Engine Overhaul Kama 554

[SPIKER]

3RRL looks like you are sure making some headway. glad it is coming to a head finally with the problems. Hows the Jinma running>?
Glad that there are people to keep good comments and records for others. I may have to do something someday similar to my Jinma but hope3fully not for several hundred more hours...

Mark

 

[3RRL]

Thanks guys, nice hearing from y'all.
Yes I've been very busy. Not just with the tractor tear down, but also splitting and stacking firewood for the Winter. Then there are the daily chores and other little projects that seem to pop up all the time.

I had time to upload these photos of the overhead valve spring compressor I bought at Harbor Freight. I was going to make one, but after seeing it there and for very little money, I thought I'd give it a try. After all, I'm by no means a mechanic so for this one time it seemed to fit the bill.



It was pretty easy to use.
The fingers are of unequal length. You insert them under the lowest spring coils and start turning the knob. Make sure the fingers remain under the coils and also make sure the compressors under the handle do not cover the little spring keepers. After you've turned it all the way down compressing the spring, the 2 little keeper halves can be removed from the retainer. I used a little magnet to get them out. Now you can take the spring off and release tension on the tool. Then flip the head over to slide the valves out.



You can see the exhaust valve is covered with carbon deposit.
But none of the valves were burned so I plan on reusing them. I marked each one and the head so I know where they go. After cleaning out as much crud and deposit as I could, I cleaned up the heads and got them ready to re-lap the valves for a better seat. I got one of those rubber suction cup tools to spin the valve into the seat. I plan on doing all of them that way.

 

[3RRL]

The Jinma is running great.
That's what we've been using for the little chores around the home. We're running the log splitter off it right now, but I've also used her tractor to smooth the road a couple times. I really miss the Kama though, especially for moving dirt for the pond project. Both bucket and box scraper are a lot larger on the Kama. Plus the power difference is hard to describe, but it is there, believe me. Both tractors have their strong points, but when it comes to moving and ripping dirt, it seems like the Kama does twice as much per pass as the Jinma. That's why I want to get it back in operation.
Of course the Jinma is Loretta's baby and the Kama is mine.

 

[3RRL]

My Diesel Engine Operation and Maintenance Manual says I need to have "Well lapped contact band both on valve and valve seat should be even, continuous and in grayish white color without pitting, scrape and brilliant line of 1.5~1.7mm width."
I think I have that now?



However, in checking the valve itself, it does not look like I have the same band with as on the valve seat. It does not seem to go around all the way either. Now I wonder how well they were lapped in the first place? My plan is to keep lapping until I establish that band width on both seat and valve. Then I can do the "kerosene test" to see if it leaks.

But before I continue lapping them, I have a couple questions.
My little manual says "The distance from the cylinder head bottom surface down to the valve head should be within 0.7~1.1mm."
1) I presume that means I can depth mic from the head surface down to the top of the valve, right? I haven't done this yet, but I will.
2) What happens if the valve sits down lower than the dimensions above?
3) What happens if the valve sits up higher than that dimension? I presume they could crash into the tops of the pistons, right?

Just eyeballing it, it appears to me that the old valves sit lower (into the head) than the dimensions, but like I said, I have not measured it yet. I want to know if they sit lower what damage that could do. I do have set of new valves which I also bought from Chip along with the rings last year. They sit up quite a bit more than the old valves. I'll measure those before lapping.

 

[3RRL]

But before I continue lapping them, I have a couple questions.
My little manual says "The distance from the cylinder head bottom surface down to the valve head should be within 0.7~1.1mm."
1) I presume that means I can depth mic from the head surface down to the top of the valve, right? I haven't done this yet, but I will.
2) What happens if the valve sits down lower than the dimensions above?
3) What happens if the valve sits up higher than that dimension? I presume they could crash into the tops of the pistons, right?

Just eyeballing it, it appears to me that the old valves sit lower (into the head) than the dimensions, but like I said, I have not measured it yet. I want to know if they sit lower what damage that could do. I do have set of new valves which I also bought from Chip along with the rings last year. They sit up quite a bit more than the old valves. I'll measure those before lapping.

OK, I just went out to measure the distance the valve sits below the head.
I'm assuming that's what #1 above means.
I measured the old valve and it sits down .064" (1.625mm) in the first photo.
I tried the new valve and it sits down .050" (1.27mm) second photo.



Sorry for the glare.
Both sit deeper into the head than the range given in the book. Does that mean I need new valve seats?
What happens if the valves sit too deep in the head? What is the outcome of that? Does it hurt or affect performance?

 

[Bob Rooks]

What happens if the valves sit too deep in the head? What is the outcome of that? Does it hurt or affect performance?

That will upset the relationship with the rocker arm geometry, although some of it may be compensated with the rocker adjustment when setting the valve lash. And you made the obvious true statement about a valve smacking a piston.

It appears that you've had a nice flame front on three of the cylinders, but the one on the end looks like an oil pump.

As far as lapping goes, on todays engines (applicable to Chinese too) the practice is to have the valve seat one degree more than the valve. This, in effect gives an "interference" type of fit under operating conditions, and actually extends the valve and seat life. Most automotive machine shops will concur. The lap band for that is about 1/32". Another reason the new valve is "higher" is because it hasn't been lapped to that particular seat. If you put a film of Prussian blue on the valve face and just touch it to the seat (do not turn it) you will see that it doesn't make concentric contact - even new valves have to be touched up.

The tolerances given for valve height is for when new seats are installed and also when the head surface is milled. They give a target range.

The reason the old valves sit lower in the head is because they are probably slightly concave - this is normal and will happen to all valves eventually through being slammed shut at 900+ degrees several times a second. What compounds this is that they are not two piece bi-metallic valves, and I doubt the seats are stellite either.

 

[IH3444]

Hello Rob,
Having been around engines, and rebuilt quite a few, all you have to do is get the overall vavle length measurement, and then grind the valve stem end a few thousands. There is a specific machine for this, but a high quality grinding wheel, whith a good V groove steady rest will work. It's very simple, and this is how the valve length is adjusted when the valve seats are refaced. Your valve seats are fine I'm almost sure due to the low hours. Just need to shorten the valve stems a little bit. Very easy task for sure an experienced senior mold maker machinist as yourself. IH3444

Sitting that small amount in the head deeper is not a problem, it is very slight.

If the new valves aren't touching all around the seat, or are uneven in the lapping band, you may want to check your valve guides for wear, or uneven wear, and possibly replace them, then have the seats refaced. One quick way to check this is to install one of the new valves, insert all the way until it almost contacts the seat, then gently rock it. It should have almost no play. Do the rocking in the direction that the rocker arm presses down on the valve. This is where the most wear will occur, and where the checking should be done.

There should be a spec for this in the manual, and you can go to a set up with a dial indicator if you like. Being very experienced with this check, I've learned that there should be almost no play, and the valve should glide very smooth in the guide.

Most guides are cast steel, but some are silicone-bronze. The old ones can be pressed out, and new ones pressed in.

The rocker arm geomerty will mostly be unaffected due to the fact of the very mild lift and durations of these slow speed diesel engine camshaft profiles. If you get the guides checked, the stems ground to proper length, and the seats refaced I doubt you will be out of spec. with the rocker arm geomerty. If you are, and it's measurably out of tolerance, then a small shim under the rocker arm will most likely put you right back into the ball park. Of all the engines I have remanufactured, from lawnmowers, to Porsche 911 6 cylinders, to detroit V8's, I've only had to shim the rockers on 2 engines with the method described above.Good luck, and I wish I was there to help you. Remanufacturing an engine to new specs, and starting it up is a great feeling. Your'll will run better than new after this. You'll see.

 

[bjr]

Yeah, what I'm reading here is: "take the head to a good auto machine shop for proper valve grinding" and I agree. I'm no stranger to engine rebuilds and I use a good auto machine shop for this especially. bjr

 

[SPIKER]

Yeah, what I'm reading here is: "take the head to a good auto machine shop for proper valve grinding" and I agree. I'm no stranger to engine rebuilds and I use a good auto machine shop for this especially. bjr

If you do decide to take the head in to a shop I would make sure to give them as many specs as you can for them, they will need to know what the specs are for this head.. While they are pretty much all same setup, each block/head/valve has it's own specifications that need to be maintained. if the valve is setting too far down (recessed) it can effect the combustion ignition timing as there will be slightly LESS compression in that cylinder, while it should still ignite there may be a performance decrease. conversely is true if the valve sticks out to far anything from contact of piston to pre-ignition/detonation can occur. I too have done my fair share of engine work but still take my heads to a shop as I have a grade school buddy who does on the side machining work (actually full time form his house/shop/barn...)
I get charged the same but get better care and better work than what most head shops would do... hope you marked valves for Pos, cylinder ect...

Mark

 

[3RRL]

Wow, thanks guys for taking the time to give me such detailed information!
Of course I have several questions and would appreciate your input. In my field of expertise, I know sometimes you have to live with imperfection. But I know the limits and what I can get away with if I have to. I also know where to draw the line and make it "perfect" because sometimes that's the only acceptable thing to do. Probably much like you guys when you see the engine torn apart. You know exactly what to do and what "will" work and what "won't" work and where to draw the line.
But not knowing about this stuff, I need to rely on you guys to tell me what is "OK" and what is absolutely "Not OK". You know what I mean? The information that Bob, IH3444, bjr and Spiker gave about the valves sitting deeper for example, is OK and I will just lose a little compression and to adjust the rocker arm geometry.
Although not out of the question, I am trying to avoid taking the head in. If I can get it back in acceptable shape, even though not 100% perfect like described above, I would rather do it myself. I just moved up to this town and don't know any body's reputation here. It would be a crap shoot. Plus, being a Chinese engine, I'm not even sure if I have all the specs to follow.

First, I am particularly interested what Bob said here:

It appears that you've had a nice flame front on three of the cylinders, but the one on the end looks like an oil pump.

Does "nice flame front" mean it is a good thing? Is that what you want to see? (You can see how experienced I am at these things)
Note that I found on that last cylinder, that the connecting rod journal bearing was partly "squished". Perhaps that had something to do with that cylinder looking like it did? While working the tractor for the last time, I thought I heard a "knock". I saw the oil pressure start to drop and drove it immediately into the barn and shut it down. Right then was when I decided to tear it apart. After seeing the bearing, now I believe that is what I might have heard and that is what caused the low oil pressure. I called Chip and he is the one who told me that is a sure sign of oil pressure loss and that the pump is probably still OK.
I bought all new journal bearings from Chip and will install them. The crankshaft journals are OK, even that last one. There is no galling and they are clean and bright.

Second of particular interest are a number of things IH3444 said here:

Hello Rob,
... all you have to do is get the overall valve length measurement, and then grind the valve stem end a few thousands.
... Your valve seats are fine I'm almost sure due to the low hours. Just need to shorten the valve stems a little bit.
... Sitting that small amount in the head deeper is not a problem, it is very slight.
... you may want to check your valve guides for wear
... Do the rocking in the direction that the rocker arm presses down on the valve.
... there should be almost no play, and the valve should glide very smooth in the guide.
...The rocker arm geometry will mostly be unaffected due to the fact of the very mild lift and durations of these slow speed diesel engine camshaft profiles.
...If you are, and it's measurably out of tolerance, then a small shim under the rocker arm will most likely put you right back into the ball park.

A lot of information!
What I'm getting from this clipped quote is that the valves sitting slightly deeper will not necessarily hurt (except slight compression loss as both you guys said) and that I can grind the end of the valve to get the rocker arm geometry back to spec. I will also check the valve guides in the manner you suggested.

Assuming I lap all the valves so the all seat properly, I could then measure each one to see how much deeper it sits than spec, and grind off the end of each valve stem that amount respectively, right?
In other words, after lapping I measure the valve depth and it is, say .020" too deep. Then I would grind off .020" off the end of the valve stem, right? That would put the rocker arm geometry back into spec, right?
If so, I can certainly do that easily in my shop.
Thank you all so much for this valuable information!