Diagnosis please - sick 656 w/c263 (spark plug pics)

Had to switch to the little tractor last week because the 656 kept losing power after pulling about 150 yards. Turn it off, wait 30 seconds, fire it right back up same thing. I was guessing plugged fuel filter or tank filter or carb filter (but I'd also read on the board that the D21's can be too hot and cause piston swelling so I bought some 18's to put in.)

So this is what I found when I pulled the plugs, doesn't look promising but I'm a parts swapper and not a true mechanic so hoping some of you guys can give me some clues on what you'd tackle next.

The compression test looked much better than what I remember from last time but given how the plugs look I'd say it is because there is so much oil in the rings it's the equivalent of a wet compression test even without squirting in any oil.

#1, #2, and #3 left an oil patch where I layed them on the concrete.
#4, #5, and #6 were 'dry'?

Oil pressure after warm shows to be about 22.

If she needs a top end I have to start now to beat hay season. Thanks for help.

I do not think that you are going to like what i have to say here . First off the hot oil pressure is on the bottom of the totem pole (not good) from the looks of th plugs yep ya got oil COMING UP not good . Doing a head job is not going to cure this . With low oil pressure the bottom end is just about toast so ya are going to probable need bearings and more then likely regrinding the crank , also new cam bearings . On the oil pumping i would have to say that either ya have scored liners and pistons on the holes in question or stuck oil rings. This is cause by running reg gas and causing the pistons to swell So i guess you are looking at a total out of chassie rebuild . If you want life out of any of the later 4 cyl. and 6 cyl. gas farmall this is what ya have to do . 1 ya run high test , 2 ya run low ash 30 weight oil 3 ya run the plug that was meant to be in it as to the heat range. , 4 ya set the ing. timing to spec. and check it with each and every point change. , 5 ya make sure that you have good fuel flow from the tank to the carb and never put a inline filter in the line the screen in the sediment bowl will get the job done and make sure that ya keep that sediment bowl clean of water and junk. Keep in mind that these tractors were build when gas was rated 95 octane for reg. and the min. fuel requirement for these engines is 93 . If you decide to rebuild then there are things that you or your machine shop need to know and i can help on this.

The oil fouled plugs indicate that you have a serious problem. A cylinder leakage test will pinpoint where the problem is. If you apply compressed air to the cylinder with a cylinder leakage gauge, you will hear the air escaping to the crankcase (bad rings, piston, cylinder), to the intake manifold (intake valve), exhaust manifold (exhaust valve), or cooling system (head gasket/block). The oil fouled plugs would most likely indicate a problem with the piston rings or piston. Excessively worn intake valve guides could also cause oil fouling but not to this extent. A good reading for a cylinder leakage test is 90% (i.e. if you apply 100 psi the cylinder would hold 90 psi). Anything lower than this indicates a worn engine and major engine repairs.

Tractor Vet stated "do not think that you are going to like what i have to say here"

...Nah, that's OK, I kind of figured she'd be close to needing her overhaul based on what I've read on the board (gas = 5,000 hours, diesel = 10,000?) Doubt I've put more than two hundred gallons of gas through her since I bought her two years ago. I've run 93 octane (but not the low ash oil). No idea on what the prior diet consisted of. I did put a gas filter on it but I think I can remove it now. Magnets in the tank and sediment bowl seem to have gotten the crud out. Came with a very nice loader with very little use. I got a great deal on the tractor because no one could get the loader to work consistently (turned out to be a coupler!) I'm in it right so spending some cash is ok.

I have begun the tear down. So far I'm impressed with how easy the components are to access and to remove. Much easier and less time involved than some car engines I've pulled in the past.

While pulling off the intake found this hole in the feed to the carburetor. Makes the air cleaner kind of irrelevant.


Top end seems clean enough. I was expecting a little more varnish/sludge. Guess it doesn't get very hot up here.


Victor head gasket indicating someone's been in here prior?


Generally the condition of each combustion chamber resembles this one


No scoring in the cylinders. #5 and #6 have a cylinder ridge; my guess would be thickness of the ridge is about the thickness of sheet of 20# copy paper. (I can just hook a finger nail on it.) Ridge in #1 and #2 is almost nil.


Is this an original piston? Or, at 4360 hours will this be the 2nd rebuild?


Bottom end also seems clean enough.


Rod bearings shot. Presuming cam and mains are in similar condition


Except for any work the head will require I'd like to do everything myself. With the money saved by not regrinding the crank or having it line bored seems like I'd have enough to replace the clutch. Not trying to be penny wise and pound foolish but I do need to be effective.

Now that we've confirmed the condition of some of the components what are Tractor Vet's and everyone else's thoughts for rebuild options. At a minimum??? At a maximum???

Can I plastiguage the crank and put in oversize bearings if necessary with out a regrind?

"If you decide to rebuild then there are things that you or your machine shop need to know and i can help on this...." I'm listening