cyl bore tolernaces - follow up to mashed push rods

[denchen]

Im wondering, what went wrong with the engine. Alloy on the cylinder wall, crank and head to a machine shop and now camshaft bearings. I might be a bit bias, but Perkins make good hard working, trusty engines that keep on going even if sometimes with rattles. Perkins have made engines for other companies for many years. Massey Ferguson, and Ford used to use their engines but with their own names on. Other companies do the same naming. Going back to your engine, was the wrong oil used, or an oil pump failure or has something else gone wrong.

 

[TractorGuy]

Yes, this was my first gut reaction as well, but then I start thinking about it, and as has been pointed out... what is the additional cost in the grand scheme of things to have it done to the best degree possible? The answer is, its about 500-700 for the block work and I also have to do something about the cam bearings (which the machine shop will deal with, but nothing is free). That's not insignificant, but its also getting the block to the machine shop, 4 weeks lead time, repainting it when it comes back, etc etc.

I have a machinist straight edge and I have checked the deck on the block and I can't find any gaps with a .001" feeler gauge.

Thanks for the great feed back from everyone. My intention is to put a grapple on this machine and use it for a year or two cleaning up about 20 huge pine trees that have fallen and were felled at my rental property. Then I will probably sell it. I have a decent size Kubota tractor for general purpose stuff. If I end up keeping it, I think I would be hard pressed to put 20-30 hrs a year on it. I have owned my Kubota for more than 10 years and I think I put around 500-600 hrs on it.

But regardless of how I use the machine or what I end up doing with it. Since I am going through the trouble of rebuilding it, then I am going to do so with the expectation of getting 3-4k hours out of this engine again. And its not just the cost of the block work. I own a machine shop and I know how difficult it can be to hit high tolerances - all it takes is a little tool chatter and you are screwed. And I don't know anything about the auto machine shop I am using, except that he was recommended by a car engine place because they wont touch diesels.

I am leaning toward trying something to get the aluminum off and honing it... I feel like the devil you know....

clint

You haven't responded to your other thread in a while so I'm not sure if you have read the other opinions there. I am copying one of your photos from that thread into this one to continue making a point.

As I said earlier if you don't figure out why the valve contacted the piston and correct that issue everything else will be for naught.

In this picture it appears the valve contacted the piston to the left of what looks to be valve reliefs that were cast into the top. IF that is what the depressions were for it could be the engine had been apart and someone installed the pistons backwards. Pistons HAVE to go in facing forward as defined in your service manual. They may also have to be on the connecting rod a certain way. You may not know this but the wrist pin is actually offset in most pistons with the longer side of the piston to the thrust side. It is very slight but if you pull a tape around on both sides you will find the difference.

Make sure you figure out how the piston goes on the connecting rod and which direction it should face in the cylinder before you put it back together.

 

[clinter36]

That seems to be the million dollar question....

This engine appears to be a Shibaura as it has a Shibaura tag on it However, Shibaura and Perkins had a joint venture on these small engines for 20 years. In fact a few years ago Cat/Perkins bought out IHI Agri-tech - which was or includes Shibaura. I think maybe 30-40 years ago you might be able to classify an engine or machine as "good quality" based on the reputation of the manufacturer (CAT, case, Deere, etc) and we all know some manufacturers had stronger and weaker traits.

Anyway here is what I know: Both push rods on the number one cylinder are bent and there is clear evidence (there is a pic in mashed pushrods thread) that at least one valve in that cylinder hit the piston. All 4 pistons are pretty well scored.




The machine shop looked at the head and said right away he can tell the head gasket was leaking. He said when the head gasket leaks, "it heads for the cooling passages and pushes the coolant out and they overheat. That's what happens to these engines." We discussed the push rods but he didn't seem to have much to say about it. I asked him if the thought the deck of the block would be warped and he said probably not, but check the cylinders for roundness, they come out of round when they overheat.

I did check the block and it looks good. The cam shaft is excellent and within factory spec, the crank/rod bearings all looked good. The only other weird thing I found was the oil pump shaft is worn quite a bit on the top surface only. I looked at the pump cam thing briefly and it looked fine.

So bottom line we have: Bend push rods (cyl 1), Valve contacting piston (cyl 1), Scored pistons, worn oil pump shaft. And that is all I could find for damage.

 

[dodge man]

Could be it hydro locked a little bit? The valves could not open all the way and the push rods bent? The pistons do look scuffed on one side.

 

[ericm979]

Hydrolocking doesn't happen all that often.

The right side piston shows the pin offset.

The left most piston skirt shows that piston was not getting enough oil. I can't tell if the right side piston skirt looks the same. That may not have been the only problem but it was a problem for sure. That's why there's aluminum on the bore.

On a plain bearing engine there is usually a lot oil flying around, plenty to lubricate the pistons on a low speed engine like this. Unlike the bearings it doesn't require a minimum oil pressure to lubricate the pistons, just some oil flowing. I'd look carefully for bearing damage and be sure to replace the pump. Maybe there's plugged oil passages too.

 

[clinter36]

Great point with the pistons. There were a couple versions of this engine and it appears that some versions had a cylinder projection above the block and some did not (mine is below the block). Maybe the same pistons were used and the recess is for valves on that other engine...? I really don't think this engine has been apart before, but its certainly a possibility. I will double/ triple check the piston orientation. It is noted in the manual, but I did not fully understand what they were referencing on the piston as I did not have one in hand at the time.

I did find it a little odd that the oil shaft was worn - probably by .030" on one side. That certainly would have allowed a gap in the pump area and must have had an effect on oil pressure.

 

[clinter36]

I attached piston installation pages from two manuals. It appears to me they are the correct orientation based on the sketch. I did not notice an arrow.

View attachment piston assembly.pdf

View attachment piston assembly 2.pdf

 

[ruffdog]

Muriatic acid does work for removing aluminum piston material from cast iron or steel. I have used it many times when a 2-cycle engine seized a piston. You can even buy it at hardware stores. Use a q-tip to dab on small areas if you want. If it is well within service limits, I would stay with the same bore size. It's just nice to keep the extra liner thickness for durability.

PS....just don't let the acid container leak on a concrete floor as it will eat it.......it is used as a floor cleaner though.

 

[denchen]

To final finish after reboring `years ago`, we used to wrap very fine emery paper around our sprung loaded honing bar. The paper was given a squirt of paraffin and turned slowly with an electric drill. Back then in the sixties, we would bore and finish to within a quarter of a thou of an inch. Just make sure everything is spotless and clean afterwards

 

[clinter36]

I ordered a 320 grit ball hone (brush research), we have a bunch of them at my work, but unfortunately we use coarse grit. I read that I should be shooting for 15-20 RA for the surface finish. The 320 should leave me with an RA 18 -30. I then read to finish that with a "nylon abrasive brush" to knock the peaks off the surface scratches and bring the RA down a little. But no one says what grit. Brush research has nylon abrasive brushes but it is only 320 grit. They also mention a nylon brush to clean cylinders in their guide (which is pretty cool BTW - http://www.brushresearch.com/pdf/FlexHone_Resource_Guide_For_Customer.pdf ) but I did not find the part number they recommend.

But anyway, I am going to give this a shot.

On another note, I just got a call from the shop who tested the injectors and they said one was completely clogged and the other 3 were marginal. add $500 for rebuilt injectors