Farmall 400 questions

super99 · Dec 1, 2020

I have a IH 400 gas with a loader on it. No livestock, just used to pick stuff up and load stuff on the trailer. The motor is weak, compression is barely 100#s. It's not worth putting the price of a good overhaul into. I'm thinking about just putting new rings in it and grind the valves so it will start and run better. It carries good oil pressure. Ya, I know, take the block to a machine shop and have everything done to it and then have 3 times what it's worth in it to do it right. Not worth it to me, I just want it to run better than it does now. If I get the head off and the sleeves are trashed, then that's a different story. I'll cross that bridge if I get to it. Can the rear main seal be replaced without splitting the tractor? It probably doesn't get 25 hours a year on it, I'm not donna dump a whole lot of money into it. As long as it starts nd runs better than it does now, I'll be happy.

VicS · Dec 1, 2020

That will.work. I have put oversize rings in. Like.010 just have to check ring gap and maybe file ends a little. Should be able to turn a main seal in. But never worked on a 400.

rustred · Dec 1, 2020

Might not even need rings , u monitoring oil use?how do plugs look? How about just a tune up ? Rear seal is a split.

Hockeygoon · Dec 1, 2020

The fact its maintaining good oil pressure tells me it may not be as worn as you think. Have you adjusted the valve lash lately?

Steve@Advance · Dec 1, 2020

Is there excessive blow by and oil mist blowing out the crankcase vent? Blue smoke under load? Plug fouling? Excessive oil consumption?

If no to these it may only need the valves ground, no need to go into the bottom end.

But if you do feel it needs rings, the old gas engines are forgiving a ring and hone job will buy some time as long as there is no major problem with a piston or liner.

The rear main requires removing the engine unless a 2 piece rubber seal is available. Many times a rear main leak will be greatly reduced if the blow by is reduced and the breather tube cleaned.

fastfarmall · Dec 1, 2020

When and if you do take the head off, you need to measure the cylinder taper, to see if rings will work for you! You should have 130-140 Lbs, of compression to get more horsepower!

pete 23 · Dec 1, 2020

Rear seal is behind flywheel in a two piece retainer so split is necessary to replace.

Rings can take quite a bit of taper, maybe 5 0r 6 thousands but the top ring groove is really important. With new ring max side clearance is .006 with no visible ledge in groove. They can be regrooved and spacer installed above ring.

Piston skirts should be measured to see if any have collapsed . If you see any ridge on bottom of ring travel you are probably done.

I would do a compression test putting some oil in cylinder and if it changes psi considerably you can be sure rings are leaking or better yet a leak down test .

super99 · Dec 2, 2020

I have done a compression test with all of the plugs out, crank it 10 times and get right at 100+s compression on all cylinders, didn't think to add oil and recheck. I'll do that. I put non foulers on all spark plugs and it will start missing from fouled plugs in less than an hour run time. I haven't check the valves yet, I'll do that after I get it cleaned up and it warms up a little bit. It has add on power steering that leaks bad around the torque generator so the motor is covered with oil. It's really cold blooded, when I get the carb set to where it runs halfway decent, it smokes black like it is running too rich. The shaft in the distributor was sloppy, so I replaced the distributor and that helped starting but I'm still not happy with how it runs. I have put off doing anything with it for years, but now it's time to give the old girl some lovin.

Bob M · Dec 2, 2020

Before you get in too deep consider this: I struggled with identical running problems on a friend's 400. Rebuilding the carb, installing a new distributor, resetting the valves, etc. each improved it a bit. But it still ran poorly, constantly fouled the rear 2 spark plugs, etc.

Problem was finally traced to a vacuum leak in the 1-2 intake manifold gasket.

Replacing the both manifold gasket then readjusting the carb got the tractor running like new.

ztrmowers · Dec 2, 2020

looks like you need build waterway instead fill ditch every year, just saying

jimtrs · Dec 2, 2020

(quoted from post at 09:21:44 12/02/20) I have done a compression test with all of the plugs out, crank it 10 times and get right at 100+s compression on all cylinders

.... It carries good oil pressure ..... I just want it to run better than it does now .... I'm thinking about just putting new rings in it

Ummm ..... IMHO I'd be looking elsewhere first.

MeanGene1 · Dec 2, 2020

Considering the even compression and the fact that it runs very little, and just light work, I would do a couple good Seafoam treatments on it, along with a little water in the intake, should get most of the carbon out of it, and maybe loosen up some stuck rings. Also change the oil, and change it again when it shows some color to get the lower end gunk out, might take a while. And like the old CAT mechanics would say, take it out and work it! If that doesn't do it, I'd pull the head and see what the guides look like- for a little-used rig, one can get creative with adapting some valve seals without spending a lot of money. Do the simple stuff first

ss55 · Dec 2, 2020

2X on a leak down test. On each cylinder you can check for air escaping: past the rings into the crankcase; past a intake valve into the intake manifold; past an exhaust valve into the exhaust manifold; and look for bubbles in the coolant. It really helps for pin pointing a problem.

If you compression test numbers are very even but low, it may just be well worn. If you are just replace the rings will you also need to cut out any ridge on the sleeves to avoid breaking the new top rings?

Farmall 400 questions

super99

Well-known Member

VicS

Well-known Member

rustred

Well-known Member

Hockeygoon

Member

Steve@Advance

Well-known Member

fastfarmall

Well-known Member

pete 23

Well-known Member

super99

Well-known Member

Bob M

Well-known Member

ztrmowers

Member

jimtrs

Member

MeanGene1

Member

ss55

Well-known Member

Similar threads