Ford 851 Rebuild?

[Lambosj]

Hi, I have a Ford 851 that I'm wanting to do a full rebuild on this summer. I currently use the tractor to move snow, till my garden and other light work around my place. It runs fine but has been using more and more oil to the point I'm
putting a qt in it for every 10 hr.'s or so of use. No oil in the rad and no water in the old just burning/using it really badly. No over heating ether and the old pressure is good. I drive it a half mile to clean out my churches parking lot
and it'll smoke away to and from. By the time I finish my drive I stink from the tractor. I know I'm going to have to do some work to it and while its apart I want to do a full rebuild as to my knowledge its never been done. I got a ruff quote
from a shop of $1500 - $2500 for a full rebuild and clutch (which it needs too) that didn't include any problems along the way or if the head needed shaved. I wouldn't mind having it done but I would kind of like to do it myself. I've never
done a full rebuild but have been inside of an engine a couple times, (I tinker) and I do my own work to my cars. It was my dads tractor and I would like to do it for the nostalgia of it.

Question is would it be better to have a shop do it or what am I look at if I do do it with the head and new pistons. Better to put new sleeves in or have it bored. I've never messed with having an engine shaved but would there be much of a
point and how would I tell? I what all new bearings, valves, pistons, oil pump, etc done.

Thanks Stephen...

 

[jimtrs]

(quoted from post at 11:26:14 03/12/21) Hi, I have a Ford 851 that I'm wanting to do a full rebuild on this summer......

I want to do a full rebuild as to my knowledge its never been done

Most of these older tractors have already been rebuilt, probably several times

Gasser or Diesel?

If you've never rebuilt an engine, probably could get through a gasser, but might want to sent out if a diesel.

By the prices quoted I'm guessing gasser. They are good prices if for a complete rebuild. You won't do a gasser much cheaper. A diesel should be about 4k -- 5k.

If you do it, Split tractor, remove engine, disassemble completely. Send out for machine shop services - cleaning, inspection, evaluation, etc. They will determine machining. I don't think these gassers use sleeves. The machine shop will determine if cylinders need re-boring, and if so, new piston sizes etc. They measure and grind crank and tell you what size bearings. Have them do a complete valve job. Bring it all back and you do the reassembly, re-install and get up and running.

Haven't checked prices but I'm guessing $1,000 -- $1,200 for machine shop, $500 -- $1,500 parts.

Definitely install a complete new clutch kit while your there. Also front transmission seal. All new belts, hoses, fluids, tune up stuff, water pump, etc. Wiring if needed. Paint your engine before re-install.

THAT's a complete rebuild. You'll spend almost that much doing a partial rebuild and only get half as much. If indeed the engine is worn out, do it all while your there.

IMHO that's more than enough for a first timer.

 

[pomester]

There are operations you can do with a good basic hand tool set and there are operations that need a machine shop.

If I were doing a 'complete' overhaul on that engine, I would disassemble and take the head, block, crank, and rods to the machine shop. Turn them loose on the head to do what needs to be done. Magnaflux and make sure it's not cracked. New guides? probably, new valves?, hope not, new springs? never be a better time. They can put a straight edge on it and tell you if it needs to be flattened. There's a clearance figure on the exhaust valve caps. This is stuff that is difficult/impossible to do on the garage bench.

I'd have the shop remove the sleeves and freeze plugs, clean the block, check the block for a flat deck and flatten if necessary. Install the new sleeves and freeze plugs.

Have the shop mic the crank and assess condition. It may need turned. Pay close attention to the crank and cam gears and replace if necessary.

Have the shop recondition the rods, new wrist pin bushings, check the rods for straight and the big end for condition.

You can inspect the camshaft/lifters/push rods and such, if you see anything suspicious, show the machine shop and see what they say. Same with the rocker assembly.

With everything in good condition, reassembly is pretty straightforward and satisfying. The I&T manual is invaluable.

 

[showcrop]

Before you start you should do a compression test dry, then wet. Since you don't describe other issues, if you have a bad valve that cyl. will be low on the dry test. If the wet test is pretty much the same as dry that confirms most likely a bad valve. If wet gives you significantly higher compression this confirms worn out rings. Usually for a DIY motor job you take it out, strip it down, Take the block, probably with the cam still in it, along with the crank, to the machine shop for cleaning and evaluation. They will tell you what needs to be done and do it if you want. They can also supply bearings pistons and rings that go with what they find and do for you, probably at a lower cost than elsewhere. As for the head it should at a minimum be resurfaced, but you could put it together without doing the valves if there appear to be no problems.