56Roger, thanks for those links.  I am planning to make that conversion now, but before I do I think I will tinker with the load-o a bit.  Today I fabricated a new diaphragm for the vacuum advance can using butyl rubber flashing tape.  Even that made a noticeable improvement in pep, though not what I'd call dramatic.  

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

Stock cam, but 113 heads, tubular pushrods, high-ratio rockers & '57 ex. manifolds (glasspacks).  Also, repro aircleaner with airflow enhancement and K&N element helps. 
100K miles on the bearings/rings likely makes for quite a low-friction motor.

6 VOLTS/POS. GRD. NW INDIANA

Kahuna, if you already have an edelbrock carburetor and do not have a stock carburetor (presumably teapot) it will definitely be best to swap to the dual advance distributor. You will have to have a carb designed for loadomatic to get that distributor to work.

Daniel, thanks for that info! Here's where I reveal that the loadomatic I'm working with is on a 223 six rather than a Y, but I figure the basic info is the same. It's an automatic car and all original, so the loado has only 1 spring and post. The vacuum can is the style that can be disassembled, and it contains a mechanical stop which can be shimmed and a return spring which can also be shimmed. I believe the idea is that the diaphragm movement is controlled by the single spring up to the point of contact with the stop, at which point the return spring comes into play, which gives a 2-stage advance curve like we normally see with the 2-spring setup. I can adjust the rate of early rapid advance with the spring, the extent of it with the stop shims, then the rate of additional advance with the return spring and shims. Maximum total advance is limited by the pin slot in the breaker plate.

So a dual advance distributor may be easier to set up but there isn't one made for the 223, thus the quest for optimization

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

Also, Daniel, is your engine stock or modified? As in cam change or other?
Thanks
jim

I'm also trying to optimize the Loadamatic on my 292, as the engine is going to be stock.
My good friend Larry has the machine with the Manometer. I just want to be sure it's setup as original.
The car, when I got it, had an Edelbrock carb and the Loadamatic distributor, but the vacuum line
was hooked directly to manifold vacuum. Car ran like crap.

Good to hear from Daniel who has good info on these distributors, he would know you can adjust the spring rate by rotateing the mounting posts.


  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

I have collected a lot of info from old speed/car magazines, so was able to find an appropriate/suggested curve to copy. Drove around with a simple T'd-in vacuum gauge to get a rough idea of what happens on the road, but not much help as the signal is so weak (my ultra-accurate Sun machine-mounted manometer is really not mobile). I DID buy some other Sun instruments that should make better road tuning possible, but just never got around to dealing with it all.
You can play with the eccentrics and juggle various spring types to get really precise, but the important factor is a mechanical stop device of some kind, since weakening the springs will always lead to excessive advance & likely engine damage/pinging. I think the 50s part I converted was initially sold by Edelbrock. It had it's own adjustable main spring, and was designed to allow total removal of both Load-O-Matic springs, and it screwed into where the vac. line plumbs in. I think the OEM dual springs allow better curve flexibility, so I just removed the big aftermarket spring, and once the proper limit position was found I glued it in place, connected it to the vac. line, and sealed it air-tight with silicon.
In retrospect, it was a lot of damn trouble to go to just to prove a point, and I likely would (like everyone else does) now just recommend getting a later centrifugal distributor pre-curved by a pro shop and get on with driving. 50s era dual-point kits usually need custom fitting, aftermarket Load-O-Matic parts are now nearly impossible to find (just like good working Sun machines & people who know how to use, maintain & calibrate them).

6 VOLTS/POS. GRD. NW INDIANA

Daniel, I'm glad to hear that at least someone has been able to tune some more responsiveness into a Loadomatic.  With the Sun machine you can know exactly how you have set the curve based on vacuum input, but how did you determine what the curve should look like?  Did you drive extensively with a vacuum gauge T-ed into the carb-to-distributor line to determine what the vacuum signal actually was under various circumstances?

In the absence of a Sun machine, my thinking has been to try reducing spring load, either by turning the eccentrics or swapping in a lighter spring, to give more advance per unit vacuum applied, and road testing to see whether performance improves and whether there is any pinging.  I'm not trying to build a hot rod, just want the most I can get from what I have (stock).

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

It can be done, but takes a Sun distributor machine and some specialized hardware (plus yankee ingenuity).  I have a dual point kit in my original 6V Load-O-Matic and an extremely responsive, hot-rodded Pony teapot.  I converted an adjustable aftermarket advance stop device from the 50s to limit advance after adjusting the springs to bring advance in quicker (imitating the more desirable centrifugal performance curve).  My sun machine also has a very accurate manometer, needed since the teapot vacuum signal is so weak.  While I WOULD likely install a Mallory tack-drive if I ever get an aluminum manifold & newer carb., for now I have never felt the need since I am quite happy with the cars performance. 

6 VOLTS/POS. GRD. NW INDIANA

I believe a lack of reliable "operating information" is what defeats the Load-O-Matic advance system. The operating scheme is to monitor engine speed by means of venturi vacuum - basically sampling the "air speed" at the carburetor throat. While the reaction of the distributor to this venturi vacuum signal can be optimized - the orifices, passageways, and so on don't stay in good condition for long periods. As that vacuum system declines in efficiency (is less effective at predicting rpm)  - the engine spark gets steadily more retarded. Tends to heat the engine up - and lack in performance.

While the system can - in good condition - predict engine rpm, it is not sensitive to load. At a given rpm, air flow through the venturi is one thing - but manifold vacuum is another...... Ford changed the system near the end of its use (on the V8's) to have a second vacuum diaphragm piggybacked on the venturi set-up - the second diaphragm monitoring manifold vacuum. In practice, it tends to be a fixed offset - adding advance when the manifold vacuum is high - and subtracting it when the vacuum is low. In that manner the second pot tends to be somewhat like the vacuum pot on the post '57 systems - detects high engine load - and reduces the spark advance.  

 
 Steve Metzger       Tucson, Arizona