Yes, that's the pump I have, thanks Charley. I did find the O-ring from Tee Bird Products, cost of $1.25. Rather than try to match something up, I called them and ordered it.

I've run into a couple of issues with the '57 distributor, but first I want to dig into it some more tomorrow. Right now I gotta get some sleep. Thanks guys.

OK, a couple of concerns I want to run past you guys...

1) The distributor cap is NOS, Motorcraft, with the #1 plug hole demarcated on the surface, and has a cutout along the rim to allow for the fit of the vacuum advance module. But the cap isn't a good fit--it isn't snug to the distributor body. And if you apply a little manual torque to it, the engine starts to run rough. Anyone had any experiences like that?

2) With the vacuum advance disconnected and plugged, I set initial timing at idle (550 RPM) at 10 degrees BTDC as a starting point. With engine revved to 1500, the centrifugal advance shows 25 degrees (that is, the original 10 + 15 more). Then at 2000 rpm, it yields 33 total. I know I need to check it at higher rpms as well, but it's hard because I'm by myself right now. Anyway...are those numbers a bit high? (This engine has a higher lift cam and ported C heads, and I do want a good spark advance. But those readouts are before vac.)

3) When I connect the vacuum advance line, the engine quits immediately and burps back through the carb. I have now pulled the advance module off the dizzy and will take it apart. But why would it kill the engine entirely? The diaphram is supposedly brand new, and it does hold when I suck the air outward.

Any words of wisdom are appreciated.

Sounds like you are connecting to "live" manifold vacuum at idle - and the combined 10° initial plus the vacuum - plus it probably speeds up(?) - all of that is making the engine "over-advance".

If that is the case - Try plugging the vacuum line into a "ported vacuum" source - that port should only give a vacuum signal as the throttle blade leaves the idle position.  

When you rev the engine with mechanical advance alone - where does it stop advancing when the initial is 10°? Your orignal tests seemed to show the full advance was 33°-10° = 23°. Is that all of it or is there mopre if you go higher in rpm? 

 
 Steve Metzger       Tucson, Arizona

The cap can rotate some when it is clamped down but there should be some resistance. Under normal operation, it should not turn on its own. So, if the cap just flops around when it's clamped down, there is a problem. If it stays put you should be good.



I think your timing is advancing faster than it should. You are getting about 1 degree of advance per 63rpm, that puts you at 39 degrees of mechanical advance at about 3000rpm (49 degrees total), assuming that the mechanical advance does not stop advancing before that point (it very likely does stop advancing before then). I think you need to slow the rate of advance so it's all in no sooner than 3000RPM and possibly limit it to about 24 - 28 mechanical with 12-14 of initial. From there you will be able to fine tune.



Not sure about the vac advance.


Lawrenceville, GA

Hi Steve,

I connected the vac line to ported vacuum at the carb. It's a Demon carb and it has the little brass vacuum ports just above throttle plate level. That's what's confusing the crap out of me. Car won't start with this line connected.

<When you rev the engine with mechanical advance alone - where does it stop advancing when the initial is 10 ?>

My sense is that it's not finished mechanically-advancing when you exceed 2000 rpm, although that's as high as I got. I still need to compile more specifics, but it's difficult to do this alone. I need to rig up a temporary throttle arrangement.

Edit: I did take apart the vacuum advance module. It's perfectly fine, holds it's vacuum...appears to be brand new as the seller indicated.

Charlie: if further tests confirm that the mechanical advance is advancing too much, the way to address that is to try new springs, correct?

Too much advance would indicate too large of a discrepancy of spring strength between the two?

The springs will change the rate of advance. To change the amount of advance, I believe, will require that you either grind the slots to get more advance or braze or weld the slots to get less advance on that particular distributor. I'm more familiar with the Motorcraft distributors.


Lawrenceville, GA

Joey - If you are using the ported vacuum port, it should have no vacuum at idle with the throttle blade very near closed. So attaching the line - or detaching it - at idle shouldn't have an effect on the engine speed.

The Autolite distributor would have the "slotted" type of centrifugal travel stops in the upper rotor shaft (has the cam above the point plate). Upper LH in this picture. 

We usually shorten the slot to limit the total advance added by the centrifugal mechanism - and as Charlie says, control the speed it comes in by changing the springs.

 
 Steve Metzger       Tucson, Arizona

This diagram shows the way I stop the travel at 13° - its then 26° at the crank. With 10° initial this makes a total of 36° - a good total value for a Y-block. The full slot shown on a standard upper rotor is good for about 20° - therefore 40° at the crank, which is way too much if you experiment with elevated initial values or really light springs. Could be previous owner used light springs and a very small (or TDC) initial. 

 
 Steve Metzger       Tucson, Arizona

OK, I've solved one issue. Demons have 3 vacuum sources at the baseplate. One large, at the back, is direct, and I use that for PCV.

Then there are two ports, side by side, along the baseplate on the passenger side. I ASSumed that since they're less than an inch apart and both brass fittings resemble each other that they were both ported, that is, above the butterflies. But they're coming from different sources. One is direct, while the other is ported.

When I didn't require vacuum to the distributor, I had one capped off, and the other hooked to the vacuum pump. So now, can I hook the vacuum pump up to the direct port? My Ford shop manual doesn't specify.