Engine block cleaning at home isn't that much different than engine block cleaning in a shop, you just won't have any fancy specialty or automated equipment. Pressure wash the worst of the sploooge first (steam cleaning would be even better). A pro machine shop would either hot tank it (caustic soda) or bake it at a really high temp. Of course you'd have to make sure it was nothing but bare iron first. This is followed with the first phase of washing with hot soapy water. Blow dry with air.
A shop may shot blast it next (obviously you don't have that in your garage) to take off the rust. Any machining is done at this point.
Before assembly, it gets a thorough wash, again with soapy hot water. Test tube and bottle brushes are the key to getting into all the passageways (including valve guides). Wash it thoroughly and when you think you are done, START OVER and do it again. Normally in a shop a wash station is set up with hot water pressurized by shop air--you don't have that luxury at home, so use a large rubbermaid tub and keep changing the water. Don't stop until it is uber-clean! That is far more important that worrying about pits on a 40 year old camshaft etc. that you will go crazy trying to find a replacement for. Remember with engine building, Cleanliness is Next to Godliness!!
After you are done washing it dry it with compressed air. Spray a light oil of your choice on a rag and wipe down the bores and machined faces. You can paint the outside of the block too at this point if you choose.
Knurling is a common process in machining though I'm not sure how many automotive machine shops can still do it--it was more common there in the days before replacement press in guides or bronze guide liners were available.
You've seen knurling done before on things like knobs and handles to give you grip. This is the process that gives that cross-hatch or inline series of grooves. Its generally done by turning in a lathe, not really sure how they do guides but I'm sure the premise is the same. Knurling presses ribbed, hardened steel wheels into the softer metal. In doing so it "squishes" the surrounding material outwards. In the case of a guide, it makes the inside diameter a few thou smaller while leaving grooves to hold oil for better lubrication of the valve stem. It is kind of hard to explain without seeing it.
Back to internal conditions of the engine, if the parts are not available new, or not reasonably priced, you are going to be forced to make do with what you have. Keep in mind this is a lawnmower engine that doesn't even see 4000 rpm, not a race engine that is spinning at 8500rpm.
Things like the crank journal can be reground if it is bad, but if it is within spec and even if it has a few pits etc. in it you can give it a rubdown with crankshaft polishing paper.... its like a really fine emory cloth. The pits themselves don't really hurt anything, its any microscopic sharp edges that may be protruding that can hurt things! Polishing it well will remove any traces of that, and the remaining pit if anything will end up full of oil--keep in mind they are microscopic.
Camshaft is the same way. Hopefully you kept everything in order when you dismantled it so the parts go back in their original places. Valve springs fail from (among other things)high heat and high rpm. You won't see either in your JD. If they are available cheap, grab new ones, if not, don't lose any sleep worrying about reusing what you have. Same with things like valve locks/keepers/etc. Inspect them thoroughly and see how they fit on the valve loose in your hand. The only way a valve lock is going to fail on you is if it shears off that little key--you don't have the spring pressures for that unless there is already something wrong with the locks, in which case you'll need to replace them AND the valves because they will have worn too and won't fit tight. If you can't see anything wrong with the locks and they fit nice and tight reuse them! By its tapered design, a valve lock only grips tighter under pressure from the spring... it's not going to let go if it is installed right.
Rings should be available no problem, you don't need oversize unless you bore the block. The crank bearings can be changed if they are available but in most cases really aren't necessary unless there is play in them... they are in an oil bath so chances of failure are not very high. Did the crankshaft oil seals leak alot? That can be an indicator of bearing play. How do they feel? You can make your own judgement call based on that.
Replace seals and gaskets. Make sure the seals haven't worn huge grooves in the crankshaft surface too. Polish these areas too. Offset seals to help correct that problem are available for many axles and engines etc. but somehow I doubt your Tech is in that list.
Unless I have completely misunderstood your intentions, what you are looking for is a fresh looking and good running little tractor, not a showpiece. It can be very easy to spend $10k on a machine worth $2k so you have to balance your priorities. Things like not boring the block or grinding the crank if they are within spec are what I'm talking about--where others will tell you it is manditory. It's not. It's real easy to spend other people's money!
You can get many many more years of service on a 'working quality' restoration without breaking the bank. If you make it too pretty you won't want to use it anymore! lolYou are more than capable of doing all of this at home on a meager budget, and chances are that by the time you need to tear down the engine again, the rest of the tractor will also need to be gone over again, the joys of anything old!
Just my opinion, for what its worth.
:drunkie:
