First AC may be my last

firing order should be 1-2-4-3, #1 is by rad,

'magical' 20 minute run could be overheating coil. There's lots of 'combinations' of coils, ballast resistors and batteries.

The simplest would be 12 volt battery and a 12 volt coil marked 'INTERNAL BALLAST'. This setup would require you to bypass the original ballast resistor. Two of my D-14s were originally 6 volt, so when I perverted to alternators and 12 volts I ADDED another ballast resistor to 'lose' the extra 6 volts the 12 volt battery supplies.

If the gas tank cap is kinda loose, then it's probably not a vacuum problem. Try running it ,under load in the field with the cap off.  Simple,easy test.

A-C made 2 or 3 models of SC-3PT adapters. 1 version is for implements that need power from the PTO ( say a rototiller) , the other doesn't ( like cultivators). You've got 3 options to buy 1) find original stuff online, 2) buy aftermarket versions , 3 ) make your own. Two of mine are A_C but bodged, not complete, 3rd is homemade. I LEAVE the toplink ON the adapted implement so I don't have to fight and adjust  it everytime. Now what you will need is the top link mounting bracket  for the tractor. It bolt under the seat, just longer bolts. LOTS of homemade versions , mine is a nice copy of the OEM 3 hole version.

Jay

Operator's manuals can be found cheap on e-bay - the only things I buy on that site. 

Refurbished can mean different things to different people.  It's very common for people to do a quick 30 minute paint job and call it refurbished.  As mentioned above, a cheap paint job can cover a lot of mechanical issues.  Sounds like you got sucked in - several people do.  I have learned to look under the paint and focus on the major mechanical aspects - Engine, transmission and rear end.  The issues you are dealing with are not catastrophic failures by any means.  You must also keep in mind that these tractors are over 50 years old and you probably do not know its maintenance history.  Once you have things ironed out, It should be a good and reliable machine for you.

Whenever I get a new tractor, I do a thorough maintenance so I know I will not have any problems when I put it to work.  Clean fuel tank, sediment bowl, carb, rad flush, thermostat, battery cable and wiring inspection, coil, distributor cap, wires, plugs, rotor, electronic ignition conversion, new filters and all new fluids.  Some of these may not be necessary, but I know what I have done and they should be good. 

This forum does have a great deal of knowledge and experience here, but you also have to be able provide as much detail with your issues and what you have done to try and solve them.

Welcome to the group!

First off... it kinda sounds like there's a whole lotta useful history that you don't have, and that makes things difficult to understand, I'll toss in a few things that others have already made some reference to:

Positive ground IS A STANDARD... as is six-volt.  Negative ground is 'modern' standard, as is twelve-volt.

The Ford you're familiar with has a Ferguson-System three-point hitch.  Harry Ferguson invented it... and Ford PARTNERED with Harry, to get EXCLUSIVE use of his PATENT.  NOBODY ELSE used a three-point hitch from the time that patented system came out, until the patent expired around 1961.   Every OTHER manufacturer had their own implement coupling and lifting system, and had their own name to go with it, and some may have gotten dangerously close... NONE of them infringed on Harry's patent.

AC's 'snap coupler' system was a standard for Allis tractors prior to 1962ish.  Case had the 'EAGLE HITCH'... IH had a system, Deere had a system, MM/Oliver/White/Cockshutt... everyone had their own.  The battleground wasn't a farmer's soil- it was the courtroom across the street from the US Patent Office.  After the Fergie patent 'matured', the 'three point' as we know it today, became a 'national standard' of sorts, albeit with more improvement, as in size category.  Just so happens my My '52 WD and '57 D17 have Category II 3-point hitches, but that's because I have a bandsaw, lathe, mill, and welder in my shop, and a Farm & Fleet on the west side of town.  They both work great with any 3-point implements I wanna hook on.  There's guys that build 3-point kits to fit your tractor, and you'll find that they yield exactly what you're looking for.

Older tractors with hydraulics had a 'different' standard as-well.  Your hydraulic system is low-volume (3gpm or so) and high pressure (excess of 3000psi).  'Modern' hydraulic systems are higher volume (5+ gpm) and lower pressure (1800-2500psi or so).

It was 'standard' back then to have hydraulics that operated DOWNSTREAM of the engine clutch... meaning... not 'live'.  This was 'standard' because a fully-live hydraulic pump can exert tremendous drag on an engine that's trying to crank to life on a cold day.  Modern tractors just accommodate that with brute force... (did I mention 12v...)

Your tractor has a distributor with contact points.  That can either be replaced with a new set of contact points, condenser, cap, wires, and plugs...   or replace the contact points and condenser with an electronic module (a Pertronix Ignitor, for example) and by doing so, eliminate the problems we experience with all the lousy imported ignition components (condensers and breaker points) that we've had for the last decade-or-so.  

The distributor cap gets dirty, and sends spark energy astray.  Spark plugs get dirty and carbon foul.  Distributor shaft wears and causes the breaker contact action to be incredibly unstable.  In many cases, there's sufficient spark energy to run nicely at idle, but when you apply a load, dynamic compression pressure rises far enough so that the ignition simply can't fire, hence, miss and bog.

Lean fuel mixtures will ignite with minimal spark energy under low dynamic pressure, but it will NOT fire once chamber pressures rise.  Carbeurator fuel float level is critical to maintain proper mixture, there's a fair chance your carb float and needle valve aren't doing so well.

There's typically a fine-mesh catch screen located in the carbeurator's fuel inlet fitting... if you have sedimentary gap in there, particularly steel sediment in ethanol... it's turning into goo and impeding flow.  Open up the drain petcock on the bottom of the fuel bowl.  it should make a big, clean puddle of gas on the ground... if it doesn't go through the fuel feed system from fuel tank onward.   if the tank is cruddy, drain it good, and clean the tank in any number of ways... my preferred method is a fist full of misc. nuts, bolts,  and washers in my parts tumbler... after they're done rolling around, the inside of the tank is usually scoured clean of loose debris... I rinse it out with a little gasoline, and clean from the top of the fuel petcock pickup tube, all the way to the carb jets.

Service manuals back then were typed by hand, then typeset with screen images, then printed on an offset press.  Press time and paper were expensive.  For the sake of realistic economics and practicality, the manual authors expected that an individual who held the manual had already sufficient life-experience with the basic recipie for internal combustion to be able to troubleshoot things like fuel, air, compression, timing, ignition... (rinse and repeat)... so they did NOT waste time or paper to rewrite what they considered 'common knowledge'.  If that's out of your current skillset, then you've come to the right place... these guys will walk you through the process, just as long as you're reasonable  and seem self-applied.

I assure you that if you were to put it alongside a modern tractor of same advertised size, that the Allis will prove itself well worthy of the tasks-at-hand, and it will last much, much longer, and cost much much less to maintain.  it DOES mean that you'll have to learn how to be the maintainer and troubleshooter.

Oh, and I know you've named it "Big Al"... but one thing you should know, is that the moniker "Big Al" refers to the Allis-Chalmers 25000-series diesel engine.  They're also referred to as the 'Purple People Eater'.  Do a Youtube search for it, and you'll see 'em in action.

By the way...

For those that work on lots of 4 cylinder engines, you may think that the Allis firing order is 'not standard'...  Many others frequently used 1-4-3-2.

When an Allis 4 cylinder (B, C, CA, WC, WD, WD45, D17) engine is running, and you have relatively close compression and valves set within reasonable range, and there's no vacuum or exhaust manifold leaks, the engine will run so even on all four cylinders, that you will NOT be able to tell which cylinder is firing.

On a 1432 firing order, that's not usually the case.  Here's why:

The intake and exhaust manifolds on four cylinder inline engines consist of one central point, which happens to be physically closer to the center two ports, than the outer two ports.  This means intake and exhaust flow to the two outer cylinders makes a longer trip, than the two closer... so the port and runner distance for the outer two cylinders has different volume, and different velocity.    Allis's design engineers understood this.  They also understood that when you fired two cylinders adjacent to eachother, that the intake and exhaust pressure pulses from one cylinder, affects the adjacent cylinder.

They also realized that when you 'share' a port (as virtually every other manufacturer did), you wind up with 'funky' airflow.

So they designed the ports, runners, and FIRING ORDER to yield really close (not perfect, but really darned close) balance between all cylinders.

Next time you're listening to an engine, listen for the weak and strong exhaust pulses, and watch the crankshaft turn.  If you watch the crankshaft sheave with your peripheral vision, you'll probably be able to 'see' the crankshaft angle 'match up' with the rythm generated by a weaker power pulse.

As for other characteristics to note... and the other guys will chime in if I'm wrong...

I believe the 'small block' B/C/CA/D10/12/14/15) fours might be susceptible to the 'big block' (WC/WD/45/D17) manifold leak and erosion issue, so look out for exhaust and intake leaks always.  Exhaust manifolds, because of basic thermal expansion, expand and contract more than the  liquid-cooled head.  Allis's casting engineers did an awesome job coming up with ways to allow for that, and maintain a seal, but seals don't last forever.  After these machines have spent five decades in the field, the head bolts start to corrode and stretch faster, and a little exhaust leaks out, typically at the farthest ends ('accumulated deflection', because it's expanding in an arc).  On a dark night, one can 'see' exhaust manifold leaks as little wisps of fire sneaking out 'tween the manifold flange and head.  This greatly affects how well a cylinder breathes, and furthermore, erodes the cast iron where that blue flame licks away the metal.  When this happens, it's necessary to either resurface or replace the manifold and put in new gaskets.  When I acquired my D17, it had been sitting for half a decade, parked due to lack of power after it'd been running a while.  After a carb/tank cleanout, I experienced power drop after putting a load on it for a few minutes.  Rebuilding distributor and going electronic ignition helped (dizzy shaft was loose in the bushing, as they do), but making a climb up the gravel road hillside to my south one night, I saw 'afterburner' flares out the #1 towards the cooling fan, and knew what was up.  After fixing that, it has run flawlessly.

BTW... you CAN convert your tractor to 12v negative ground if you so desire.  All of mine are, and I've changed mine all to alternator, rather than generator. 

The polarity sensitive issues include the battery connections, ammeter connections, ignition coil connections, and generator and regulator

Battery connections obviously need to be swapped. 

Ammeter leads, also need to be swapped (if not, charge indicates discharge, and discharge indicates charge).  If you ever wonder if someone has hooked up a battery wrong, leave ignition off, turn on the lights.  If the ammeter needle shows charge, it's backwards!

Ignition coil.  Ignition coils will 'work' when wired in either direction, but with the ignition coil's polarity being backwards, you'll get excessive pitting on the contact points, and rapid plug erosion.  Some ignition coils (typically less expensive or 'high-performance' coils) are wound such that they'll internally 'leak' to case in operation, and the coil will erode, overheat and fail.  OEM Delco coils that these tractors were built with, were built very well... as were the breaker points and condensers.  Modern 'common' replacements are all sourced through southeast Asia, and for lack of a stronger, but socially overwhelming term, they downright suck.  Don't be surprised if a tuneup kit, brand new out of box, has a flaccid point spring and totally unuseable condenser.

Generator and regulator will they will change polarity easily, but they need to be worked a bit in order to 'unlearn' positive ground and 'learn' negative ground.  In more technical terms, the polepieces of the generator and regulator develop residual magnetism accordant to the polarity with which they were previously tasked.  Changing polarity means the polepieces need to be degaussed (cleared of that magnetism) and slightly magnetized in the new polarity.  Doesn't take fancy machinery to do it, as they will do it by 'brute force' as long as you start the machine up and make the electrical system do some hard work for a while.  Or you can disconnect the regulator wires, tape them, fit an alternator to it, and be happy.  There's a myriad of options, everyone has favorites, and every alternator (ooh... brace yourself for a bad pun) has it's PLUSSES AND MINUSES! 

(sorry, I just couldn't help myself).