Passing Time

I'll test the mechanical advance and post back.

The vacume advance tube is the original metal tube threaded into the front passenger side of the autolite 2100 body.

Haywired

Things are sounding like its getting close. Put your vacuum gauge on the port on the carb, and if there is any reading at idle that is not the right port.
I suspect your flat spot is from to much vacuumadvance to quick causing the engine to lose power. Just my .02 cents though

Good luck

Passing Time

With vacume advance removed/plugged, mechanical advance advances to 20-25 smoothly then is a little jittery when maxed out around 30-32.
In fact total timing mark is jittery with or without vacume advance.

I'm almost positive that the vacume advance is in the correct port on the autolite with the original pre-bent vacume line. It is located on right side of the carburator body toward the front.

However, I am getting get a solid 10lbs of vacume idling at 900rpm in park at the vacume advance. Ported vacume tops out at about 20-22 at higher rpm.

Questions:

Should mytiming mark be smooth when advanced beyond 25 or so?
Why am I getting 10 vacume at the advance port at 900 RPM? (port is correct )

kalli

Hiya, as you have the autolite 2100 on at the moment, mine has only one port for vacuum. the correct ported one.
Only if you are 100% sure the timing markings are ok, then do as follows:

1. initial idle at lets say 8 degrees with vacuum disconnected at vac advance side and plugged (plug the hose to carb, not the advance itself)
2. rev up to 2500. you should get 35 degrees max (prefer 32 for the moment). if not change springs in distributor (skip if it's anywhere between 30 and 38 for the moment) all this still with vac advance disconnected and plugged
3. back to idle. Hook up vacuum advance. the timing should not change (1 or 2 degrees max. most setups 0 degrees)
4. disconnect the vacuum hose again. this time at carb side. plug carb port if possible. then suck on the hose connected to vac advance (with mouth) you should see the ignition advancing. when it does, block the hose with your tongue. The vacuum should hold as well as the timing advance. this confirms good vac diaphragm

How is it running then? can you confirm all of the above?
As well please check on the choke of the carb. make sure that this thing is fully open when test driving.

Kalli

Passing Time

With vacume advance removed/plugged, idle speed 900 in park, and static timing set at 8 the mechanical springs advancesmoothly with rpm until almost 25 BTC with a max of 32 that is jittery under the light.

Also, at idle (900rpm in park) I am getting 10 pounds of vacume from the carb port that advances my timing from 8 static to 19-20 BTC when plugged onto the distributor .

total timing with all connected is 33-34 at 3000rpm.

stumbles when initially starting and requires continuous gas pumping. runs smoothly and starts instantly when warmed up.

kalli

that sounds ok from the values, but I don't get the jittery part.
It could be 2 things
a) is it an inline strobe or one with inductive clamp. If inductive clamp make sure it's the right way round and you pick up at the lead on distributor side, not plug side of lead
b) the mechanical advance is no good. Have you tried oiling them (very very slightly). is it a new distributor? or 40 years old?
c) try at engine stop to move the distributor shaft forth and back. It must not move, only turn.
When you turn it, it should snap back without hesitation

as Tad says: must be the wrong port on carb. You should have no vacuum at idle when hooked up to ported vacuum
If there's only one port (maybe take picture. if you do make sure we get to see the whole carb, not only the port), then maybe you have curb idle too much and rtegulate the idle down with the idle mixture screws?
They should be as follows (rough estimates): both idle mixture screws one and a half turns open from seating. Curb idle screw just so that it opens tyhe throttle for a tiny bit

that sounds fine with vac advance disconnected and plugged

stumbles when initially starting and requires continuous gas pumping. runs smoothly and starts instantly when warmed up.

edit: do you have breaker contacts in your distributor or do you have inductive pickup (electronic module) ?