Ford 800 Head

I decided to replace the rings on my Ford 800. I have never done this type of job before. Do I have to have the head machined before reinstalling?

You should have the head checked to be sure its bottom surface is level.And i would also have the valves and seats refaced.

Rings may just be a band aid fix ,why not do it right the first time and install new sleves and pistons and bearings you will be money ahead in the long run

My impression of this post is one of near amazement.

Why should you just decide to replace your rings?

You may just want another job to do in the winter months, an exploration job, who knows!

There may be some reason(s) why you think they should be replaced.

From your post you don't seem to have the expertise to do this job effectively.

You will need to dismantle and check all parts for wear, damage and seviceability. There is no point in fitting rings to a bore which will not accept them or to pistons which are unseviceable. You might find, if you look, that the crank is at or near the unserviceable limits of wear. When the head is removed the valves and seats and guides should be checked, measured and reseated as necessary. These are all standard jobs lumped together as the work in doing each separately would be mainly duplication of effort, wasted time and resources. That is, unless they have been done recently. The head surface should not need machining, but you check it and machine if necessary.

Furthermore, you need to know the types of ring that can be used for this purpose. You may need to remove the ridge at the top of the bore, although this often indicates other problems for this particular exercise.

Gas, diesel? Are there other possibilities you have overlooked for the dfciding to replace the rings? Have you carried out a compression test to ascertain differences between cylinders? Is the oil pump, pressure reief valve good? Are main and big end bearings good? If pressure is being lost you need to know where to look for problems and fix them all at the same time -for two reasons - 1) you will be stressing other parts which may be near to failure and 2) you may well be repeating the same dismantling work again in short order.

As other poster suggested, an complete over-haul kit of liners and pistons might be a better route to go. I say find out first and then decide which route to go, but bank on the worst scenario situation and you won't end up trying to cut corners and finish up with a poor or ineffective repair.

Regards, RAB

You should have the sleeves checked for taper too. but once you pull them out you need new ones.

Near amazement??? I thought I had a cracked piston in one cylinder since under stress oil would spray of of the breather. It seemed that the oil pan was getting pressured, and that one spark plug was all cruddy. Not only that but the oil smelled like gas, and when the tractor was running there was black smoke coming out.

Its not like the tractor was sitting there and I thought, Hmmm lets waste a bunch of time and tear this down for the &^*% of it. This is exactly why I use caution posting on this site. There is always one person that make you feel real "good" about yourself.

why are there so many angry old men at the tractor forums?

I'm with Leland. You can make this tractor go another 50 years with a $450 engine rebuild kit and a few hundred dollars in machine shop work, more if you run into unexpected problems. That way you won't be second guessing yourself when you get it back together.

If you do decide to just do enough to keep it running for now, which is a valid, but riskier decision, your local machine shop can inspect the head and give you an opinion on condition. If it needs work, a valve kit is under $100 on this site, and the machine shop should do the head work for another $100 or so if the head isn't cracked. If it's cracked, add another $100-$300 to have it 'stitched' up. Ford 134/172 heads are known for developing cracks around the exhaust valves (I just had a one reworked, total cost $425). See attached picture and closeup of stitched cracks.




Before you reassemble, check the major wear components (cylinder bores, pistons, crank bearings, main bearings, and oil pump). If you put new rings and a valve job on an engine with a weak lower end you will hasten the weakest points failure.

Good luck and keep us posted.

Not sure why such a grumpy response, what he is saying is to do the job right, that is once you determine that 172 4 cyl is worn, and you want to do a rebuild, it's best to do a complete job if possible, all the measuring is going to confirm what you have, then you can determine what is out of tolerance, what to do to correct it, which may entail a rebuild. Some of those 172's are sleeved/ have liners, I think the earlier ones with a diamond on each side of the serial number above the starter, on the flat spot on the transmission.


Now you have shed some light on something and no one has responded to the gas odor in the oil. Gasoline thinned oil will cause damage, oil is thinned out, depends on how much gas, but with excessive carbon soot out the stack, you have a fuel system issue, maybe it's not thinned enough to cause a failure, but it could be accelerating internal wear very easily. Not sure what this engine does when out of time, I'd check the timing as well. Thinned oil is going to get past the rings, could wash the cylinder bore, not an expert but it's not good, not sure if it could glaze the cylinder bore, then the bottom half, engine main bearings and gas thinned oil not a good comination, solve the fuel problem with the carb, change that oil out and see how it runs.

Aside from the valve and seat, the mating surface of the head should be checked to see if it is warped, and you may want to have the head magnafluxed to check for cracks, hairline fractures, prior to reinstalling. Again, not an expert on any of this, I've seen bad results from just doing the top half of a motor, where things are mismatched, compression comes up, engine gets worked hard, but the lower half is worn and can't take it, and fails. Lot of variables with this, so once you take something apart, I think it's a good idea to do the right job, measure all components and know what is what.

not angry. Just never really amazed at the posts.

Your post said enough to leave anyone making a response just guessing.

Patently, if you thought you had a cracked piston, you were not just going to replace the rings! Now we need to know how long this cylinder has been allowing fuel into the sump (something else you didn't mention). Sounds as though it might even have been running on 3 pots?

You got a measured reply for an inadequate posting.

Sorry for the crappy reply earlier. I was not aware of all the things that must be checked to make sure the work goes as planned. Now after talking to some mechanics (should have used one)I understand why if you going to part of the job you might as well do it fully and right.

Sorry!

I am going to take the head in and have it looked at. Now about the crank shaft.I am going to look at the bearing. If they are not work should I have the crank looked at?