Thanks to both TrickSix and bubba22349 for clarifying the component sharing between the '67 and prior Load-O-Matic distributors and the '68 and later centrifugal advance distributors -- much appreciated, fellas.
At this point i thought I'd share my recent experiences in attempting to replace the early L-O-M distributor in this '68 engine/carb combination my neighbor wound up with when he bought this early '64 1/2 Mustang coupe last month. Unbeknownst to him, it was not the original '64 1/2 170 six in the car, like the air cleaner decal advertised it to be. It turned out to be a '68+ vintage 200 six with a matching '68+ non-SCV style Autolite 1100 carb. So, he had a bad combination of a newer non-SCV carb and an older L-O-M distributor. So, the task was to find a proper '68+ point style distributor that would work properly with the non-SCV carb. Yes, he did not want to jump into a DSII or other electronic distributor at this time -- maybe I'll successfully talk him into one next year.
Our first stop for a replacement distributor was Rock Auto where he bought a brand new (not rebuilt) Cardone distributor, p/n 842613, spec'd for the '68+ 200 six. When it arrived, I checked the integrity of the vacuum advance canister and discovered it would not hold a slowly applied vacuum from my MityVac hand pump. It never made it into the engine, nor did I bother checking the advance limit plate to see what amount of centrifugal advance it would have allowed. So we sent it back for a replacement, without me realizing what a defective design this new Cardone piece really was.
When the 2nd Cardone #842613 arrived, the vacuum advance can checked out "good". At that point, I pulled the distributor apart and repositioned the (unmarked!) advance limiting plate to allow only a total of ~20 degrees centrifugal advance, then set the point gap at 0.025". Not being at all familiar with most any Ford products, but having a good understanding of the general function of point style distributors, I then applied vacuum to the advance can and, to my disbelief, watched the point gap shrink to nearly zero as the vacuum increased to 20"! This made no sense at all to me. Upon closer inspection, I observed that the Cardone points breaker plate pivots from a single fixed point, opposite the points, that is located part of the way out to the housing's edge. By using this very simple offset single pivot point between the breaker plate and the support plate below it, the dwell (point gap), by definition, will absolutely change with varying amounts of vacuum applied to the can. Any OEM Mopar or GM points style distributor does not act this way at all -- with them the breaker plate moves under vacuum advance in such a way that it rotates concentrically around the mainshaft centerline, and by so doing, the dwell (point gap), also by definition, will not change with varying amounts of vacuum applied to the advance can. This brand new Cardone designed/manufactured p/n 842613 distributor ignores this fundamental design practice for whatever reason (cost?). As such, the basic design of this p/n 842613 distributor is seriously flawed and makes this distributor essentially worthless. We put it into the engine anyway to see what would happen with it. Not only did the dwell vary tremendously with varying vacuum levels as I suspected it would, the car stopped running after 10 miles. At this point, we attempted to pull this distributor out of the block -- it would not lift out regardless of how hard we pulled on it. We had to resort to levering it up using ever-larger flat blade screw drivers before it finally came free and once it did, out came the oil pump intermediate shaft with it. Rechecking the point gap on the cam's nose at rest showed it had decreased from the original 0.025" down to 0.002" -- how could this happen in 10 miles with lube confirmed in place???. Again, talking with wsa111/Bill Ambler, I learned Cardone miss-machined the long mainshaft support bushing in the housing on many of their new distributors, causing the mainshaft to run at a slight angle relative to the distributor housing's centerline. By running in this fashion, the oil pump intermediate shaft bell-mouthed the hex socket in lower end of the distributor shaft, which then locked the distributor into the block -- the housing would freely rotate but the unit would not come out of the block. By levering it out, the bellmouthing was forced to collapse onto the oil pump shaft, trapping it in place in the bottom of the distributor shaft. Once all this was discovered, it got sent back to Rock Auto for a full refund, which they honored.
Our third attempt to get a functioning points style distributor was to locate a used, genuine Autolite points style/centrifugal advance unit from '68+ which I was able to find on ebay for the not unreasonable price of $49. When it arrived, the vacuum advance can integrity checked out OK. I completely disassemble this distributor, cleaned it thoroughly, thanks to some excellent advice from wsa111 -- this fellow, Bill Ambler, knows his stuff and is most helpful! I moved the advance limiting plate from the 15L to 10L position to limit it to 20 degrees max centrifugal advance. Then, when I applied vacuum to the can I (thankfully) witnessed the points breaker plate moved very nearly in the correct concentric rotation around the cam, like I had always seen on Mopar/GM points distributors. I discovered the reason the Autolite distributor breaker plate has this "proper concentric rotation" is due to the interaction of the breaker plate and the mounting plate below it -- there is some engineering plastic material attached to the lower plate, with pins protruding up into guide slots in the breaker plate that forces this type of concentric motion of the breaker plate. Why in the world Cardone thought they could get away without having this correct concentric rotation of their breaker plate is beyond my comprehension. At this point I knew we were on the right track. So, I put in fresh NAPA/Echlin points, condenser, rotor and cap and the car has been running perfectly ever since, with a stable dwell.
Moral: Do not, under any circumstance, bother to buy a Cardone p/n 842613 distributor for a Ford small six. In fact, I would be suspect of any products coming from Cardone, just based on their irrationally designed vacuum/breaker plate system they intentionally chose to employ in this newly designed and manufactured distributor of theirs. Just how good (or bad) are the rest of their products if they are willing to market poorly engineered new distributors???
