Farmall H not running right

I have a 1943 H, i have given the motor new rings, rod and main bearings. I had a hole in my manifold welded with nickle rod. i have a new head which i re seated the valves in. new head gasket also. I also have a rebuilt carb on it. at max RPM, it fires beautifully with out a problem. but when i turn down my idle screw it doesnt run smooth anymore, it gets rough. also after turning the idle so low to a certain point it backfires out the carb. can anyone help me? im clueless here.... id like to get the idle slow and smooth like its supposed to be. any help will be greatly appreciated! im young and eager to learn. rebuilding this piece of history at the age of 19 is one hell of a learning experience

A high probability is a non functional centrifugal advance system. If the springs and pivots in the distributor are 65+ years old they may deserve retirement. If you are capable it is not too bad to dig into it and repair. (under the points plate) Timing the engine so it runs well at high speed but stumbles at idle is indicated. If timing it for idle smooth it will run poorly at speed. Put a timing light on it and see if it advances from idle to wide open. Jim

Jim,
i have never been inside a distributor before other than to sand the points to gain spark when i fired it up for the first time. i do not know much about this tractor other than it has sat for the past 4-5 years. i cant do anything on this tractor or the next 2 weeks which is killing me because than means two weeks of pondering. when i get to the tractor, ill get out the I&T and see if i cant get in there to see what going on. Thanks! -Shane if you can think of anything else that may be a prospect im open to it.

Let me see if I can post my carb tuning procedure here. Might help;
Make sure the float isn"t sticking or touching the insides of the float chamber. Some previous advice was to use a Dremel tool and smooth the insides of the float chamber so it doesn"t rub or touch. Pretty important. Set the float so the top of it rests 1 27/32" above the flat surface of the float chamber.
Initial settings as follows to get it started;
Main fuel adjusting screw, big screw facing down at an angle, towards the rear, at the bottom of the carb; 2 1/2 to 3 turns open. This main screw turns clock-wise for leaner mixture.
Idle fuel-mixture screw, smaller screw facing forwards, on upper left-hand side of carb; 1 to 1 1/2 turns open. This idle screw turns counter-clockwise for leaner.
Idle speed screw, faces outboard, at the top of the carb; set for 450 rpm, and make sure the governor correctly engages the slot.
Get the engine warmed up, and idling.
Turn OUT the idle fuel-mixture screw until rough running, then turn in until it idles smooth. (Mine is set at 1 turn open.)
Rev it up, wide open, warmed up, then turn the main fuel adjusting screw IN until rough, then out til smooth, then 1/4 turn to 1/2 turn further out. As I say, mine sits at 1 turn open. (Other advice has been to set it at 2 1/2 turns open for pulling implements.)
Should rev up smoothly and evenly.
Too Lean = stumble, sputter, damaged melted plugs.
Correct = tan plugs.
Too Rich = back smoke, black sooty plugs.

Don't tear into it before you shine a timing light on the pulley to see if it has the problem. At low speeds near or at 500 it should be near or a little before TDC. With greater speed it should advance into the 20 or 25 degree range (IIRC)"look up the timing specs. for best results". Jim

upon talking with my boss who patched the manifold, he believes that he did a poor job on patching it. when running fast, he says there is less vaccum. but when running at a slow idle, he believes the higher vaccum is cauing it to suck air through the poor weld job.
Also upon thought. cylendar 3 is leaking oil from the plug hole. now, the new rings have not been ran enough hours to set perfectly, but what if clyendar 3 isnt firing at the slow idle due to oil in cylendar? maybe i have a bad new champion sitting in that hole?. so many things to check when i get back to school... and so much more to lose sleep over at night :/

Put a cover of JB weld over the manifold to assure the leak stops, No heat problem on the intake side. (they can also leak between the exhaust and intake at the connecting stove area, less easy to check on the tractor.
A oily plug means the gasket might be bad or the plug wasn't tightened well. If it is missing on one cylinder, swap the plugs or change them to see if it picks up. Also setting the valve adjustment might be a good idea. Jim

(quoted from post at 18:15:21 05/10/13) I have a 1943 H, i have given the motor new rings, rod and main bearings. I had a hole in my manifold welded with nickle rod. i have a new head which i re seated the valves in. new head gasket also. I also have a rebuilt carb on it. at max RPM, it fires beautifully with out a problem. but when i turn down my idle screw it doesnt run smooth anymore, it gets rough. also after turning the idle so low to a certain point it backfires out the carb. can anyone help me? im clueless here.... id like to get the idle slow and smooth like its supposed to be. any help will be greatly appreciated! im young and eager to learn. rebuilding this piece of history at the age of 19 is one hell of a learning experience

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Just curious, but did you use NEW gaskets when you re-installed the manifold?

You should be able to find a GOOD, used manifold for your H for around $100 or less. I know $100 is quite a bit for a 19 year old, but it's something to think about.

the manifold gaskets are new out of the wrapper. the gasket from the carb to the manifold is not. i make a decent check a week... a hundered is not a problem. problem is where to find it. i work so much plus school, i have no time to run all over hell to get one. when im out of work, everything is closed

the gasket better not be bad... its a brand new one. although i didnt get the head resurfaced. also the valves have been adjusted twice. maybe a third time is in store, and i am adjusting them according to the manual. it says to adjust them hot. i adjusted them hot twice. as far as plugs, they are new from the box, properly seated as well.

(quoted from post at 17:01:29 05/12/13) the gasket better not be bad... its a brand new one. although i didnt get the head resurfaced. also the valves have been adjusted twice. maybe a third time is in store, and i am adjusting them according to the manual. it says to adjust them hot. i adjusted them hot twice. as far as plugs, they are new from the box, properly seated as well.

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I'll give you a suggestion on the valves. Set the gap at 0.020" COLD. Much easier and maybe even more accurate. The gap will be right at 0.017" when the engine is at operating temperature. Quite a few of us do it that way.

Tractor update, i got my hands on it. after puttering around i found the centrifigul advance system is working. as far as carbeurator goes, ive adjusted it according to the instructions given to me.
things i found: cylendar 3 was not leaking oil, but unburned gas. upon removing the plug, i found that the spark plug had NO gap and therefore was not sparking. i also took apart the carb and cleaned out every hole.
wouldnt you kno it, ive got it running decentl. i need to get something on it to work it and see what kind of a beast i have created. thanks for the help guys!!