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  #1  
Old 05-13-2012, 08:47 AM
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617 Head Gasket Replacement

I have a few questions about replacing the head gasket on my 1983 300TD:
1. I have reviewed both the FSM and Haynes and neither says much about how to handle the cam chain other than painting a mark on the chain and sprocket before removing the sprocket--and Haynes says to maintain tension in the chain. It appears that the chain cannot slip on the injection pump timing device so long as the retaining bolt is not removed from the side of the crankcase. How much do I need to worry about it slipping on the crankshaft sprocket? Any tricks to handling the chain while removing the head?
2. I am planning on reusing the head bolts so long as they meet the length requirements in the FSM. Any thoughts pro or con on this?
3. It is tempting to replace the valve seals while the head is on the bench, but I really do not have much oil consumption(180,000 miles on the car) --should I leave them alone?
4. Any other advice is welcome.
Peter Ferguson
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Old 05-13-2012, 09:44 AM
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Quote:
How much do I need to worry about it slipping on the crankshaft sprocket?
There is a tab on the underside of the crank pulley that will prevent it from losing orientation. Just tie the chain off where it does not fall too far down into the opening and you should be fine. As already stated make sure you mark the chain/cam sprocket with paint (that will not wipe off).

As long as the head bolts are within spec you should be fine.

If money is tight I'd leave the valve/valve seats alone.

Make sure someone is there to help you when you lift the head off.
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  #3  
Old 05-13-2012, 10:41 AM
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Can you give us the symptoms of the head gasket failure which necessitates replacement. There are questions on here now and again about whether a head gasket is bad and they fail so infrequently on the 617 that there aren't a lot of threads with diagnostic info.
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1984 300SD 315k--daughter's car
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Old 05-13-2012, 11:29 AM
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Quote:
Originally Posted by 83TD View Post
1. I have reviewed both the FSM and Haynes and neither says much about how to handle the cam chain other than painting a mark on the chain and sprocket before removing the sprocket--and Haynes says to maintain tension in the chain. It appears that the chain cannot slip on the injection pump timing device so long as the retaining bolt is not removed from the side of the crankcase. How much do I need to worry about it slipping on the crankshaft sprocket? Any tricks to handling the chain while removing the head?

3. It is tempting to replace the valve seals while the head is on the bench, but I really do not have much oil consumption(180,000 miles on the car) --should I leave them alone?

1. When I did the head on the SD, I took great pains to suspend the chain sprocket and keep upward tension during the entire R & R process. This is no easy task and requires some suspension from above. It also requires some manipulation to get the head off the suspended sprocket and chain. After completion, I found some posts on here that confirm that the opposite situation is actually the case. You can drop the chain down into the abyss and fish it out later and the job will still work perfectly, provided that you have marked the chain and the cam sprocket for alignment. Live and learn.

3. It's such an extensive job that I cannot see the shortsightedness of not reworking the head at 180K. I spent $600 or so on the SD and did exhaust valves, guides, prechambers and seals and I have absolutely no regrets. The engine starts effortless at zero degrees and it is currently achieving 30 mpg with conservative driving habits. If you're going the distance with the vehicle, the additional cost is minimal when calculated on a per mile basis. The satisfaction is priceless.
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Old 05-13-2012, 11:53 AM
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When I pulled my head/ IP I set the timing by the reference marks on the crank and the cam. You will have to pull the IP if you go this route, however.

Definitely replace the valve guide seals.

When the head is out measure your valves and valve guides. @ 220k my exhaust valve guides were out of spec, even though the engine ran/ started fine.

While the head is out, I'd lightly port it as well. Even if it only makes a small difference, it will make you smile knowing everything is at it's best when you start it back up
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  #6  
Old 05-13-2012, 02:08 PM
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If you get in a panic about the position of the camshaft and the crankshaft and you think you've skipped teeth / got the timing 180 degrees out / bound to be having pistons hitting valves...

...DON'T PANIC!...

Just remove the rocker arms from the head.

You can then turn the crank to your heart's content the camshaft will spin BUT the valves won't open and the terrible will NOT happen.
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Old 05-13-2012, 03:45 PM
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Quote:
Originally Posted by engatwork View Post
There is a tab on the underside of the crank pulley that will prevent it from losing orientation. Just tie the chain off where it does not fall too far down into the opening and you should be fine. As already stated make sure you mark the chain/cam sprocket with paint (that will not wipe off).

As long as the head bolts are within spec you should be fine.

If money is tight I'd leave the valve/valve seats alone.

Make sure someone is there to help you when you lift the head off.
You wouldn't advise lapping the valves, or would that just mean replacing parts like seals and those roller gizmos, that were probably OK?
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  #8  
Old 05-13-2012, 06:19 PM
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You know, now that I have put some more thought into it I believe I probably would have the head gone through at a reputable machine shop seeing as how it is a 617 engine. On my dd (606 engine) at a little over 250k miles I installed a new head gasket and did not do anything to the head and the car runs out fine.
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  #9  
Old 05-13-2012, 06:22 PM
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I am replacing the head gasket due to an oil leak at the rear passenger side corner of the gasket that seems to be getting worse. I have been trying to find another source for the leak, such as the valve cover gasket or a pinhole leak in the turbocharger oil line, but it seems to be coming from the head gasket. Believe me, it pains me to have to do it at this time--I am the original owner of the car and have done my best to take good care of it over the years; i.e., no winter driving. It still starts and runs flawlessly and we just got back from a road trip to Montana, averaging 25 mpg at 75mph speeds. Thanks to all for the helpful advice.
Peter
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