what could have broken the cam on my 240? - PeachParts Mercedes-Benz Forum

vstech · #1 04-16-2010, 08:52 AM

OK, I've started tearing into my 240D 5Speed Euro, and I'm confused...
I figured the only thing that could have broken the cam was valve/piston contact caused by a jumped tooth on the TC,
so I lined up the timing marks on the cam to see where the timing marks line up on the balancer... 0 ... so, um, what broke the cam?
I measured the height of all the spring retainers, and they all line up within a few thousandths so no overly bent valves.
the front tower is split on the passenger side of the block so, it's possible a bind in the cam bearing caused the chain to pull the tower over, twisting the cam and shattering it, but I don't know.
I'm pulling a new cam from a donor car, and I'm going to install it and see what compression is on the motor.
are there any differences in cam tower/camshaft between an 84 240 and a 78 that would cause problems with this swap?

junqueyardjim · #2 04-16-2010, 10:38 AM

On the 240D with broken cam that I got out of Florida, (read more about this car on post of Nathan Carter), I thought the cam broke because of the missing small head bolts at the front of the engine. Three of the four were not installed after a rebuild of head and engine. However, when I was going to put the head back on a week ago, in pulling the chain through the head on the drivers side, it snapped and I had about 14" of chain in hand. Now Nathan had told me the engine was locked up. But after having it shipped up the engine seemed free when we checked it after removing the head, at least as far as we could move it with the chain cut. But now when that chain came loose, we could immediately see "trash" down in the cavity below the injection pump sprocket. And what the cause of that was the fact that the vacuum pump had lost a large part of the washer that the spring rests on. Roughly half of that washer broke out and fell into the chain and jammed it all up at the bottom sprocket, streched the chain and broke it on the sprocket. Fortunately no damage other then the chain, the cam shaft and the long chain rail at the bottom of the engine. Oh yes, plus the vacuum pump. I think it really pays to occasionally take a good look at the internals of that vp.

Johnt49 · #3 04-16-2010, 11:06 AM

Quote:

Originally Posted by vstech

are there any differences in cam tower/camshaft between an 84 240 and a 78 that would cause problems with this swap?

No problem as long as you use the towers that come with the newer cam. They have larger journals than the 78. The newer cam also has slightly different timing/lift specs, but works fine. Be sure to use the cam followers in the same order from the new cam as well. Mismatched used parts can destroy each other in very short order.

vstech · #4 04-16-2010, 11:38 AM

Quote:

Originally Posted by Johnt49

No problem as long as you use the towers that come with the newer cam. They have larger journals than the 78. The newer cam also has slightly different timing/lift specs, but works fine. Be sure to use the cam followers in the same order from the new cam as well. Mismatched used parts can destroy each other in very short order.

no, my 84 240 has the broken cam, I will be pulling the cam and towers from the 78 and putting the whole thing onto the 84. any issues forseen with this? I will swap the followers also, I didn't think of that, but it makes total sense, thanks!

leathermang · #5 04-16-2010, 12:12 PM

You should read the FSM carefully before you do this. type of metal in cam/caps/ followers, etc... not sure off hand... just that I remember reading about matching up things at one time... . and you do seem to be stepping over the time line which would promise that packages would need to be installed together...
I guess you understand that you will be using a cam which gives less HP ?

Do you have a paper 616 manual to read /study ?

Johnt49 · #6 04-16-2010, 12:32 PM

No problem as long as you use the whole package (cam, towers,& followers). Any HP difference will be minimal since you still have a basically euro engine less the cam.
Be sure to rotate the eng through several complete cycles by hand after you're done to make sure there are no clearance issues since you're not sure of the condition of the valves.

vstech · #7 04-16-2010, 12:34 PM

no, I do not have any FSM's aside from the cd's.

leathermang · #8 04-16-2010, 12:36 PM

Are your cd's the 616,617na manual ?

vstech · #9 04-16-2010, 12:38 PM

heh, I've actually never used the CD's (this forum is just wonderful) so I have no idea what's on them. I got them off ebay, broke one set, and ordered another, and STILL have not used them.

leathermang · #10 04-16-2010, 12:42 PM

LOL,
you have fallen into a common trap. It is so much more fun to be interactive than to read really dry literature... but I have warned many times that the forum answers... and even the Haynes manuals OFTEN leave off serious Warnings .... the FSM info can really save some serious little mistakes which can cause huge problems... if not followed to the LETTER.....

Johnt49 · #11 04-16-2010, 12:45 PM

Unless you're willing to wait until a euro cam package shows up, don't waste time over thinking it. It will work! Been there, done that. It's not a difficult job, just be thorough. You're not building a racing engine, just reviving a good old runner. If the parts pass a good visual inspection & you're comfortable with the source put it together & enjoy the drive.

leathermang · #12 04-16-2010, 01:02 PM

John , I suspect you are correct...but you can understand that since he really does not know what caused his cam to break... he is snake bit about just doing the change over without perhaps addressing whatever was the problem.

Johnt49 · #13 04-16-2010, 01:17 PM

I'm not suggesting he over look the cause of the failure, just addressing his question about parts interchangablity.

leathermang · #14 04-16-2010, 02:07 PM

So you are sure ... in terms of things like base size of the cam towers, bolts to be used, etc that he has no problems facing him just transposing what he has described from the parts engine to his engine ?
Or does he need to look carefully at the 616 manual ?

vstech · #15 04-16-2010, 11:01 PM

since I am not in a hurry, I will load up my cd's (assuming I can find them... ) and look over the issues of cams. I sincerely doubt the manual will have any info on swapping a set of towers/cam from an older motor...
Hmmmm. I wonder what the cost is on a new cam designed for this motor...