What Next? Cam Timing Question 107 560
 

Well, I'm in the middle of doing the RH head, and the timing marks on the LH cam, RH cam and the balancer were at dead zero. So, I remove the RH gear, and, surprise, the cam moves about 15 degrees to the right (CW) (7.5" chain stretch?). It is now in a position that I will not be able to put the chain and gear back on, now that I have replaced the tensioner arm and chain guide (the tensioner is NOT on). The engine has not been otherwise moved; the LH mark is lined and the mark at the harmonic balancer is a 0. I haven't touched the engine afer changing my pants.

Questions:

1. Can I turn the cam BACK to its original position at the RH line-up mark? Seems like this is reasonable (it was there before...).

2. How?

I don't think that I can use the bolt (not to go backwards (CCW), anyway).
I can remove the plugs to remove the compression
I can remove some (but not all) of the rockers.

I've been thinking of making a tool out of some strong bolts and metal, to put in the holes on the gear.

BTW, my plastic guides looked like crap (brown) at 87K, the arm had two good-sized grooves in it (original? the Swag replacement is smooth), and the tensioner was REALLY, REALLY loose (felt like just the spring in there before I took it off).

I'm really being cautious about the next step...

PS to above: I have the gear and chain marked to keep their alignment, of course.

There should be a hex head section on the cam that you can use a wrench on to rotate the cam. On my 1992 300SE, it was at about a third of the way from the rear cylinder.

Tim

No, no such luck on mine. There are a few "tabs" in the middle that look tempting - but I'm worried that I might slip and ruin a surface. MB sells a very expensive aluminum tool to hold the cam in place while you are removing the gear (like, $75 at samstag) but I'm still looking to turn the gear and $75 is a lot of dough to pay for an aluminum handle. A strap wrench looks tempting but I need very fine control and will (if someone more experienced can tell me if this is safe - see post, I only need to get it back to where it was before compression pushed it - but I'll probably make a tool out of a metal bar and a few sturdy bolts.

You may wonder, "how did this happen - you should have removed the rockers first, then it wouldn't have moved". Well, according to the manuals you don't have to do this when changing the plastic guide and tensioner arm. But, In order to take the guides off, you have to take off the gear. This is mentioned in the manuals for the RH parts in both MB and Chilton, but NOT for the left in either!!! (GRRR). This is what I get for reading them.

Just take the chain tensioner out and and using the bolt on the cam spocket rotate the cam to the correct setting.

Those tabs are the wrench points. I found an adjustable wrench was barely enough for a good grip with about 22mm, although a slightly larger wrench would have been better. If you're worried about slipping, use a large set of pliers with either rubber boots, or a shop rag to protect the cam. The grip should keep you from slipping. A wrench should be good enough.

Also, There are only 2 ways to get the sprocket on the cam, sprocket facing forwards and backwards. They index so that the sprocket is always timed to the cam. You'd change that using woodruff keys. As long as your chain, and sprockets are marked as to position, and your crankshaft doesn't move, you're fine.

Thanks, this is probably the way I'll do it. Although, incredibly, I don't have an adjustable wrench of this size (ha ha), I'm going to need one!

On the timing, that is the deal - if the lines are lined up (and didn't go around once, heh heh...well, not so funny:eek: ) it must be good. I just wasn't expecting the cam to spring forward.

You can also just use the cam gear bolt. If the tensioner is out, there should be enough slack to instal the cam gear, hold the chain up off the teeth and turn it to your desired position. I used to be extra paranoid about the timing chain, but from doing some work and watching my mechanic, it seems that you really dont have to get that crazy with it. As long as all the marks line up you are okay.

Check everything first by rotating the engine by hand, all the way around a couple times, to make sure no valves are hitting before giving it a whirl with the starter.

BTW, you dont need the special tool from samstag. Just put a long socket extension through the hole in the cam gear and wedge it against something solid.

cam timing
 

i did the chain tensioner and guides on my 1998 e 430.mercedes makes a tool ( can be bought from dealer) that bolts to the head using the threaded valve cover bolt holes.this tool locks the cams in place during your chain replacement,don"t know if they have the same tool for your car.