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  #1  
Old 05-12-2019, 08:22 PM
Joe
 
Join Date: May 2019
Location: Connecticut
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W123 Cam Setup, Rebuilding Cylinder Head

Hi...as I'm preparing to pull my 300D's cylinder head, I'm having trouble finding a new cam to instal as opposed to using the old one...are these available anywhere? If not available, then who regrinds old cams and what is the cost? Also, when removing and reinstalling the cam supports and adding new bushings, do people just pop in the cam or send the cam and head, with supports, to a shop to have them align bored and polished? Do rockers need any special treatment before being reused? Appreciate any input from other members...many thanks!
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  #2  
Old 05-12-2019, 11:42 PM
t walgamuth's Avatar
dieselarchitect
 
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How Do you know you need to replace it?
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..I also have a 427 Cobra replica with an aluminum chassis.
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  #3  
Old 05-13-2019, 12:43 AM
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If you line bored the Camshaft Towers the bearing bores would then be oversized and you would need a camshaft with oversized bearing journals. And I have never read of anyone saying there is such a thing.

Member DeliveryValve mentioned a place that re-ground camshafts but since this is an old vehicle that not many of were sold compared to any single model of say a chevy I doubt if many places regrind them.

I am not sure what info is available in the Factory Service Manual concerning the lift of the cam lobes and so on that some one who grinds cams could use for info if they had not.

New good ones show up on eBay. But, you need to be sure what you are buying.
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  #4  
Old 05-13-2019, 01:04 AM
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I was under the impression that you don't really need to mess with the cams on these unless there is an obvious failure. I'm having mine polished at my local machine shop, since had been out in the elements for a while. I do have a tiny bit of surface rust on some of the lobes, but very light. No real damage to it.
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  #5  
Old 05-13-2019, 03:03 AM
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In case of swap one needs to verify the compatibility of cam and rocker arms(and valve nuts in some cases). Different metallurgy introduced at some point(late 70-ies was it?)...or just swap the setup as a whole.
What is the matter with the original one?
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  #6  
Old 05-13-2019, 04:25 AM
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The camshafts are identified at the far end with numbers - these numbers are referenced in the FSM

Oversized variations are meant to exist but I've not seen them for sale before - perhaps Mercedes has a pile of them somewhere (!)

The book (FSM) says to change the camshaft and rocker arms as a set

There is a difference between the non turbo and turbo OM617 camshafts - the turbo has higher lift - there's also a difference between the early and late non turbo OM617 camshafts - the non turbo got more of the turbo "tweaks" (Sorry I can't remember exactly what all the tweaks were - there's an OM617 development publication out there floating about in what bell ends now refer to as the cloud which is real anorak reading material)

The most wear at the top end of the OM617 is usually in the spindles for the rocker arms - these longitudinal spindles often have nasty gouges / wear marks but they are fairly cheap to replace.

##########

As asked and mentioned already => Why do you need to replace what you've already got?

If you are falling into the trap of thinking "new is better than old" - STOP - think again!
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1992 W201 190E 1.8 171,000 km - Daily driver
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  #7  
Old 05-13-2019, 10:20 AM
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Quote:
Originally Posted by Stretch View Post
The camshafts are identified at the far end with numbers - these numbers are referenced in the FSM

Oversized variations are meant to exist but I've not seen them for sale before - perhaps Mercedes has a pile of them somewhere (!)

The book (FSM) says to change the camshaft and rocker arms as a set

There is a difference between the non turbo and turbo OM617 camshafts - the turbo has higher lift - there's also a difference between the early and late non turbo OM617 camshafts - the non turbo got more of the turbo "tweaks" (Sorry I can't remember exactly what all the tweaks were - there's an OM617 development publication out there floating about in what bell ends now refer to as the cloud which is real anorak reading material)

The most wear at the top end of the OM617 is usually in the spindles for the rocker arms - these longitudinal spindles often have nasty gouges / wear marks but they are fairly cheap to replace.

##########

As asked and mentioned already => Why do you need to replace what you've already got?

If you are falling into the trap of thinking "new is better than old" - STOP - think again!
Can't remember the details but there is a difference in the hardening of the Camshafts and the pads on rocker arms in the later models.

People with experience rebuilding Gasoline Engines especially from US Cars are used to the availability of an extensive number of parts for rebuilding as well as an industry that regrinds crankshafts, Camshafts and can supply oversized and undersized bearings. Somewhat the same with US made Diesel Truck Engines.
So you have a mindset on what you can put into an engine or reuse and still consider to be a rebuilt Engine.
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  #8  
Old 05-13-2019, 11:24 AM
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Quote:
Originally Posted by Diesel911 View Post
Can't remember the details but there is a difference in the hardening of the Camshafts and the pads on rocker arms in the later models.

People with experience rebuilding Gasoline Engines especially from US Cars are used to the availability of an extensive number of parts for rebuilding as well as an industry that regrinds crankshafts, Camshafts and can supply oversized and undersized bearings. Somewhat the same with US made Diesel Truck Engines.
So you have a mindset on what you can put into an engine or reuse and still consider to be a rebuilt Engine.
Oh yeah there's a mention in the FSM about not dropping the cast (iron?) camshafts isn't there? I should really RTFM but I can't be arsed...


...I'm not doing the job! I'm just sat in me armchair...
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!
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  #9  
Old 05-13-2019, 11:17 PM
Joe
 
Join Date: May 2019
Location: Connecticut
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SO guys, I'm confused...do most people doing a rebuild just polish the cam and re-use it with the bushings as-is? And if so, do you place the cam towers back on the new head loose, insert the cam, then tighten down so all is aligned right? I wanted to get a new cam and bushings just to have everything good to go...I remember having a 300SE with an M103 engine that had a cam that wasn't hardened right by the vendor...MB had a recall when new as I recall...cam wore quickly on a couple of lobes and ticked like mad...I didn't want that to happen here if I switch for another cam that is not new...
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  #10  
Old 05-13-2019, 11:23 PM
t walgamuth's Avatar
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The cams are usually in good shape and are reused. Have your machinist look at it.
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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  #11  
Old 05-14-2019, 12:02 AM
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The M103's are well known to have issues with cam wear. The diesels not so much. Supposedly the early 617 turbos in the W116 had hardness issues, but the ones used in the 123's and 126's didn't. Unless you've had oiling issues or have excessive scoring, you're probably fine.
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  #12  
Old 05-14-2019, 12:31 AM
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Quote:
Originally Posted by Stretch View Post
Oh yeah there's a mention in the FSM about not dropping the cast (iron?) camshafts isn't there? I should really RTFM but I can't be arsed...


...I'm not doing the job! I'm just sat in me armchair...
You have more experience with the Mercedes stuff then I do. I have had to do very little to the Engine beyond maintenance.

When I got the CD Factory Service Manual I sort of glanced over stuff. Don't remember the details. But, I saw enough to know that if I was going to replace a camshaft or rocker arms I should go back read it again.

But, I am getting the impression the guy that started this thread had not read the Factory Service Manual on rebuilding the cylinder head and he might not have the equipment to measure the inside and or outside of bearing journals.
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  #13  
Old 05-14-2019, 06:01 AM
t walgamuth's Avatar
dieselarchitect
 
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The machinist can look at the cam and tell if it is worn. Then if it is worn might measure it.
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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  #14  
Old 05-14-2019, 08:14 AM
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Mercedes had a hardness issue at one time. It did not impact the 123 diesels to the best of my knowledge. For some reason years ago the amount of hardness deteriorated towards the front end of the cams.

Other than checking the Cam bearing clearance they should be good to go usually. Unless perhaps the engine has a massive amount of miles on it.

Just remember to number the cam followers. Can wear has not been a real issue with these engines. Even at fairly high accumulated milage. A visual inspection of the lobes journals and followers should be enough in the vast majority of cases.
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