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Lost a cylinder in DT-407, found this..........


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I was grind feed as I normally do last week, kids are back in school so I was by myself.  Had the DT-407 just screaming as I normally do, and I could keep up shoveling by myself which I found odd, didn't hear anythng out of the normal.  Had about 500 lbs left, heard a weird noise, and the smoke started.  I thought it was an injector, so let it idle a bit, unhooked it and shut it down.  We got my brothers 826 to finish and unload it.  Anyhow, pulled the injector yesterday on #6 and it was fine.  Figured we had other issues so me and the boy pulled off the fuel tank and pulled the valve cover.  Found this

1048415675_DT407Rocker.jpg.2b7af30511607669f58d69291fb0e7cb.jpg

Question I have is it fatigue or do I have a guide that worked loose?    I seem to remember laying acouple welds on these rockers 10+ years ago for some reason, but don't recall now why.  Are these available new yet?  I did a search and didn't find much, but haven't looked at mother fiat either.  Maybe that was why we laid down welds as we couldn't get them back then?  

 

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22 minutes ago, TP from Central PA said:

I was grind feed as I normally do last week, kids are back in school so I was by myself.  Had the DT-407 just screaming as I normally do, and I could keep up shoveling by myself which I found odd, didn't hear anythng out of the normal.  Had about 500 lbs left, heard a weird noise, and the smoke started.  I thought it was an injector, so let it idle a bit, unhooked it and shut it down.  We got my brothers 826 to finish and unload it.  Anyhow, pulled the injector yesterday on #6 and it was fine.  Figured we had other issues so me and the boy pulled off the fuel tank and pulled the valve cover.  Found this

1048415675_DT407Rocker.jpg.2b7af30511607669f58d69291fb0e7cb.jpg

Question I have is it fatigue or do I have a guide that worked loose?    I seem to remember laying acouple welds on these rockers 10+ years ago for some reason, but don't recall now why.  Are these available new yet?  I did a search and didn't find much, but haven't looked at mother fiat either.  Maybe that was why we laid down welds as we couldn't get them back then?  

 

i am really puzzled as to why u have weld on the rockers and it looks like they are welded to the shaft, buy it makes no sense. and what exactly are u referring to? those rockers sure dont look to be sitting right as hard to tell with the picture.

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Just now, rustred said:

i am really puzzled as to why u have weld on the rockers and it looks like they are welded to the shaft, buy it makes no sense. and what exactly are u referring to? those rockers sure dont look to be sitting right as hard to tell with the picture.

The weld isn't to the shaft, the rocker to the pivot tubes which slide over the shaft(#9).  Maybe those were spinning in the stamping?  I wish I could remember, but it has ran this way now for over a decade. The last one(#6E) is broke on the push rod side and just happened.  Curious if this is a known weak spot or I got a valve guide working loose and that is the fail point.  I would have the thought the push rod would bent before the rocker would break in that case.  I wish I was like Dale and could draw sweet lines and stuff to what I am trying to point out.  Now that I looked at Messicks, I think we patched it because we needed it at the time and had to buy the complete assembly which would have been to far out.  I guess 10 years isn't bad for a "Patch".

image.png.f6b52f45dc8a230c4938e982f01baef8.png

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2 minutes ago, jeeper61 said:

Is the push rod bent or did the rocker fail?

 

Rocker Failed for sure, if you look close at the last one its broke at the pivot.  Didn't tear it apart anymore to find out if the push rod bent as well.  Trying to limit work on it, as the weather is too nice at the moment, have other stuff more important before winter.

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I hear ya

Have to do a head gasket but there is painting to be done before it gets to cold.

After you get the rocker shaft it should be pretty easy to tell if the guide is bad.

 I would expect the wear pattern on the valve tip to be funky if the guide is gone 

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2 minutes ago, jeeper61 said:

I hear ya

Have to do a head gasket but there is painting to be done before it gets to cold.

After you get the rocker shaft it should be pretty easy to tell if the guide is bad.

 I would expect the wear pattern on the valve tip to be funky if the guide is gone 

I know they have been a issue, but didn't know how common of an issue it is.  Seem to recall, might have been Diesel Doctor tearing off the valve cover a few times before he found it on one of these.  

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You had a valve guide work up in the head until it put the valve into a bind.

Something had to give and in this case, it was the rocker.

Look thru the valve spring and see if that guide is setting higher than the others.

Check the push rod too for straight as that was really stressed.

This always happens on #6. Probably due to additional heat.

You can replace the rocker with a new or used one and take a chance of it happening again.

I would not try and weld it again.

You should pull the head and have all guides looked at and fixed.

Your call on that one.

 

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4 minutes ago, Diesel Doctor said:

You had a valve guide work up until it put the valve into a bind.

Something had to give and in this case, it was the rocker.

Look thru the valve spring and see if that guide is setting higher than the others.

Check the push rod too for straight as that was really stressed.

This always happens on #6. Probably due to additional heat.

You can replace the rocker with a new or used one and take a chance of it happening again.

I would not try and weld it again.

You should pull the head and have all guides looked at and fixed.

Your call on that one.

 

Yeah, know how that goes..............Would like to pull the engine and do everything at once, with the election out-come I am not sure I want to throw money out there right now if I can help it.  But on the flip side of that, I'd sure miss my feed grinding tractor.  Will take a closer look once I tear it apart some more, glad you chimmed in.  Thanks

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Had a few minutes tonight, pulled that end rocker off(Easy enough) to have a look see quick.  Appears it might have had a old break and if finally gave up.  I remembered that the round part with the bushing was spinning in the stamping years ago.  We were worried the oil hole would not do much use like that so we spot welded them to keep that located right.  I put my dial indicator on it quick and had .483" from closed until it bottomed out on that valve.  My brother has my books, but what is the spec for them opening?  Didn't have any more time, to look at others to see if they were consistant.  Push rod on my layout surface plate(Which should be flat withing a few .0001") looked great, so that wasn't bent.  

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Looks like a very similar story to the rocker trouble I had on my 856. Exhaust rocker broke on #6. Turned out that was the rocker that I knew was loose on the bushing last time I was in the head. I just didn’t weld it like you did. I had to run the tractor with that broken Ex rocker for an hour or so before I could fix it, by the end of that time the In rocker had failed also from opening against all that excess cylinder pressure. Two good used rockers and all is good again. These tractors are 50 years old, things happen. I found a complete rocker assembly at Rock Valley Tractor parts for $200. 

E0496AF4-B082-444B-AFA5-C7AEDF1044C5.jpeg

81821B0D-D192-4666-ACA9-B1C27385010C.jpeg

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I would find a new or good used rocker and put it back together.

If you got ten years out of the last fix, and you get five out of this one, you win.

If you ever pull the head, you can then look at the guides.

PS:

I believe there is  a difference in metals from the guides and the cast head.

I think the head expands more than the guide, the guide gets loose, works it's way up until it binds the valve and something breaks.

Why this always seems to happen on #6 exhaust.

When the valve stops moving, the engine vibration and gravity moves the guide down where it belongs.

When the engine cools off, it holds the guide somewhat solid.

My thoughts on what happens and why?

 

 

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22 hours ago, TP from Central PA said:

Yeah, know how that goes..............Would like to pull the engine and do everything at once, with the election out-come I am not sure I want to throw money out there right now if I can help it.  But on the flip side of that, I'd sure miss my feed grinding tractor.  Will take a closer look once I tear it apart some more, glad you chimmed in.  Thanks

Don't want to de-rail the thread, but the election outcome's not a done deal yet.

Carry on.

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Just now, TP from Central PA said:

Yes, I know, but you have to back off from what would of been full tilt to a half ahead out of caution.

Agreed. Not a good time to be making major financial decisions.

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30 minutes ago, Diesel Doctor said:

I would find a new or good used rocker and put it back together.

If you got ten years out of the last fix, and you get five out of this one, you win.

If you ever pull the head, you can then look at the guides.

PS:

I believe there is  a difference in metals from the guides and the cast head.

I think the head expands more than the guide, the guide gets loose, works it's way up until it binds the valve and something breaks.

Why this always seems to happen on #6 exhaust.

When the valve stops moving, the engine vibration and gravity moves the guide down where it belongs.

When the engine cools off, it holds the guide somewhat solid.

My thoughts on what happens and why?

 

 

I am sure there is material differences obviously or the guides wouldn't be replaceable.............And the co-efficient of expansion between the guide material and the cast head I am sure are different, but with that said I am not sure they would work loose enough to fail easily by gravity back to "Home Position", which is why I measured it, going to compare it to the rest and see.  I know when we did interference fits in the machine shop, one part cold and one part hot they fell together, but with both head and guide at the same temp, I can see parts working loose but not falling apart or back together by gravity. If anything I would almost expect once it worked out, the stem sticking up would be cooler towards the top and it would stick out and stay there?  Now the question I have is Doc, have you had similar issues with the flat stamping and the round part seperating themselves?  I must not have been the only one if Gearclash had a similar issue?  Are the new ones built the exact same as the originals?

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8 minutes ago, Steve C. said:

Agreed. Not a good time to be making major financial decisions.

Problem I have is the engine runs awesome otherwise, would prefer to wear it out some before I full tool chest into it.  I don't put a ton of hours on it, but I do use it........Although I said that too about the 2+2 and I thought we hardly used it, but put 75 hrs on it with just a tub grinder this year and I know this one runs alot more than that one does.  My tach hour meter doesn't work, but the rpms do, haven't had a chance to send it out.  

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I remember another topic in the past couple months of same thing with 3 different styles rockers and talking which was the strongest don’t know if that’s an option for this engine 

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23 hours ago, TP from Central PA said:

Yeah, know how that goes..............Would like to pull the engine and do everything at once, with the election out-come I am not sure I want to throw money out there right now if I can help it.  But on the flip side of that, I'd sure miss my feed grinding tractor.  Will take a closer look once I tear it apart some more, glad you chimmed in.  Thanks

 

IMG951592.jpg

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1 hour ago, 1466fan said:

 

IMG951592.jpg

I believe I'll share that.

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Sons 1456 broke one rocker last winter, we replaced with a good used one and has worked fine since, but just last week noticed that the belt pulley part of the damper is loose and wobbling. I'm sure we checked that at the time of rocker replacement, but dont remember for sure. Its sidelined until seal gets here later this week, got a new damper here already. Better take a look at your pulleys too

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5 minutes ago, 1958560 said:

Sons 1456 broke one rocker last winter, we replaced with a good used one and has worked fine since, but just last week noticed that the belt pulley part of the damper is loose and wobbling. I'm sure we checked that at the time of rocker replacement, but dont remember for sure. Its sidelined until seal gets here later this week, got a new damper here already. Better take a look at your pulleys too

Yes, I may just replace that anyhow.  I never replaced it.

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Put it back together today, plenty of travel left after the rockers on #6 both intake and exhaust are open, so I will see how it works out.  Front pulley rubber looks good, everything up there is tight...................For the time being we are going to just run it.  Had it running and it sounds good, will put the hoods back on it tomorrow and wash it............Back on the feed grinder it will go.

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