FARMALL 460 Stalling Issue

RJG

New User
I just picked up a used (4500 hrs.) FARMALL 460 a few months ago and have been working my way through a lot of worn parts and various troubles. I thought I'd come to the end of my problems with it last week. But it still has an issue and I'm stumped.

Here's what it does. Starts up fine, choke pulled partially out until it warms up. Then it will run with the choke off. But if you gun the throttle, or put any load on the engine, it will immediately stop running. It will start right up again, but will stall as soon as you put load on it or gun the throttle. If you pull the choke partially out, you can keep it running, but it looks like it's running too rich.

Here's a list of what I've done to it.....

Replaced Ignition rotor, points, condenser, cap, wires, plugs. Subbed another coil just to rule that out. It seems to have a real good spark all the time. I've rebuilt the carburator and soaked and cleaned it, although it looked pretty good before I cleaned it. Gas tank looks good inside, and there's plenty of gas flowing to the carb. Carburetor screen is clean. I can see/hear the difference when I adjust the Idle adjustment screw and it's presently set to the sweet spot. I adjusted the ignition timing to 30 degrees Advance. The manifold heat flap and spring seem to be working very well, they're very loose and move as the manifold heats up. I removed the manifold and had it machined flat to make a good seal against the head and new manifold gasket. I checked the compression, and although not great...not terrible either. Pistons 1 & 2 are about 150, 3 & 4 are about 130, and 5 & 6 are about 150. Must be a small leak between 3 & 4, but I don't think that would cause this issue with the engine stalling under load.

I'm thinking that although is seems like two different scenarios that cause the stall out, maybe it's not. When the tractor is put under load the governor steps in and kicks up the throttle, just like when I gun the throttle by hand. This almost smells like a carburator issue to me, but the carburetor on this tractor is so simple, it's hard to believe there could be anything wrong with it. I ran wires and air through every passageway that I could find after I soaked it in Gum Out.

I'm just not sure where to look next......?

What do you all think??
Thanks.
Bob
 
Where is the main jet screw set, max power is 5 turns out. There is no "sweet spot" for the main jet.
 
Lean at the carb. Getting the passages clean is difficult. Don't take it as a flame, it just will take another cleaning. The high speed circuit is just not clean. Float level (if 1/8" low) is also a lean causing issue, but idle circuits will also act up. Jim
 
Most 460's did the samething, the carb fuel must be turned out 5 turn's to start with, or they will run like that.
 

Hi;
Yes...the main jet is set at 5 turns out. I was referring to the Idle mixture jet having a sweet spot.
Thanks.
 
(quoted from post at 18:23:20 01/21/13) Lean at the carb. Getting the passages clean is difficult. Don't take it as a flame, it just will take another cleaning. The high speed circuit is just not clean. Float level (if 1/8" low) is also a lean causing issue, but idle circuits will also act up. Jim

Hi Jim;

I hear you, but what do I need to do to get the high speed circuit clean? This will be the third time I've had it off and "cleaned" it. Some of the passage ways are completely untouchable. I used wire to feel and poke my way in and out of them. And then used high pressure air to blow into the various passage ways. What are the float specs for that carb? My rebuild kit didn't specify and I basically just set the float to be parallel with the upper carb. body.
Thanks.
Bob
 
Carb is likely fine as is. The problem is the heat
riser (flap) in the manifold. If the spiral spring
on outside of manifold is missing or broke, replace
it and the 460 will be fixed, good for another 55
years.
 
With it disassembled, soak it for at least 24 hours. Move it around in the soak at least 3 times. Then use fine wire to poke through with some spray to help juice it up. Then blow it out.
Make sure the holes in the stem of the main jet are very clean. The load jet (five turn needle) can be adjusted more than 5 turns, but should not need it.
I do not have a float height # for that unit. Jim
 
(quoted from post at 18:37:36 01/21/13) Carb is likely fine as is. The problem is the heat
riser (flap) in the manifold. If the spiral spring
on outside of manifold is missing or broke, replace
it and the 460 will be fixed, good for another 55
years.

Hi;
Thanks for the info., but I did check the heat riser flap and spring. They're both present and seem to be working well. The weight starts out vertical when the manifold is cold, and slowly moves to horizontal as the manifold heats up. It moves very easily and the spring always returns the weight to the vertical position when the engine is off and cold.
Bob
 
(quoted from post at 18:45:59 01/21/13) With it disassembled, soak it for at least 24 hours. Move it around in the soak at least 3 times. Then use fine wire to poke through with some spray to help juice it up. Then blow it out.
Make sure the holes in the stem of the main jet are very clean. The load jet (five turn needle) can be adjusted more than 5 turns, but should not need it.
I do not have a float height # for that unit. Jim

Thanks Jim.....
Bob
 
I know, but a lot of people say to adjust the main jet of that carb the same as the H and M.
 
(quoted from post at 18:49:40 01/21/13) I know, but a lot of people say to adjust the main jet of that carb the same as the H and M.
You're talking to a relative "newbie" here. How is the main jet set on the H and the M? I've set this one to 5 full turns out.
Thanks..
Bob
 
In until rough, out until smooth plus a quarter or half turn if needed under load. The carb was changed to 5 turns out with the Super H and Super M. It can be turned in for lighter loads, probably no less than 3.5-4 turns out.
 
Back the timing back down and set it at max gov. RPM for full advance . Now with out going out to the truck and getting my books out i can not tell you off the top of my head to the exact total degrees it is set at. Next set the main fuel screw to 4 1/2 turns off the seat as a starting point . And like others have said make sure your heat riser is working . Even IF the flapper is working more then likely the area around the intake tube has carbon build up and it is not allowing the exhaust heat to warm the intake properly .
 
1 5/16ths' Just finished up one . And it took three weeks to get the green slime out of it . Been seeing more of this GREEN SLIME in the past two years and it does not want to come out . Even with my KICK AH POO joy juice it is hard to KILL as that is the only words i can use as it has a tendency to come back .
 
Speaking of venturi's, last year, friend of mine called me over as he had the carb off a half dozen time and called me a few times. Tractor ran like a dream at idle, needed almost full choke to run wound up. I pulled carb and he had the venturi in upside down. Not many carbs you can do that on, I believe it is the marvel schebler. Can't put it in wrong on a 460 but could leave it out. Main nozzle can be left out also or damaged.
 
(quoted from post at 19:51:45 01/21/13) Was there a venturi in the carb & did you get it back in?

There is a venturi and yes it was cleaned and put back in............
 
(quoted from post at 19:57:33 01/21/13) Back the timing back down and set it at max gov. RPM for full advance . Now with out going out to the truck and getting my books out i can not tell you off the top of my head to the exact total degrees it is set at. Next set the main fuel screw to 4 1/2 turns off the seat as a starting point . And like others have said make sure your heat riser is working . Even IF the flapper is working more then likely the area around the intake tube has carbon build up and it is not allowing the exhaust heat to warm the intake properly .

So what you're saying is to set the tractor at an idle speed, and advance the spark (by turning the distributor) for max. RPM, and then set to the Factory specifications, which is 30 degrees advanced. Set the main fuel screw to 4 1/2 turns.

I have a question about the heat riser situation...... Let's assume it isn't working at all and it's stuck open. Once the engine is warmed up enough in a few minutes the flap is open anyway, so it wouldn't matter if the flat were stuck open would it?

It looks like my exhaust manifold was replaced not that long ago, and I believe the flap and spring were replaced at that time. It seems to be able to travel as far as it can till the counterweight hits the stop.

Thanks.
Bob
 
(quoted from post at 20:03:05 01/21/13) 1 5/16ths' Just finished up one . And it took three weeks to get the green slime out of it . Been seeing more of this GREEN SLIME in the past two years and it does not want to come out . Even with my KICK AH POO joy juice it is hard to KILL as that is the only words i can use as it has a tendency to come back .

Is 1 5/16 the float setting? That would be the distance from the bottom of the float to the carburetor surface above it, correct??

Thanks.
Bob
 
What Vet is say is to set the timing at 30 degrees advance with engine running at full throttle, about 1980 rpm, but at least 1800 rpm. Often referred to as high idle speed in service manuals. If dist is in good shape then the timing will be very close to top dead center at low idle speed of about 450 rpm.
 
(quoted from post at 21:01:07 01/21/13) Speaking of venturi's, last year, friend of mine called me over as he had the carb off a half dozen time and called me a few times. Tractor ran like a dream at idle, needed almost full choke to run wound up. I pulled carb and he had the venturi in upside down. Not many carbs you can do that on, I believe it is the marvel schebler. Can't put it in wrong on a 460 but could leave it out. Main nozzle can be left out also or damaged.

The venturi on this one only goes in one way, and I sure would have noticed if I'd left that big sucker out. The main nozzle looks pretty good on it.

I'm a pretty fussy guy when it comes to taking thinks apart and reassembling. I keep a real clean work area so I can see what came out and what has to go back in. I'd sure be upset if I finished working on a carburetor and had parts left over.
 
(quoted from post at 22:05:54 01/21/13) What Vet is say is to set the timing at 30 degrees advance with engine running at full throttle, about 1980 rpm, but at least 1800 rpm. Often referred to as high idle speed in service manuals. If dist is in good shape then the timing will be very close to top dead center at low idle speed of about 450 rpm.

Hi Pete;
Thanks for clarifying that for me. In other words if I set the timing to top dead center at the low idle speed, which I can do by turning the Distributor for max RPM on the engine, then if all else is good, at the high idle speed of 1800 to 1980rpm I should see about a 30 degree advance on the timing.

This is very different from timing a conventional car engine.
Bob
 
Not really. The critical timing of any engine is the rpm the engine will be running when it is developing full power. So, forget about timing to where it runs best at low idle as that could get you in big trouble when it is under a load with detonation or just lack of power. Put your timing light on it, mark the pulley so you can see the 30 degree mark and top dead center mark. Now, wind that engine up and adjust the timing by turning distributor until the mark is lined up with that 30 degree mark. Then, idle the engine down, take a look and it should be timed close to top dead center, if the distributor is working properly. If it is not, you should repair dist but if is is close, just forget about it. A car is no different, except auto mfgs rarely give you good marks and higher rpm test points so most just time them at low idle. Modern autos are totally different because that computer is reading several inputs for speed, load, detonation etc and the computer then adjusting timing as it is programed to do.
I will also add that most any engine will idle better with slightly advanced timing but then the loaded timing will be wrong and starting will be more difficult. The 30 degree advance is for a factory 460 gasoline engine and if that engine has been modified is not necessarily the correct setting, but I assume it is still stock.
 
(quoted from post at 11:27:18 01/22/13) Not really. The critical timing of any engine is the rpm the engine will be running when it is developing full power. So, forget about timing to where it runs best at low idle as that could get you in big trouble when it is under a load with detonation or just lack of power. Put your timing light on it, mark the pulley so you can see the 30 degree mark and top dead center mark. Now, wind that engine up and adjust the timing by turning distributor until the mark is lined up with that 30 degree mark. Then, idle the engine down, take a look and it should be timed close to top dead center, if the distributor is working properly. If it is not, you should repair dist but if is is close, just forget about it. A car is no different, except auto mfgs rarely give you good marks and higher rpm test points so most just time them at low idle. Modern autos are totally different because that computer is reading several inputs for speed, load, detonation etc and the computer then adjusting timing as it is programed to do.
I will also add that most any engine will idle better with slightly advanced timing but then the loaded timing will be wrong and starting will be more difficult. The 30 degree advance is for a factory 460 gasoline engine and if that engine has been modified is not necessarily the correct setting, but I assume it is still stock.

Hi Pete and thanks for the education.

I set the timing for 30 degree advanced at 1900 RPM and then checked it back down at Idle speed of 450 RPM and it was real close to TDC. I think all of that is OK. And yes...this tractor is stock as far as I can tell.

If I gun the throttle it immediately dies, if I slowly bring it up, it doesn't seem to have a problem. But if I put load on it at the higher RPM is will die, but I'm assuming that's because the governor is stepping in and basically gunning the throttle. I think it's still pointing back at the carburetor.....

Bob
 
ive soaked carbs in good cleaners, that tiny brass stem in the carb bowl had a bunch of debris at the bottom of the passage. had to use a drill bit n lightly run it thru there with that small stem removed. pulled out alot of debris n really helped my old 460.
 
(quoted from post at 11:22:00 01/22/13) You would need to split the exhaust and intake manifolds to check that flapper correct?

Yes...you would need to separate them. I had the exhaust and intake manifolds off of the tractor to have them machined flat. The connection point where the intake and exhaust manifolds are attached to each other appeared to be well bonded by rust, and the bolts to dismatle it were beyond fucntional. I was able to poke a very stiff wire into the manifold and feel the flap moving back and forth. Although not as definitive a method as opening it up, it seemed pretty convincing to me that the flap was still in there and opening and closing. I opted for the "feeler" method instead of trying to split the two manifolds apart and felt comfortable with the results. Bob
 
(quoted from post at 11:47:13 01/22/13) ive soaked carbs in good cleaners, that tiny brass stem in the carb bowl had a bunch of debris at the bottom of the passage. had to use a drill bit n lightly run it thru there with that small stem removed. pulled out alot of debris n really helped my old 460.

Are you referring to the small stem that the main adjusting screw at the bottom of the carb. pokes into? If so...it sits all the way at the bottom of the carb well and looks like it would be pretty tough to get out. How did you remove it? Is it pressed in there? Screwed in?
Thanks.
Bob
 
no, thats the main jet. this stem sits in the bowl gasket surface of the carb bowl,sits right in front of the venturi hole,, sticks up,, n remove it with a small std screwdriver. this is a deep internal port that can have alot of crud hidden thatll cause some problems in tuning. find ya a numbered drill bit that fits in, once that stem is removed n see if theres any debris inside. a side note, plug gap, and indexing the plugs helps run better in cold weather. ive taken spark plugs out then hooked up to the coil wire n then looked at the spark at the plug. adjust gap till you get a good hot spark.
 
Oh the fun of a 460 gas. Can't tell you a lot more from here but they can be a bugger. IH came with a zenith carburetor with a vacuum operated accelerator pump to over come the stumble on that tractor. Yours sounds like way over board though. If a quick pull on the choke while you gun it will get you up to speed I would say it is in the manifold heat riser. Like Vet already pointed out that stove inside gets full of carbon and then hot exhaust cannot circulate around the stove. Temporally tie the heat riser to the straight up position and see if that helps. If so, you need a new spring. To clean out the manifold you have to split it, those four bolts. There was some changes made in the carburetors, from double to single venturi which includes a different jet or two. Some times venturi's get changed but not the jets. Really hard to tell from here. I have drilled a quite a few main jets out for the ethanol fuel but that is a touchy job as you only go a few thousands of an inch at a time. Need it on a dyno or constant stationary load to do those kind of things.
 
(quoted from post at 17:26:34 01/22/13) Oh the fun of a 460 gas. Can't tell you a lot more from here but they can be a bugger. IH came with a zenith carburetor with a vacuum operated accelerator pump to over come the stumble on that tractor. Yours sounds like way over board though. If a quick pull on the choke while you gun it will get you up to speed I would say it is in the manifold heat riser. Like Vet already pointed out that stove inside gets full of carbon and then hot exhaust cannot circulate around the stove. Temporally tie the heat riser to the straight up position and see if that helps. If so, you need a new spring. To clean out the manifold you have to split it, those four bolts. There was some changes made in the carburetors, from double to single venturi which includes a different jet or two. Some times venturi's get changed but not the jets. Really hard to tell from here. I have drilled a quite a few main jets out for the ethanol fuel but that is a touchy job as you only go a few thousands of an inch at a time. Need it on a dyno or constant stationary load to do those kind of things.

A quick pull on the choke will get the engine up to speed, but put load on the engine and it will very quickly die.

A question about the heat riser.....once the engine is warmed up I'd assume it's supposed to be in the fully open position, so shouldn't the engine run properly at that point even if the riser was missing? It would just take a little longer for the intake manifold to get warm. Or is the flap doing something to direct the heat flow even when it's in the fully open position? Is the riser only there to help things along until it's all nice and toasty warm? Then the spring slowly pulls it back out of the way and everything is supposed to work fine?

My carburetor is the single venturi variety with no accelerator pump.

Thanks for the input...
Bob
 
should have the IH carb on it. i think the main jet size is around .055. pop that bowl off n go to the harware n find numbered drill bits. find the bit that fits the main jet as the starting point, then go up 3 sizes bigger. I would say that a .080 main jet would help the stumble n power loss if nothing else is wrong. my old 460 with a 263, the carb jetting was .090 on the main jet size, but i had her running 2300rpm. ran great! another way would be to find a 715 combine carburator that has extra ports to deliver fuel better.
 
(quoted from post at 07:01:59 01/23/13) should have the IH carb on it. i think the main jet size is around .055. pop that bowl off n go to the harware n find numbered drill bits. find the bit that fits the main jet as the starting point, then go up 3 sizes bigger. I would say that a .080 main jet would help the stumble n power loss if nothing else is wrong. my old 460 with a 263, the carb jetting was .090 on the main jet size, but i had her running 2300rpm. ran great! another way would be to find a 715 combine carburator that has extra ports to deliver fuel better.
Thanks for the suggestion ss409. Not sure I want to go there yet. I need to eliminate all other possibilities before starting to modify things. When/if I ever get this sorted out...I'll let you guys know what I found.
Bob
 
The heat riser will normally stay in heat on position, counter weight straight up and down, until very well warmed up and then and only then will it move forward if it has a good spring. In other words, like pulling a plow it will lay down. Yard work, probably stay in up right position all day long. Who knows what condition that valve inside is. May be half burned off so it is not directing heat to the stove. That is why I always take those manifolds apart when I have the head off. Flat raters won't mess with all that extra grief and work. It may have never been apart in it's life. Like I said, if you had it on a dyno and it actually worked well under load, then you could say with some certaincy carb is ok and cold puttering around work would be manifold problem. Remember, an engine never really warms up without a load. I could go on all day about those sputtering 460's. We had a customer, fairly new tractor, maybe 7 or 8 years old. He even put on a new intake manifold to over come the coughing. Then him and another customer traded tractors. Other one was diesel. They both wanted to keep their own power train so they had me do a mid section, cross switch. So, fuel tanks etc stayed with original tractor. When the guy who had the diesel came in and picked up the gas to take it home, we were on lunch break. He starts it and proceeds to take off, cough, cough, kills it, we just laughed. Welcome to a 460 gas.
 

Just an update on things with the 460. I had the carb off one more time. This time I cleaned it and ran a wire through all of the passages, and I visually inspected everthing and there are definitely NO blockages in there. I set the float level to 1 5/16" (it was just about there anyway), and set the main jet to 5 turns out. I also drained the gas tank, removed the sediment bowl and gas line. The sediment bowl and filter screen in the top of it were very clean. The screen that goes into the carb. was spotless. I purchased and put in premium grade gasoline (93 Octaine I think) and I put an extra turn on the manifold heater spring. I couldn't think of anything else to do, so I turned on the gas and fired it up and guess what? It's exactly the same as it was before......stalls under load or if you gun the throttle. I did notice with the manifold heater flap staying closed a lot longer, that when I gun the throttle (by pulling the choke partially out) the external counterbalance weight moves as if exhaust gases are pushing on it from the inside. I think that would indicate the flap is definitely still there.

My conclusion is.....there has to be something wrong with the carb. I don't see any signs of modifications or alterations inside of it, but who knows what might have been done to it or swapped out of it over the years. I'm going to replace it with another carburetor. That way I'll know for sure. I don't see any other options right now.

I'll let you all know how it turns out....good or bad.

Thanks for all of the suggestions and advice.
Bob
 

Wanted to give you all an udate on my 460's condition. Finally figured out what the issue was with my stalling tractor and it was indeed the carburator. As it turns out somewhere in this tractors past someone decided to modifiy and improve the carburator design. They removed the smaller inner section of the venturi. I didn't see or notice it because they apparently went to great lengths to file and polish the inside wall of the venturi passage way smooth, leaving no trace of the removed center section.
Sure had me fooled......but now with the new venturi installed it works like a champ....almost.

Another question for all of you experts. The governor isn't working correctly. If I gun the throttle, the motor doesn't stall....it keeps varying the speed up and down, and up and down, for quite a while. I've had the governor off and cleaned it up. There's not much to it. The bearings look pretty good, and there's not a lot of slop in any of the moving internal parts. It appears that everything inside is moving freely and doing what it's supposed to do.

I'm wondering if the external spring could be the culprit? It looks good and doesn't seem to be fatigued, but I've ordered one to replace it just in case.

What do you all think about the governor?

Thanks.
Bob
 

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