my cams all have off center points on the lobe, should I be worried - PeachParts Mercedes-Benz Forum

JB3 · #1 03-09-2010, 11:13 PM

this pic kind of shows it pretty well, the discolored area is a sharp point on the cam lobe. All of them have this, is it stock? or odd wear?

when running, there is a lot of top end noise from this motor. I don't think the valves have been adjusted within 100,000 miles, maybe not ever. this is an 85 617

vstech · #2 03-09-2010, 11:18 PM

... april is a few weeks away...

are you talking about the line on the tip of the lobe?

vstech · #3 03-09-2010, 11:22 PM

if the valves have not been adjusted, you could be looking at cam wear, but I would think the motor would burn the exhaust valves long before wearing out the cam...

JB3 · #4 03-09-2010, 11:27 PM

yeah, I know this seems like a ridiculous question, but im totally serious. You see on the second cam in the picture? there is a line where its picking up the light?

Instead of a standard smooth lobe surface, all of the lobes on my camshaft have a sharpish point right where that discoloration is, almost like the lobe is worn down off center, and has worn almost a corner into the lobe surface. My question is is that feature of the cam design, or wear?

the cams all look like they have wear, but not overly horrible. The motor has 260,000 on it.

There is a lot of rattle, metal slapping noise from the top end when this engine is running. Im wondering if I have cam wear, and maybe valve problems as well, I have not gone that far into it, I was adjusting the valves in order to do a compression test on this motor

jt20 · #5 03-09-2010, 11:43 PM

my personal theory on that, since you have the later code cam, is that this is caused by weak valve springs.

the only other way an impact could be created between the rocker arm and the cam is if the valves were religiously set too loose. Since the valves typically become tighter as they wear, it doesn't make much sense.

furthermore... if all the lobes display the same characteristics, the springs make the most logical sense.

"how bad is it"?? I can't really say. As long as the top of the cam profile has not been reduced, I would call it good to go.

leathermang · #6 03-10-2010, 01:01 AM

Some engines have that sort of thing to keep it from wearing a groove..
an offset to keep the surfaces moving in relation to each other..
The same theory upon which Valve Rotators are installed...

t walgamuth · #7 03-10-2010, 05:18 AM

I cannot see anything abnormal looking in the pic but there should not be any sharp edges in the cam profile. If there are I would think you need a new cam. Dirty oil could wear off the highest parts of the cam lobes. I probably would try to adjust the clearance and see what happens.

mplafleur · #8 03-10-2010, 06:54 AM

The cams lobes should be rounded and smooth. The FSM mentions that flat spots are an indication of cam wear. Flat spots will show up as a point, or line across the face of the cam.

I don't know however how flat an area should be before replacement is necessary.

layback40 · #9 03-10-2010, 08:25 AM

It doesnt look good. I have no experience with cam failure but it shouldnt look like that. Hopefully Roy will see your post & give his valued opinion.

vstech · #10 03-10-2010, 08:41 AM

are all the flat spots in the same location on the cam lobe? meaning, are all 10 lobes identical, or just the intakes, or what?

Alastair · #11 03-10-2010, 09:32 AM

Why not re-set the clearances correctly, and try again...

Cam looks fine from the pics I see....

The lobes are not exactly symetrical anyway--The way they are...

moon161 · #12 03-10-2010, 09:33 AM

Quote:

Originally Posted by mplafleur

The cams lobes should be rounded and smooth. The FSM mentions that flat spots are an indication of cam wear. Flat spots will show up as a point, or line across the face of the cam.

I don't know however how flat an area should be before replacement is necessary.

As the cam lobe wears, it will be unable to lift the valve fully. I think the FSM provides wear limits based on measuring the long dimension of the cam lobe. If the cam is surface hardened, wear will accelerate as the hard face is worn through. If the rest of your engine is happy, keep an eye out for a parts engine.

Skippy · #13 03-10-2010, 05:11 PM

I don't recall seeing a line like that worn into any cam I've ever seen, so I'm saying "not normal". I do think you should adjust the valves to spec, put it back together and see if you get good power, fuel economy, and driveability. If you do, I'd say just keep an eye on it every time you adjust the valves.

JB3 · #14 03-10-2010, 07:09 PM

Quote:

Originally Posted by vstech

are all the flat spots in the same location on the cam lobe? meaning, are all 10 lobes identical, or just the intakes, or what?

Its definitely on the first 6, I did not look closely at the last 4 as it was at that point that I leaned over far enough to accidentally drop my tool tray into my coolant collection pan.
But no, on the three cylinders exhaust and intake are showing the same wear pointyness.

Im waiting on a compression tester in the mail, but the engine has several other problems, and starts very poorly, and runs worse. The radiator was busted from an impact underneath, and I don't really know how long the PO may have run with that, or if he ever changed the oil.

There is no oil or coolant cross contamination, but there is HUGE corrosion in the cooling system, and a number of parts are so corroded and metal is breaking off as to need replacement. The water pump housing appears to be crumbling away from the inside.

I want to test the compression, do a leak down test, and if its unhappy maybe pull the motor, replace it and rebuild it. Even if its good, its leaking oil from so many places that I almost want to pull it anyway.

moon161 · #15 03-10-2010, 08:29 PM

If the engine has been neglected, a cam is not the only problem. Start shopping for a deerhunter.