Vacuum advance issues - 67 200ci w/ autolite 1100

In my quest to tackle poor mileage (about 13 to 15mpg) and weak acceleration, I've upgraded a host of components from pertronix to flame thrower coil to a new (professionally rebuilt) autolite carburetor itself. Still no noticeable improvement.

Timing is set as recommended at 12 dbtdc (as per C4 auto trans specs) and I just happened to hit the throttle with the timing light still pointed at it and it's only advancing 4 or 5 degrees more. Is this all the advance it is supposed to have with a load a matic distributor? I've read from others online that their advance goes WAY farther than that, making me wonder if that's where my problem has been all along.

My vacuum advance unit is brand new and I can hold a vacuum to it without any leakdown. The vacuum from the advance port on the carb shows zero at idle (as it is supposed to) and up to 5 inches at open throttle....does that seem too low? When tuning the carb with the gauge hooked up to the port on the intake below the carb, I get a steady 20 in of vacuum at idle.

The only other thing I can think of is maybe an issue with the distributor plate and/or springs (maybe they're installed wrong?....see pic below). If I suck on the carb end of the advance vacuum line, the distributor plate appears to move freely and quite a bit more than what I would estimate 4 or 5 degrees would be.

Any ideas what could be wrong here? Is there just not enough vacuum coming from the carb to get the right amount of advance and if so is there any remedy for this?

Going off a '64 FSM available on the web...
http://falconfaq.dyndns.org/display1.ph ... Page=9-030

...and using the 'stock' table in the bottom right hand corner of that page spec would be:
"200 Six w/Automatic Transmission" (for a '64 of course)
dist.rpm.....Adv*..........hg
800..........0-1.............0.8
1200.....3.25-4.25.........1.9
1600.....5.25-6.25.........3.0
2000.....6.25-7.5..........3.8

Keep in mind those are 'distributor rpms'....so you'll double the numbers in the first and second column at 'x' level of hg. EG @1600 'crank' rpms the engine should see ~2* advance with ~0.8hg vacuum signal. at dizzy. So no, I think 5hg max, vacuum signal from the SCV port would be about right, but total advance should be [Initial + 12.5*-15*]...if my math is correct.

Could something be restricting the breaker plate from traveling its full range? Just noticing in your pic, there almost looks to be a 'brighter' piece of metal or something under the breaker plate between the two posts : Or is that an optical illusion...
Something could get lodged under there and restrict the plate movement or mechanical wear or failure of the breaker plate could also be a cause. Load-o might need a rebuild or repair, and have you done any plug reads to obtain a 'guesstimate' of A/F?

You might jury-rig a vac pump hookup to the canister or remove the canister and rig a mechanical linkage to the breaker plate, while working the the rpms up the range and using a 'dial back' timing light to see if you can introduce more advance at higher rpms....you'll probably need more than two hands for that Good luck

I don't do loadomatics, so here's a couple of links:
viewtopic.php?t=15522

http://classicinlines.com/Loadomatic.asp

I'd suggest you upgrade to a DS2 system.

Hmm okay so it looks then like I am getting enough of a vacuum from the carb but for some reason it's just not doing its job. The breaker plate seems to spin freely, but I then I don't really know what the difference between a functional/broken one should feel like. That bright piece of metal under the plate is the arm from the new vacuum advance (hence why it looks cleaner than the rest of the distributor). Can't seem to figure out what's wrong.

I suppose a rebuild is in order, but from the links you guys posted, even in top shape it's not going to be as efficient as a new Duraspark setup so I think that's what I'll do. I have a Flame Thrower coil so I'm already 1/3 of the way there.

Thanks again, much appreciated.

EDIT: Checked my '66 FSM and max vac can range from 8.25 to 12.74 dizzy/rpm (so 16.5 to 25.5) crank/rpm degrees. The adjustment is made by moving the spring posts that are mounted on 'eccentrics' (note one of your springs' posts seems to be at its zenith.

ksands18":2blimd8p said:

That bright piece of metal under the plate is the arm from the new vacuum advance (hence why it looks cleaner than the rest of the distributor).

Click to expand...

Ah, I see that now...does look like the retaining clip for the arm is missing : (maybe just removed in your pic)...don't know if that could cause binding.

I'd also make sure you have the correct vac can...'66 and ealier (shallow can ergo shallow bladder) looked like this (and according to this particular link) so did the '67...but parts references for period correctness have to be taken with a 'grain of salt' ...
http://www.championmustang.com/images/E ... /DD-12.jpg

One thing to keep in mind is your Load-o dizzy and SCV carb are a matched pair :deadhorse:
Intended to run together. You can plug the SCV port on the carb and source vacuum from the manifold. This would be okay with a '68 dizzy that used manifold vac source with the "IMCO" setup, but believe most Duraspark's used ported vac. I'm one of 'those' that thinks there is a difference so YMMV. I'd differ with a couple points in the CI article (mainly pertronix can make a diff), and keep in mind the load-o 'can' be an 'efficient' system when optimized and running correctly, but would never be confuse with a 'performance' ignition...but then I'm running an SCV carb w/full mechanical dizzy :roll: So there's always room for 'artistic license' Good luck

I adjusted both eccentrics so that the springs are forced to stretch as little as possible. I now am getting roughly 10 degrees of advance, which is 2X what I was seeing before, so definitely an improvement there.

Is there any danger in running both springs as short as possible as long as there's no pinging?

I am also kind of curious what each spring does.....is one of them used to primarily control low-end advance and the other for higher RPM's? 95% of my driving is on country roads 45 to 55 MPH.....is it correct to assume there is an "ideal" spring setting for different driving conditions that I should be worried about achieving?

EDIT: Yes, 'ideal' setting for the springs [and overall operation of the distriubtor] will produce a curve best suited to the operation of the engine given driving conditions. Adjusting springs to their weakest position likely risks excessive advance under 'loaded' conditions where advance is not wanted. The spring closest to the vac canister is for high vacuum operation, and the other is for low vacuum conditions. You can adjust the posts and measure advance in different portions of the range with a dial back timing light, but it's likely a poor substitute for proper dizzy tuning equipment and technique. A number of other things can also effect proper operation and advance signal on the load-o including; properly working scv, correct vac canister w/o leaks, bushing wear and 'free' operation of breaker plate, shaft play, etc. AFAIK they differ most in tuning technique because the typical dizzy machine doesn't apply as 'all' advance is vacuum sourced.

A big thanks for helping me understand this all....other than the Pertronix conversion, this is the first time I've explored the internal mechanics of how the distributor does its job.

I'm running both springs with the least amount of tension. The "low vacuum" spring was already there before I changed the other. This now gives me 10 degrees of advance for a total of 25 with an initial idle setting of 15. Still not pinging even under high load (accelerating up hill). I do see a slight boost in acceleration but not enough miles yet to tell if MPG went up. I can set initial advance even higher, still without getting any pinging under load, but starting it above 15 degrees gets progressively more difficult.

I'm thinking at this point any further improvement will require a distributor rebuild or replacement. If it turns out I am still only getting 200 miles out of a full tank I'll probably opt for the Duraspark upgrade or at least something newer with the mechanical/vacuum advance combo.

I have no proof other than the rebuilt units I have bought, but I think the mass produced rebuilt distributors probably set up with a very conservative advance curve to prevent too much advance which could result in claims of damaged engines.
My car got poor fuel economy but it had several contributing factors, mismatched carb and load-a-matic, slipped balancer, leaking vac advance. I don't recall the order of all those items. Anyway, have you checked that the balancer has not slipped and the indicated TDC is truly at TDC? Basically, it won't matter if you get the right amount of advance etc, if it is not occurring at the proper time.
Doug