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#1
11-15-2002, 03:57 PM
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603 upper chain guide and cam timing
The CD manual isn't specific on which way a new upper chain guide should be installed and I didn't note how the old one was installed because it was removed from the head at the machine shop.
The CD manual parts diagram shows that the angled brace goes on top and the perpendicular brace goes below. The picture isn't clear enough to show whether the circular retaining pin hole or the enlongated retaining pin hole goes on top. I'm really scraping for words to describe this  Does anyone understand what I'm saying and know which way to install the guide? I put it in as the parts diagram shows based on the braces which puts the enlongated hole below.After replacing the head, I can't get the cam and crank pulley to read TDC at the same time. The tensioner is not in place at this time. With all the slack on the tesionser side I have the cam a little BTDC... at least as far as I can tell because the crank pulley marker isn't exactly a point. I plan to check again after the engine has run and the tensioner is pressurized. Any guidance until then? Thanks, Sixto 91 300SE 87 300SDL 83 300SD 
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#2
11-15-2002, 04:06 PM
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From memory, I think the rail only fits properly one way, if not, I think you are correct that the elongated hole is the lower one. It's been almost a year since I did this but I do understand what you mean!
 About the timing. If your chain is not new, you'll never get them both at TDC. The tensioner doesn't matter, it is on the "slack" side of the sprockets. Crank until the cam tower marks are lined up perfectly then read the number off the crank. Repeat several times so you know your reading is accurate. Mine is 4 degrees ATDC, which means my timing chain is stretched 4 degrees and needs replacement (I'm changing it in the next week or two.) Sounds like you have the same problem. Here's some light reading for you: http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain.pdf Notice that the TDC pointer is adjustable over a 3 degree range! I set mine with a dial gauge while the head was off, measuring off the piston crown. My indicator was off 1 degree, now it's fixed. After you get the head on, also check the IP timing, which should be 15 ATDC with the lock tool, I recommend setting it a little advanced, say 14 ATDC. Regards,
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#4
11-15-2002, 06:18 PM
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Uh - silly question, but how do you measure the IP with the crank at TDC? The normal procedure is to use the lock tool on the IP, which fixes it at 15 ATDC, and then the crank should read 15 ATDC... I'm confused as to what you're reading/setting!
 Regards,
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#5
11-17-2002, 05:07 PM
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That came out all wrong.
I meant that the IP's as close as I can get with static timing given the potential inaccuracy of the crank pointer's placement and my inability to read it with any confidence. Sixto 91 300SE 87 300SDL 83 300SD
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#6
11-17-2002, 09:16 PM
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Ah - gotcha. To reduce the possible error factor, when I check the cam and/or IP timing, I do it 3 or 4 times, rotating the engine twice for each time. When I get the same reading over and over, I know it's really close. According to Dr. Booth, a few degrees of cam timing variation doesn't make much difference in power or MPG. He also says the same of IP timing, but my experiments have shown a possible improvement in MPG with the IP set on the advanced side of spec (14 instead of 15 or 16.)
I should be doing my chain in the next 2-3 weeks, the tools have been ordered and should arrive shortly! Regards,
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