I certainly understand your Opinion on this Post. However as I am sure you are aware in 1957 Ford went to the "Dual Advance" Distributor which are far more responsive to Load (Vacuum advance) and Engine Speed (Centrifugal Advance)  at the same Time the Holley 4150 Carb. was added. The Combination of the 2 really woke up the Performance of the Y Block. Even upgrading only the Distributor to the dual Advance type  makes a big difference in the way these Engines perform even retaining the Teapot Carb. The recommended initial Timing Specs  using the Loadomatic were also very Conservative. There's not a lot U can do to improve the the Stock Loadomatic Distributor Characteristics.   I have converted 3 1956 Y Blocks to the 4160 Holley and 57+ Distributors. 2 of my Own and a Buddies 56 that had a rebuilt Engine installed and it ran like a Dog until I convinced Him to spend a little more and convert it to the better Setup. Nothing that can't be reversed but personally I don't see myself ever reverting to Stock Setup. I like to drive My Cars and enjoy them as well as I think improved reliability and not having to worry about under hood Fires. Just my own Opinion and I don't knock anyone who stays Stock.

  

Thank God and all you Y-Blockers, especially Tedster for yesterday's post.  I learned more today about a vacuum gauge than I have over the last 60 years of bending wrenches.  My old gauge, complete with original use instructions, led me to minor adjustments to the idle screws and to the timing.  Gauge read 18 - 20 at idle, down to 5 and up to 25 with a snap of the throttle, and back to 20 at idle.  Took it for a spin and didn't feel or hear any misses and came up the hill to the house in 2nd gear with no hiccups or hesitations.  Looks like I'm back on the road again!

There's nothing that says the engine can't be converted back to the teapot carb and LOM distributor upon resale. Still, I "get" that you want to keep it original configuration and get it running right.

Did you get a manifold vacuum measurement with a gauge yet? This is a quick and easy way to determine basic internal mechanical engine health and setup. Compression, valve adjustment and ignition timing. Run the engine at a normal idle RPM. At Sea level you're looking for a steady needle at 18" to 20", if you snap the throttle it should drop to around 5" and rebound to 25" or so before returning to 18" to 20", this means the compression is reasonably good. It doesn't replace an actual compression test, but it's pretty accurate. And saves wear and tear on battery and starter and is a lot easier. There are several charts available for download on reading a vacuum gauge, the amount of info that can be gleaned is extensive in the hands of a competent mechanic.

Thanks again for all of the information - sure wish I had a Sun Tune-up machine. . . . . .  My car is a stock 1954 Sun Valley and I suspect all of you know it is quite valuable.  Because of that, I do not want to make any modifications (except minor) that would have an impact on its value.  I know that changing out the rebuilt teapot to a more modern carb with corresponding intake and distributor would probably make a good fix.  However, as above stated,and the fact that I too am stubborn, I want to make it run like it is supposed to.  I'll check the compression today to rule out any associated internal problems and then pull the carb again for re-inspection and repair (if necessary) in the spark control and the secondary throttle vacuum assembly, both of which probably have an impact on distributor vacuum.  Please bear with me - with the combined knowledge of all you Y-Blockers, we can get this ol' beauty back at the car shows again!

I've read (some) conflicting information, claims that the LOM was actually a very fine distributor advance system when setup and operating correctly. Perhaps not for performance applications, for general use. I've also read they had excellent fuel economy.

I don't know enough about them to say my opinion, other than there are generally plenty of obsolete automotive components that work very, very well for their intended purpose when understood and adjusted correctly. It wouldn't surprise me a bit if that statement about LOM distributors were true, put it that way. Sometimes it's just the nut behind the wheel that's the problem! Usually what happens is somebody swaps out the carburetor, and the head-scratching begins.

Btw, a "ported" source of engine vacuum (above carburetor throttle plates) will not have any vacuum at idle RPM. If you start swapping hoses around with out a clear understanding that isn't going to help the issue. Odds are they were correct or only install one way? I would never install a LOM system but I'm stubborn enough if it had one I'd want to understand it and make it work as advertised. Maybe acquire a post '57 distributor and start setting that up too.

Take it one thing at a time. You have the manual, that will help a great deal.

Once upon a time my father - who was coaching my friend and I about tuning multiple side draft carbs ('67 Triumph Spitfire) - proceeded to give us a shopping list that included clear aquarium tubing. He promptly fastened it on a plywood backer in a deep "U" (dunno the details nearly 50 years later) and poured some distilled water in there. Basically created a backyard manometer, read with a tape measure. Such an approach is probably still available today if you want to try it out - there must be something on Google....  
The last time I used such a device it was called a "slack tube" and I borrowed it from a local Detroit Diesel distributor.

 
 Steve Metzger       Tucson, Arizona

Miker and Sandbird, thanks for your replies. . . .  Just came back from from NAPA with the same info on low vacuum, so I will not hook up to the manifold and will recheck my gauge to see if it reads low enough - probably not.  The teapot does have a spark control valve and I will look further at the repair manual for clues. . . . . . . . . .

Along with what Sandbird mentions, unless your vacuum guage reads real low, you might not see a reading, especially at idle and just above. It’s a very weak signal, more in the manometer range than an automotive vacuum guage.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

If you connect a loadamatic distributor to intake vacuum it will go to full advance immediately. They only need about 3 in vacuum for max advance may damage an old diaphragm if you hit it with
15 to 20 inches of vacuum. Get a hand operated vacuum pump to check your distributor advance. If you get no vacuum from the carb when you rev it a bit the carb is at fault. Not too familiar with a 54 Tpot if it has a spark control valve you can change it other than that it may have to come back apart.

Kahuna and Tedster, more diagnostics today and find that there is NO vacuum at the carb vacuum advance port, let alone at the dist.  Rather than take the teapot apart again to see if there is a blockage to that vacuum port, I will re-route the vacuum line from a manifold location using a tee block and then retest for advance.  Yikes!