Case 400 missing

[dgrewe]

I am at a lost.....
My 400 is not firing on cylinders one and two and I don't know why??? I gave her a complete tune-up, new plugs, wires, cap, etc.
Still misses, next I rebuild the carb, no difference, took a compression test.... all four cylinders are within 110 to 120 psi.
Don't know what to do next??? The confusing thing is when I accelerate, she hits on all fours, same when under load or going up hill, but driving on level ground she sound like my '41 JD B. Any ideas what I should do next????

 

[oldproudvet]

Double check your firing order, and rotation, on the cap. Easy mistake to make

 

[chuck machinist]

If you made your own plug wires to length, check your crimp on the end.CM

 

[DKase]

Check intake manifold and manifold gaskets.

 

[Lpakiz Larry]

My 400 was very susceptible to carbon dust shorting out the plug. Just running it over-choked for 15 seconds would foul a plug.
The plug would be dry, just dusty. However, when fouled, it wouldn?t fire at all, under load or not, so not sure this helps you.
Usually could swap the non-firing plug with a good one from another cylinder and it would clear up.

 

[ss55]

Do cylinders #1 & #2 share a common intake manifold runner? If it's only missing at idle and light loads, I would check for an intake leak ahead of those two cylinders.

 

[L.Fure]

All the 400's I've owned would foul #3 and #4 if I choked it too long, and didn't run it long enough to heat the plugs up. The old trick used to be to pull off one of your lapel buttons and stick it in the plug wire boot edgewise. That would hold the plug wire just the right distance to make the electricity arc to the plug. This would keep the plugs from fouling. I learned this from an old WWII vet that would do this to keep the jeeps from fouling out the plugs.

 

[jon f mn]

Those cases are very particular about plugs, especially champion plugs. I would try another set of plugs, at least in those 2 holes.

 

[mEl]

What those others said about the intake manifold gaskets!

 

[CHUCK CAMBIS]

I had the same problem on farmall 404. Weak valve springs. I did not discover the answer for over two years. Has ran great ever since.

 

[kevinthefixer]

To check for manifold leaks, let the engine idle, and take a can of brake cleaner or WD40 with a straw, squirt a tiny bit at any possible leak, along the gaskets, any irregularity in the casting, and at the throttle shaft. Any significant change in the way it runs and you've found a leak. Don't assume there's only one, go over the whole thing.