I have just thought of something which I think may be the real source of the problem.

I have been studying the specs listed in my manual and in the manual for my sister's 1970 Dodge Polara with a bone-stock, original 318.  Both manufacturers call for a very similar advance curve, and one in which if you add the max advance limits at the crank of each component of total timing, you get a number in excess of 60 degrees at the crank.  When I observed the advance behavior of the Polara, though, I noticed that I was able to increase engine speed a couple hundred rpms before a vacuum signal to the vacuum advance ever occurred.

Further study of that manual showed conclusively that the vacuum advance pickup port is ABOVE the throttle plates when they are resting at idle position.

Is this supposed to be the case for the autolite 2100 as well?  Because I have a low vacuum signal even with the engine idling at 600 rpm in park.  The mixture screws are happiest 3/4 turns from lightly seated.  I am wondering whether the throttle plates might be misaligned in the throttle shafts.  I have messed with them so it is certainly possible, though I'm sure I tried to seat them properly before.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Does unhooking the vacuum advance line and slowly bringing the rpms up eliminate the ‘missing’ you’re experiencing?  If so, then hook up the line and drive the car.  You may find that the car drives just fine with the ‘missing’ you were experiencing in neutral or park now gone.  Under a load, the advance curve will react differently than checking it when speeding up the engine in a no-load situation.

Yes.  At idle, the vacuum port in the carb throat for the distributor is just above the throttle blades at idle.  That means effectively no vacuum signal to the distributor at idle.  As soon as the throttle blades are opened enough to expose that particular hole to the lower portion of the blades, a vacuum signal will be generated at that hole.

Lorena, Texas (South of Waco)

62 galxe!Kenny,I just had a look at Rockauto.com for a distributor advance for 62 Galaxie with 292.Standard # VC-31 or VC-25 are listed.These are the Allen key adjustable type.The instructions will tell you to turn the adjustment screw the same # of times as your original unit.Because yours is damaged you will have to set it from scratch as described in this post.Check your local parts supplier.They should have a listing by vehicle application if they dont sell Standard parts.

  

Ted, you are right, while driving I do not notice the missing and shaking at low engine speeds that I get in park.  With the vacuum advance disconnected in park there is no missing either.  But just because an engine isn't missing doesn't mean it's advance curve is set right, and I have taken the miss in park as a clue that some aspect of tuning (most likely advance curve) is off.

The way things are now, the vacuum pickup port in the carb throat is approximately even with the throttle blades at idle.  Looking into the carb, I can clearly see the uppermost of the two idle transition holes above the throttle blades, but I cannot see the lower transition hole nor the advance pickup port.  Yet, as is, idle speed is just 600 rpm.  I can't shut the throttle plates much more without stalling the engine.

To anyone with an autolite 2100: where are your mixture screws set?  Are both idle transition holes visible above the throttle blades, engine idling?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

This is great stuff, and Im looking at this at the moment.

Mark, can you give me the link for those springs you got .

Steve, Can you explain the orifice? can it be used to lower the vacuum?

AT this point I have set mine at [ with no vac] 13* initial , 28.5* @ 2750 RPM, 35* @ 3300RPM.

with vac 51* @ 2930RPM, 53.5 @ 3280 RPM . I have no pinging. seems I need a bit more work



"Came too close to dying to stop living now!"

The Mr.Gasket # is 925D.2 springs in the kit.You have too much total advance.You need to go through the steps suggested as far as checking which cam# is engaged on the stop.I believe you are using the 57+ distributor.Correct?Initial advance on mine is 10 BTDC,8 degrees of vacuum advance adjusted on the can and the cam set on the 13L slot which gives maximum 26 degrees centrifugal advance at crank. 10+8+26=44 maximum advance.All in under 3000 RPM.With the total advance available on yours it may not ping but at high criuse condition it will likely "surge"or miss because timing is too far advanced.

  

Its a 59 dizzy. off the top of my head a V8 normally runs a total of 36* total mechanical advance, so I should be able to run it without the vac advance ok anyway.. HAd to do that to my Cuda as MOPAR vac advance are crap.. goes ok.. Look forward to more on the topic and sorting it out.



"Came too close to dying to stop living now!"

Actually the vacuum advance is important for low end performance and fuel economy.You would only run full centrifugal in a race car OR a street vehicle with extremely radical cam.

  

Looks like I have the spacer type vac advance, so how do these adjust??

Greenbird.. CAn you give us the rundown on the orifice ...? How what and where...



"Came too close to dying to stop living now!"

The advance canister shown below (disassembled) has two items that can be adjusted.

After you unscrew the hex cover from the can -there are shims that preload the spring. Adding or removing shims changes the advance travel position versus vacuum applied. If the spring preload gets up to a point where the vacuum can no longer overcome the spring sufficiently to reach the mechanical stop - then it would also have the effect of limiting the total vacuum advance available.

The fiber tube is factory sized to limit the travel of the unit at a particular amount. By installing a longer tube for instance, the total travel would be limited. Both of these items are subject to experimentation.

To run "hard lines" on my outfit, I used brake tubing formed to fit on the manifold - roughly run like original. Its attached to the carb and the distributor with rubber tubing at both ends. At the distributor end - I inserted an electrical "butt splice" (red plastic cover) - and crimped it until the system behaved the way I wanted it to. Others have used a solid piece of brass/plastic/steel and drilled holes to get it to behave properly - try a 1/16 hole and see what that does for you. When mine was working to suit me - I pushed the rubber over the butt splice enough to make it invisible.

 
 Steve Metzger       Tucson, Arizona