tractor engine top end rebuild

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liveaboard
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Re: tractor engine top end rebuild

Post by liveaboard »

The tractor is Italian; I don't know where the ring compressor tool was made, but the fasteners and screw are of Imperial measure.
In any case, it did its job; I might never need it again, but it's in my toolbox just in case.

I use copper grease on all the fasteners; except the exhaust nuts. My experience is that it won't survive the heat.

At the bottom of each cylinder where it rests on the block, there is a thin steel shim or two as required to get the correct piston height. Well, cylinder height really. One is 0.5mm thick and I had to use another of 0.25mm on each. No sealant, no rubber, nada.

How this keeps the oil inside is a mystery to me, but I'm assured that it works.
The top of the piston should be 0.3 - 0.5mm below the top surface of the cylinder (at TDC of course).

The head gasket is just a thin flat copper washer. The cylinder has radial ridges to press into the copper, the head mating surface is smooth.
All expansion is absorbed by the 5 long studs on each cylinder. the threaded sections are larger section than the length.
The heads and barrels are cast iron.

This sort of motor is new to me, but people I know have been tearing them down and building them up for a long, long time.
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Bill Shields
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Re: tractor engine top end rebuild

Post by Bill Shields »

The bottom of the sleeve will not leak because there is no pressure there, as opposed to the top.

My BMW air cooled cycles had nothing between the cylinder and the crankcase except a nice finished surface.

It is little more than an overgrown air cooled VW engine -> a tried and true design.

Didn't Deutz do something similar in Germany?

I am sure you know this, but the head gaskets are one and done without an annealing, they are prone to leaking.

The working diameter of the stud, along with the material, is a significant part of the calculation, as is lubricated threads during torquing.

Some companies even specify the lubricant to use on the threads and washers as it effects the overall calculation.

Something you may want to (probably have) check -> the leaking cylinder head -> is the sealing surface FLAT?

Have you considered one of the nickel based high temp compounds? Not sure if they are good for higher temp then copper..but may be.
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LIALLEGHENY
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Re: tractor engine top end rebuild

Post by LIALLEGHENY »

Not that your going to do it now, but many manufacturers recommend replacing head bolts / studs when rebuilding an engine. Each time you torque them down they stretch, they are designed too. With each consecutive torqing they stretch even more, and before you know it they have stretched to the point that they can no longer be torqued to specs. They may even break. I can attest to this from experience.

Nyle
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Bill Shields
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Re: tractor engine top end rebuild

Post by Bill Shields »

Nyle is correct -> in had completely forgotten about that aspect (getting old and has been 40 years since ripped a gas turbine apart).

Does the manufacturer list a nominal length -> beyond which you toss the stud?

I seem to remember that Mitsubishi also used to specify a minimum diameter of the turned area-> below which the bolt would be tossed.

And BMW used to specify that the flywheel bolts were "use once and throw away".

Most of us did not...except maybe the racers...
Too many things going on to bother listing them.
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liveaboard
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Re: tractor engine top end rebuild

Post by liveaboard »

I haven't read the entire repair manual, but I didn't see anything about stud length; I torqued them all to spec successfully though.

Providing they were not stretched beyond the yield point, they should be the same length as the day they were made; however, if one does break it will be visible.

I did not check for flatness; I probably should have. the spigot shape makes it difficult.
I suspect that the previous person who assembled the engine was not very good at it. There are signs, like silicone seal smeared around O-rings. so my working theory is that it was not correctly torqued.

Anyway, if a cylinder leaks or a stud breaks, I'll just pull it apart and do it again; no use stressing about bolt stress now. It's a tractor, it moves slowly and doesn't go far from the workshop.
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Bill Shields
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Re: tractor engine top end rebuild

Post by Bill Shields »

Silicone on O-rings is a sure sign of inexperience.
Too many things going on to bother listing them.
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liveaboard
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Re: tractor engine top end rebuild

Post by liveaboard »

Lots of signs of bad work on the tractor; not to mention the terrible wear on all the linkages and steering parts due to a lack of simple lubrication.
I had to replace every joint and bushing on the tractor, and there are a lot of them.

Something obvious after the mistake has been made; to get the heads all in one line, it seems that it's necessary to attach the intake and exhaust manifolds before torquing the head nuts. The spigot heads can rotate slightly before tightening, so the ports were not in line.

It's not in the repair manual, but it seems obvious (after the fact).

So I released the tension, bolted the manifolds on, and then tightened the head nuts again. I know I should have taken it apart and put in new head gaskets, but I didn't.

Hopefully, it will hold.
Last edited by liveaboard on Tue Mar 26, 2024 10:08 am, edited 1 time in total.
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Steggy
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Re: tractor engine top end rebuild

Post by Steggy »

liveaboard wrote: Mon Mar 25, 2024 6:28 pm At the bottom of each cylinder where it rests on the block, there is a thin steel shim or two as required to get the correct piston height. Well, cylinder height really. One is 0.5mm thick and I had to use another of 0.25mm on each. No sealant, no rubber, nada.

How this keeps the oil inside is a mystery to me, but I'm assured that it works.

As long as there is little-to-no crankcase pressure when the engine is running, the seal between the shim(s) and the two surfaces with which it is in contact will not leak—assuming of course the mating surfaces are reasonably smooth and flat.  BTW, that sort of sealing arrangement is fairly common with air-cooled engines that have removable jugs.
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NP317
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Re: tractor engine top end rebuild

Post by NP317 »

I have followed your top end rebuild with interest. Working on an air cooled engine is different.

The Hood River (Oregon, USA) Museum I volunteer at has several Franklin automobiles with vertical 4-cylinder forced-air cooled engines.
They all operate and provide rides for visitors. And now I have an increased appreciation for potential maintenance on those machines.

Thanks for sharing your work.
RussN
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Steggy
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Re: tractor engine top end rebuild

Post by Steggy »

Bill Shields wrote: Mon Mar 25, 2024 9:51 pmAnd BMW used to specify that the flywheel bolts were "use once and throw away".

Most of us did not...except maybe the racers...

Any time I removed the clutch and flywheel from my race car’s engine, I replaced the fasteners.  Take it from me: there’s nothing quite as exciting as have the clutch and flywheel assembly cut loose from an engine spinning at 8000 RPM.  Been there, done that...once.  Fortunately, the scattershield send the debris downward, instead of through the floor and yours truly.  :shock:
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hydrogen18
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Re: tractor engine top end rebuild

Post by hydrogen18 »

That's a neat project. I work mostly on motorcycles from Japan, so I've never repaired anything that used individual cylinders other than once helping a friend with his Volkswagen. My limited understanding of head studs is that not all of them are torque to yield. I know at least one person who rebuilt a small block chevrolet without replacing the head studs. But that's a single casting engine.

Is this a diesel or gas engine? I think I see an injection pump there.
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liveaboard
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Re: tractor engine top end rebuild

Post by liveaboard »

Very diesel; gasoline tractors are pretty much unknown here.
I sent the injectors out for testing, one needed repair.
I'll push some fuel through the pump and blow out the lines before reassembling the fuel system.

I got sidetracked by some errands and the need to make an oil pressure switch adaptor (I can't get a new switch with the right thread). Hopefully I'll have the engine running in the next couple of days, then I have to replace the steering bearing seals and fix a brake problem before I take it out to get some yard and forest work done.

The repair book does not say anything about replacing the studs; it's a tractor after all, not a performance car.
The heads and barrels are cast iron, the pins and bearings sized for longevity.

I found the exhaust manifold nuts are stainless, but the studs are not. I had all the hardware in a magnetic dish and the nuts fell out.
One is yet to be found.
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