Farmall 806 Manifold Heat Control Valve

meborder

New User
Hello all!

just registered in hopes of getting some help with my new-to-me Farmall 806. It seems like everytime i have a tractor question and do an internet search i always find some good information on this site, so i figured i might as well become a member ... it's not like i'm ever not going to have a tractor (or two), right?

my 806 starts great and runs well .. for about 20 minutes, then it noses over and tries to die. after much searching, and talking with the shop guys at the local Case dealer he directed me to the manifold heat control valve. his experience shows, and internet threads confirm, that these are a know issue for a tractor that runs well but noses over after a short period of time.

So i've "rebuilt" the carburetor (got a kit at TSC and used as many of the parts as fit) and that went well (it started and ran well tonight after reassembly), but i'm unsure how the manifold heat valve is supposed to be oriented.

i found the valve weight partly stuck in the "down" or "rearward" position. i got it free'd up so the weight swings from vertical to the rear, or "down" position. the engine runs well with the valve held by hand in both positions. The shaft is connected firmly to the weight and the spring moves when the weight moves. now, whether the valve is properly attached in the manifold is anyone's guess, but i have to assume it is at this point because it didn't take much to get the assembly to move rather freely.

which way is the valve supposed to be when the engine is cold? it seems like it should be vertical, and the spring should relax as it warms up letting the weight fall to the rear. If this is the case, it appears that i may need a new thermostat spring as it doesn't appear to have the ability to hold the weight "up"

am i on the right path?

thanks in advance for any help.
Mike
 
took me forever, but i finally found a picture of the old beast.

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When the engine is cold, that's suppose to deflect the heat up to the top of the carbruetor to help vaporise the gas so it doesn't spit and sputer, then when the engine get to operating temp, Its no longer needed.
 
(quoted from post at 23:27:02 05/19/15) When the engine is cold, that's suppose to deflect the heat up to the top of the carbruetor to help vaporise the gas so it doesn't spit and sputer, then when the engine get to operating temp, Its no longer needed.

The right idea. Just a minor detail in the description, since this tractor has an updraft carburetor the exhaust has to be deflected down into the intake manifold rather than up.



mvphoto21115.jpg
 
Did you ask your number one ace mechanic? Bet he has an answer, cute little guy. Tractor looks
like she still has quite a bit of life left in it. Is the carb getting a good flow of gas? If you have been
hanging out here a while I'm sure you have read about trash and floaty things in gas tanks that
like to plug the sediment bowl inlet.
 
(quoted from post at 22:54:19 05/19/15) Did you ask your number one ace mechanic? Bet he has an answer, cute little guy. Tractor looks
like she still has quite a bit of life left in it. Is the carb getting a good flow of gas? If you have been
hanging out here a while I'm sure you have read about trash and floaty things in gas tanks that
like to plug the sediment bowl inlet.

i haven't checked that yet, but it's on the list. before i thought about it i already had the carb off so i gotta drive it back up to the garage so i can blast a little air up through the sediment bowl.

i don't think that's the problem though. the last that that happened (on the massy) it would nose over as soon as the governor applied power regardless of engine temp and the choke wouldn't help save it from stalling.

but it is something i will check for sure.

thanks for the compliment. it has 5800 hrs on the clock but runs like a champ. we got it from my wife's uncle who bought it on his neighbors estate sale. it has just been and acreage tractor and ran a snow blower in the winter for the last 20+ years, so it hasn't had the snot worked out of it for quite some time.
 
(quoted from post at 20:27:02 05/19/15) When the engine is cold, that's suppose to deflect the heat up to the top of the carbruetor to help vaporise the gas so it doesn't spit and sputer, then when the engine get to operating temp, Its no longer needed.

yep.

but which way deflects hot air toward the carb?

weight up, or weight down?
 
The counter weight should stand straight up and down when cold and move toward the front of the tractor when hot. This puts the plate shown in Owen's diagram near straight up and down with the counter weight. In that position the exhaust is directed through the so called stove on the manifold,(the square looking section ) so the air passing through the intake will be heated for better vaporization of fuel. When hot, the counter weight should lay down forward, plate will be blocking most of exhaust from entering the stove. Normally the problem is getting enough heat because the control valve is burned out inside along with the internal passages being plugged that surround the stove and whole mechanism being stuck. That requires manifold being taken apart and cleaned and rebuilding the valve mechanism according to the instructions.
 
(quoted from post at 10:10:04 05/20/15) The counter weight should stand straight up and down when cold and move toward the front of the tractor when hot. This puts the plate shown in Owen's diagram near straight up and down with the counter weight. In that position the exhaust is directed through the so called stove on the manifold,(the square looking section ) so the air passing through the intake will be heated for better vaporization of fuel. When hot, the counter weight should lay down forward, plate will be blocking most of exhaust from entering the stove. Normally the problem is getting enough heat because the control valve is burned out inside along with the internal passages being plugged that surround the stove and whole mechanism being stuck. That requires manifold being taken apart and cleaned and rebuilding the valve mechanism according to the instructions.

thank you!

I think this answers my question, but with only one small exception. the weight on mine moves from straight up to rearward. that is to say, the "down" position is toward the cab.

not sure if maybe mine got installed wrong at some point in history or not, but I'm going to reassemble it tonight with the counterweight straight up. I got a new thermostat spring today from the local dealer ($53) so hopefully this will cure what ails her.

as easy as it was to get the damper moving, I'm just hoping that the rest of it isn't plugged up. If it is, I'm going to see about just getting a new manifold rather than have all the down time while I get the existing one cleaned up and working.

I'm hoping it won't come to all of that, though :)

thanks again for all the help.
 
Take a close look at the diagram to see how your slot where the spring hooks up. It has to be in that relation to work properly. Hard to tell if it was installed wrong as I have seen them so messed up I could only guess. I even put on a whole new manifold for a customer a couple years ago, completely assembled and it was totally wrong. Took it apart to redo it. It was the second one we got as the first one the weight was busted off in shipment. The valve inside cannot go back the wrong way if assembled right. It might be that the weight itself came loose from shaft and some one welded it on and got it wrong and valve inside is actually ok. If I could feel it I could tell you but can't from here.
 
(quoted from post at 20:22:39 05/20/15) Take a close look at the diagram to see how your slot where the spring hooks up. It has to be in that relation to work properly. Hard to tell if it was installed wrong as I have seen them so messed up I could only guess. I even put on a whole new manifold for a customer a couple years ago, completely assembled and it was totally wrong. Took it apart to redo it. It was the second one we got as the first one the weight was busted off in shipment. The valve inside cannot go back the wrong way if assembled right. It might be that the weight itself came loose from shaft and some one welded it on and got it wrong and valve inside is actually ok. If I could feel it I could tell you but can't from here.

i think something is really wrong with mine. i got a new spring and put it on, but no matter how i install it i'm left with a "does nothing" proposition.

the way the shaft is keyed, if i install it "correctly" as per the diagram above, then the spring is loose and the weight falls all the way to the rear of the tractor with no way for the spring to pull it forward.

if i install it the "wrong way" then the spring is wound so tight that it pulls the weight forward to the top and as it heats up, the spring just pulls it tighter.

all of this wouldn't bother me, except with the weight all the way down it ran like crap, and with the weight all the way up, it still ran like crap.

I REALLY don't want to pull the manifold(s) ... but i'm not sure what other options i have at this point. it just doesn't run well.

the motor is just really lazy, and wants to die under throttle when warmed. it's lazy to the point that the motor will nearly stall when i try to get rolling ... just no power. the rpm's really drop when you start adding a load. it also takes a long time to respond when you add throttle.

FWIW, i checked the timing and it was too far advanced. i set it to 22-24°BTDC @ high idle (was running 30+ before adjusting it) but i haven't had a chance to see if that helped. i'm doubtful that it will.

i'm open to any ideas. but i'm thinking it's been messed with much as you describe above.
 
I don't like to commit unless I am sure but. IMPO I have never had a farmall that the heat valve worked. I don't think you would see any change in warm weather one way or the other. On pulling tractors we remove them first thing. I think it has to be fuel flow. Those carbs are just big enough and that's about it. If not enough flow it will slowly suck the bowl dry. Making it weak on power and then falling on its face til it dies, 20 minutes or so, faster under a heavy load. If you have good flow to carb the problem could be at the needle & seat. That is were the smallest hole is and that is were the problem is on engines that have been built for pulling. Just my two cents worth and with all due respects to everyone else that is trying to help you. You have some pretty good men here.
 
(quoted from post at 22:00:51 05/21/15) I don't like to commit unless I am sure but. IMPO I have never had a farmall that the heat valve worked. I don't think you would see any change in warm weather one way or the other. On pulling tractors we remove them first thing. I think it has to be fuel flow. Those carbs are just big enough and that's about it. If not enough flow it will slowly suck the bowl dry. Making it weak on power and then falling on its face til it dies, 20 minutes or so, faster under a heavy load. If you have good flow to carb the problem could be at the needle & seat. That is were the smallest hole is and that is were the problem is on engines that have been built for pulling. Just my two cents worth and with all due respects to everyone else that is trying to help you. You have some pretty good men here.

i think you may be right. i had a few minutes here tonight and pulled the sediment bowl off and checked the flow coming out. was coming out at a moderate trickle, so i blasted the tank outlet with some compressed air and after a couple shots of air i nearly took a bath in gas.

so if that isn't "the" problem, it was certainly "A" problem. it was getting fuel, but must have been draining the carb over a period of time, just like you said.

we'll see this weekend. i'll give it a run and see what it does. hopefully this will fix the overall lazyness i've had since i got it too. we'll see.

thanks for all the help from everyone!
 

it appears to be fixed, or at least pretty darn good.

i warmed it up and took it for a drive down the road and it never tried to die on me, so it's at least good enough to use.

i'm thinking i've got the manifold valve in a position where it is doing a good job of warming up the intake too. i checked it with my IR gun and the exhaust was running anywhere from 350-450 surface temp, and the intake was running as high as 200ish right below the valve, and 100ish out at the end of the runners to cyl 1/2 and 5/6. I know it isn't "right" but it seems to be "good enough" even if only for now.

interestingly though, right above the carburetor it was running about 40 degrees with some visible frost on the outside of the manifold. so the manifold heat appears to be quite necessary. the ambient temp outside is in the low 70's, so the manifold can take quite a bit of heat without causing any problems.

i'm leaving well enough alone at this point.

thanks for all the help!
 

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