Camshaft timing, guiderails. - PeachParts Mercedes-Benz Forum

milterino · #1 09-08-2006, 09:29 PM

This is first time for me in any of these operations. I changed the timing chain, the p.s. guide rail and the 2 d.s. guiderails. The upper guiderail on the d.s. was broken and was lucky to get it out in one piece before any damage occured. Symtom was a rattling up there for the last year or so which I could never pinpoint.
The problem: I painted the sprocket and chain on the d.s. to assist in reassembly. Well, in the process I rubbed off the paint on the sprocket and had to guess when reassembling it to the cam-chain. I put the sprocket back in what I assumed was the correct position and rotated the crankshaft thru a complete cycle and did not feel or see any obstruction between piston and valves.
Question, the markings on the #1 and #5 tower should match with the marks on the respective camshafts. Is this so? Well when the p.s. marks line up, the d.s. marks are off by about 3/32" or what I figure roughly is 2/3 of a tooth. My plan is to pull this sprocket again and adjust by one tooth in the appropriate direction then roll the crank around to see if I get a better alignment than 3/32", if so use this setting, if not go back to the previous setting. What do you think?
Another situation I don't understand is when the new p.s. cam and tower marks are lined up, the pointer on the crank points to about 6 1/2 degrees a.t.d.c. Any thoughts on what could be causing this?
I haven't changed the lower quide rails or tensin rail. Tension rail is next..
Another thought: Does this sound correct? #1 and #6 cylinders are sort of flip flops of each other. When #1 cam is pointing straight down then #6 cam should be pointing straight up and so forth. Any comments appreciated. Milt.

nhdoc · #2 09-09-2006, 04:31 AM

I am sure others know more than I and will chime in but my understanding is that with a brand new chain you should be able to line up the timing marks on both cam towers to TDC and the pointer on the crank should be at 0 degrees. If you have a new chain installed and don't see 0 on the crank I suspect something is wrong and maybe you jumped a tooth when you rolled in the new chain...but like I said, wait for others to confirm this before you start tinkering again...

cth350 · #3 09-09-2006, 08:44 AM

The relative position of the crank and passenger side aka p.s (in the US) cam are off. The should indeed line up.

Yeah, the paint never stays. My best success has come from two different techniques.

- Use a sharpie pen on the sprocket and on the chain in like 6 places. Make each mark unique and put them where the chance of your fingers rubbing it is slim. With luck, you'll only rub off 5 of the 6.

- Get two metal twist-ties per cam. The thin wire is stiff enough to stay on well and small enough to remove it post-assembly.

Lastly, I recall something about the two cams not lineing up relative to each other quite right until the chain tensioner is fully presurized with oil.

-CTH

milterino · #4 09-09-2006, 10:23 PM

Well, thanks for the reply.The job is still in process. C.T.M., do I understand you correctly. Are you saying that all 76 450SEL in the U.S. have thier timing marks off and thats why the p.s. camshaft timing marks don't match the crankshaft timings marks? Milt.

nhdoc · #5 09-10-2006, 07:50 AM

I think he is talking about passenger side in the US being the right hand side of the engine (in other words LHD) not something about the US version of the engine being any different.

The timing marks should line up on all versions of the engine...most people just say left side and right side instead of passenger and driver since those are not "fixed".

Left side of the car is the driver's side in the US, but it's the passenger's side in the UK. It is always the left side though (as viewed from sitting in the car facing forward, which is the conventional way of telling left from right on cars).

Saying left side and right side avoids confusion here too because we have people from all over the world posting and reading the posts so one man's passenger side is another man's driver's side...get my drift?

milterino · #6 09-10-2006, 10:14 AM

Marty, thanks for your explaination, I should have picked that up. So, now I am in more trouble. I had moved the chain a tooth and was rolling the crankshaft thru a cycle by hand to see if it was O.K. and it looks like I ran the piston into the exhaust valve on cylinder #7. Only slightly, I am sure there is no damage. Big question now for someone, can I reverse the crank and go counterclockwise just a bit to get piston and the valve apart. The cam lobe has just passed over its maximum valve opening location and is on its way up to valve closure. If I get them apart I can then move the chain a tooth to where I think it should be. If I can't pull that off can someone tell me what to do. Milt.

Tomguy · #7 09-10-2006, 10:35 AM

I tried to post this last night but the forums seemingly went down when I did. It may sound dated but here's the post:

Milt: The timing marks aren't EXACT because they can look lined up on the cams but be off a degree which is 2 at the crank. But 6° is a bit much with a new chain and top rails. You shouldnt need to do the bottoms. You aren't off a tooth if you're off by just 6° though. One tooth on the cam = 20° at the crank.

Remember, your cam/washer marks should look like this:
http://www.peachparts.com/shopforum/attachments/vintage-mercedes-forum/34537d1152472986-380sl-timing-chain-stretch-jump-question-tdc.jpg
(The other side has that mark right by the cam oiler tube)

Now since I didn't get this post in in time, you attempted to move a tooth, so you're now 20° off. Hopefully your master link is right by the cam that's off. Remove the chain and turn the cam counterclockwise CAREFULLY by one tooth and reconnect the master link. You don't need to turn the engine.

It's also possible your cams have offset keys installed which makes their timing not on TDC - or it may need offset keys.

milterino · #8 09-10-2006, 03:17 PM

Tomguy:Thanks for your reply, great picture! I don't know if I could recognize and offset key but to me they look just like straight woodruff keys. The master link is hidden down below so that's not a possibility. The locked up crank which I assume is the piston and the valve bumping each other is my present concern. They are just barely touching I think but there is some resistance to moving the crank either way. Can I safely reverse the crank to get them free? Then I think I can pull off the sprocket and make my tooth correction. Milt.

Tomguy · #9 09-10-2006, 03:52 PM

I would try to back off the cam rather than the crank. Hopefully the one will free the other. If not, you'll have to pull that head.

psfred · #10 09-10-2006, 04:48 PM

You can back the crank up enough to take the tension off the valve. No need to open the master link or remove chain.

If you pulled the chain through by the book method, you should be very close to correct except for wear on the sprokets. If the teeth on the cam sprokets are pointed and sharp, replace them as they are worn. If blunt, they are OK, although you may need offset keys to get prefect valve timing.

I would remove the cam followers before doing anthing else. Make sure you put them back in the same spot, else the cam may fail very rapidly. With the followers out, you can mess about all you want and the valves stay completely shut, won't contact the pistons.

Once the followers are all off, crank the engine around to TDC on #1. Leave crank in place, and remove the cam sprokets one at a time, keeping the chain wired to the sprokets. Unwire the sproket and jump the teeth to get the slot in the washer as close to centered as you can on each cam, then rotate engine around while applying some force on the slide rail the tensioner pushes on to get the slack out. Line up the notches and see where you are -- unless something is really off (like the wrong chain), you should be very close to them all lined up at once.

You can then re-install the cam followers and rotate by hand to check for correct valve operation and clearance, and check the valve timing correctly (with a dial indicator) if you wish.

Make sure you don't swap the sprokets right to left....

Peter

milterino · #11 09-10-2006, 07:35 PM

I want to thank everyone for the time you took to help me out here. Now to impose again. What is a cam "follower". This car has hydralic lifters. Is the follower another name for the rocker arms? If I ever have to remove the valve springs is it necessary to use the one they illustrate in the C.D. or can I use a generic valve spring remover sold in the auto stores.
Could I eliminate the pressure of the cam on the springs by removing the cam towers and shaft? Once again, I have never fooled with valves so if some of these questions seem tedious my only defense, if that, is ignorance. Milt. P.S. Peter,the teeth seem sharp to me so perhaps that could account for some of the slack.

psfred · #12 09-10-2006, 09:11 PM

Cam follower = rocker arm, although they really aren't the same.

You cannot remove the left side cam with the engine in the car with any ease, and you don't actually want to anyway, you just want to time the cams correctly.

If the sproket teeth are "poke holes in you if you touch them" sharp, you need replacements, and set the one you changed back to where it was. They wear on one side only, so the u-shape for each "gullet" will be asymetric if badly worn. Typically they also have a burr on that side, but not always.

Have a care when matching up the marks on the cam towers with the notch in the thrust washer, you must look directly down onto the cam tower in line with the mark, and make SURE it is centered in the notch. It's quite easy to think they are lined up when they are not if you don't look straight into them. Move your head around with them lined up and you will see what I mean.

Peter

milterino · #13 09-10-2006, 09:35 PM

Peter, thanks again. I will give it a try tomorrow. Milt.

Tomguy · #14 09-10-2006, 11:12 PM

Quote:

Originally Posted by psfred

You cannot remove the left side cam with the engine in the car with any ease, and you don't actually want to anyway, you just want to time the cams correctly.

I was easily able to remove both sides from my 4.5 about 4 times (NOT including the head jobs). I swap cams to play around with the powerband and see if I can feel a difference all the time.

milterino · #15 09-11-2006, 10:48 PM

Well, guess what happened. After about 24 hrs I tried reversing the crank to unbuckle the piston and valve and it just eased out without hardy any pressure at all. From there it was easy to take off the sprocket and eventually get it as close as I could get it. When the r.h. is dead on the l.h. is about 3/32 off. I think the camshaft must have caught on that I was going to start operating on it and decided it better cooperate. So, thanks to you all, tomorrow I will give it a run on the interstate and try to burn off the gunk on all the plugs. Milt.