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I met a guy today - who said something about his car needing valve job, because when the engine is hot - they "are not closed all the way" and the car stalls and it is hard to start. This pertained to 420 SEL 1987.

My first impression was - B/S - but then I remembered some engines having problems with valves because of other type of fuel. (LPG, CNG - so called "dry fuel") I saw these valves literaly being eaten and the clearances were such, that valves could not close when hot.

Now my question - is it happening on 420 SEL????
Is this possible?
What are the typical valve problems in high mileage 420 engine?
 

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danwatt - 5/9/2005 2:18 AM

You have hydraulic lifters. Can't really adjust them. You can change the valve guides, seals, etc. Can't hurt.
You have hydraulic compensators and shim pucks. You either measure the valve stem height or use the special tool from Mercedes and then adjust the shim pucks to get back to nominal. V8s tend to wear looser - ever hear the noise? The confusion may be from diesels that can be VERY hard to start cold with valve clearance too tight due to wear.
High mileage V8s will have worn guides - they all do it. The guides will go long before a valve seat fails. And after you get a valve job it won't last as long as the factory unless they have the same jigs.
 

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NordRhein - 5/9/2005 8:36 AM

And after you get a valve job it won't last as long as the factory unless they have the same jigs.
I beg to differ.. My machinest in NY has been seeing as many miles as the factory fresh heads.
He has been doing this (95% MB) for 30 years..All the Major dealers (MB of NYC, Ralleye Motors etc, etc..) all use him for their machining. I trust his work enough to send my heads from here in Atlanta to him..:)

Jonathan
 

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Discussion Starter #6
NordRhein - 5/9/2005 8:36 AM

danwatt - 5/9/2005 2:18 AM

You have hydraulic lifters. Can't really adjust them. You can change the valve guides, seals, etc. Can't hurt.
You have hydraulic compensators and shim pucks. You either measure the valve stem height or use the special tool from Mercedes and then adjust the shim pucks to get back to nominal. V8s tend to wear looser - ever hear the noise? The confusion may be from diesels that can be VERY hard to start cold with valve clearance too tight due to wear.
High mileage V8s will have worn guides - they all do it. The guides will go long before a valve seat fails. And after you get a valve job it won't last as long as the factory unless they have the same jigs.



I get the point. Valve seats do not wear out fast.
This means the man was full of B/S and he had major problem with his emissions systems.

OK. Thank you for your time and all the responses.
I appreciate it.

Good luck guys!
 
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