is the specifications for the vacuum advance diaphragm spring located in the housing, between the diaphragm and where the vacuum enters. Not certain you want to pull yours apart to look, measure etc.


My 39 is unrestored and most is original, along with the 80 years of grease, which I am tackling one step at a time.
The clutch spring hooks onto the bracket next to where the adjusttment nut for the clutch is and then takes a long route to a hole in the frame rail near the master cylinder "U" mounting bracket. 2 pics attached, let me know if you need more

Feel free to drop me an PM if you need more info or we can continue here

Are you certain it is a spark issue and not a fuel issue? Not certain of the condition of your vehicles wiring, this one has a lot of original cloth wiring that is falling apart and I had a similar issue. I rewired the coil and distributor, and many of the wires under the dash when I wood grained it. I am using era correct cloth covered wire and problem went away

If you are near the SF BAy area, drop me a line and you can come see the car

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Jblazek, Thanks so much for the pics!!! I don't remember the spring attaching to the clutch fork like your photos show. I thought of that and tried it that way and then wondered why there is a return spring on the throwout bearing? That big spring pulling that way would make the little one totally redundant, wouldn't it??? And your pics show that u-shaped bracket that the clutch pedal rod connects to; I could not believe the wear on that bracket AND the rods leading to it!! I didn't measure it, but I'll bet the slack in all the connections combined to take up 3/4 of the clutch pedal movement! I'm looking for some good used pieces to replace them and notwithstanding, will have to have mine built up and machined. Definitely something worth checking out on your car, as you say, its mostly original, as is mine. 80 years of wear (and grease!!)
Anyway, I'll have a look at my spare distributor; I believe mine is a 4201, but I'll go out on a limb here, and say that I think either the 4013 and the 4201 are pretty much interchangeable. If I'm wrong, someone will jump in and correct me. Irrespective, I think (again, not positive) that the vacuum pots are the same for both units. Once I have a look, I'll come back to you - probably PM you. Thanks again for taking the time to shoot and post the pics - much apprec. Chris

The Autolite catalog shows they are interchangeable

AS for the wear on that bracket, you are correct! I pulled that U-bracket off, holes were greatly elongated, almost twice the size they should have been and the rods going into the holes were also worn. I welded over the holes, ground it flat and re-drilled then reamed the holes. I bought one of the rods from Max Merrit or Kanter. When I was done, an entirely new clutch feel, almost a full pedal as spec'd in the manual. Prior to this, clutch pedal would not fully disengage the clutch!

Good luck !

If you need more pics of anythiing, let me know. Car is currently up on jack stands as I am redoing a lot of teh wiring on the left side of the engine compartment and the overdrive solenoid.

Good Luck !
john