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  #1  
Old 02-25-2008, 06:29 PM
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advice on 1972 250, bad cam

Hi, new to this forum and have been collecting M-B for about a year. I just purchased from second owner a '72 280 off CL for $200 and was going to scrap it. Advertised as not running, I did get it going to put on the trailer. It has a great interior, minimum rust, and the trans shifts fine. However there was a loud clicking from the engine.

Checking the valves, all but two were too tight, #4 exhaust has a worn cam lobe about 1/8" grove cut by rocker, #5 has a cracked E rocker. What little information I have on the car's past: about 200K miles on clock but odometer broken, rebuilt head and "new" carbs at 170K by original owner. Second owner totally neglected maintenance, therefore the valve issues. I set valves, now the car starts/runs excellent, no clicking, compression 145-150 all cylinders. But I'm not going to run it without deciding to:

1. Change 2 rockers and cam. Get this cam reground, or is it too far gone with 1/8" grove? Or where do I get a new/used good cam?

2. Replace engine with 300D from a parts car. The diesel runs excellent as does the trans., and has 150K. Would this diesel engine fit?? Part out the gas engine, at least the almost new carbs.

3. Or should I just strip and scrap the whole 250 like I originally intended?

Any advice???

thanks, Ron

PS My wife sort of likes this car and wants to drive it if not too much is involved for it to run. Our other M-B's are early 70's 220D diesels only one running presently, but not her cup of tea. Compared to the diesels, this thing can really move. But we are not driving it at present because I want to flush the engine to get out metal should the engine get a new cam.

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  #2  
Old 02-25-2008, 07:39 PM
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#4. Buy a replacement camshaft and replace it. Used ones are available from various people on forums. To replace the cam without pulling the head, the engine must come out because the cam can only be removed to the rear.
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Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

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  #3  
Old 02-25-2008, 10:20 PM
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Here's how I would assess your situation:
You paid $200 for the car, and although the cam sounds like it's worn badly it doesn't sound like a problem that would cause catastrophic failure anytime soon. Have the wife drive it for a month or two, see if she gets sick of it, then see if you want to replace that cam or not. FWIW, I had a cam problem on my 4.5 and drove with a VERY bad cam with horrible lobes for about 10k miles.
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  #4  
Old 02-25-2008, 11:32 PM
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That sounds like a good plan.

That car is pretty old and even with a new cam there will be plenty to fix on it on an ongoing basis. She may get pretty tired of it in a little while.

The repairs will get you upside down in a hurry so the only thing that makes sense is either to drive it only a little or fix it up well and keep it for a good long while to get your use out of it.

Tom W
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  #5  
Old 02-25-2008, 11:51 PM
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gimme a low-tech 240D
 
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Quote:
Originally Posted by wbain5280 View Post
To replace the cam without pulling the head, the engine must come out because the cam can only be removed to the rear.
Bain, are you sure about this?? Maybe cam w/stantions oughta be pulled by cracking the chain and pulling cam stantion headbolts but leaving the rest alone. Thats the procedure for pulling em on m180's. The idea is to keep each stantion matched to its camshaft bearing. Ye never wanna mix and match cams and stantions.

Otherwise, Toms 100% correct about worn camshaft lobes and/or rocker surfaces not bein instant death to the engine. Reconnoitre tougher starts, stalling if yer wife pumps the gas from standing start, slightly weaker engine performance - thats all.

Last edited by 300SDog; 02-26-2008 at 12:01 AM.
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  #6  
Old 02-25-2008, 11:56 PM
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Quote:
Originally Posted by 300SDog View Post
Bain, are you sure about this?? Maybe cam w/stantions oughta be pulled by cracking the chain and pulling cam stantion headbolts but leaving the rest alone. Thats the procedure for pulling em on m180's. The idea is to keep each stantion matched to its camshaft bearing. Ye never wanna mix and match cams and stantions.
This is how I've changed camshaft and towers. I've never pulled the head or an engine to do it. I never broke the chain though, just pulled the sprocket off the camshaft.
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  #7  
Old 02-26-2008, 01:10 AM
t walgamuth's Avatar
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I think I have done it this way too. Pull the sprocket forward, push the cam back and undo the bolts holding the tower on.

Tom W
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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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  #8  
Old 02-26-2008, 01:25 AM
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OK, well I never thought of that. Good plan.
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Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.
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  #9  
Old 02-26-2008, 03:53 PM
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Quote:
Originally Posted by Chas H View Post
This is how I've changed camshaft and towers. I've never pulled the head or an engine to do it. I never broke the chain though, just pulled the sprocket off the camshaft.
That is how it is done.
The trick is to do it on a cold engine and remove the coolant reservoir cap so there is no coolant system pressure b/c the tower bolts go through and are head bolts. Failure to do so can result in a leaking head gasket.
No engine pulling , but head sequence re-torque is required.
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  #10  
Old 02-26-2008, 08:03 PM
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Great idea, thanks

I really like idea of letting my wife have the car for a bit. First, I'll change the oil to remove any metal. The worn lobe has lost some metal, so I assume that's still in the engine, and new metal will be generated since the worn surface is not hardened. Is that correct?

Thank goodness I don't have to remove the head. But I still don't know where to get a good cam. Or should I try a regrind and (maybe) shim up that rocker? I see Mercedes had shims for it, I don't know if they would still sell them.

Thanks,
Ron
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  #11  
Old 02-26-2008, 08:53 PM
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Try these guys for the correct $800 cam for your $200 car:

http://www.mercedesengines.net/products.asp?cat=19

Last edited by JMela; 02-26-2008 at 09:01 PM.
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  #12  
Old 02-27-2008, 09:14 PM
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gimme a low-tech 240D
 
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Quote:
Originally Posted by Zeppo2K2 View Post
I still don't know where to get a good cam. Or should I try a regrind and (maybe) shim up that rocker?
Knowing MB ye can probly bolt cam & stantion towers combo straight across from any single cam 280, 250 or 230 engine of similar vintage. Oughta be no problem there, try posting a "wanna buy" thread at the parts forum. And pick up buncha replacement rockers too. You'd be outa yer mind stickin with them 2 crummy rockers you mentioned having in there now.

And based on what ye said, this motor sounds worth it. Never underestimate longevity of the Stuttgart engine block.

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