Chain tensioner...which way will it draw cam? - PeachParts Mercedes-Benz Forum

greenacres2 · #1 11-07-2003, 07:44 PM

'89 560 SEL. Cover off chain and rails with new tensioner (due to broken rails, which took out the lower left rail). Turning by hand, the Left cam timing mark is dead on at TDC #1. Right mark showed slight retarded (about 6 or 7 degrees on crank). Didn't think we jumped a tooth, but loosened the tensioner and advanced the Right one tooth. Now right is advanced 11 or 12 degrees on crank, left is still on the money. I am assuming that the new tensioner, when under pressure will alter the cam timing slightly. Question is, which direction? Will it pull the right cam gear back from the advanced position? Am i better served to stay advanced or should i go back to retarded but closer?

For what it's worth, while I am quite sure we didn't jump a tooth, when the left rails let go, the left cam ended up exactly 180 degrees opposite the right. Heard no major metallic noise, and can see no marks on the top of any left side pistons (using a flex light and mirror) so my fingers are crossed on bent valves.

Thanks for any help you can offer. And for those lingering to do chain and rails, just do it!!

sixto · #2 11-07-2003, 10:21 PM

Instinct says the tensioner will draw the right cam CCW (in the retard direction). I would hold the left cam still and turn the right cam manually CCW to take up any slack in the chain the short span between cams. You should be able to get the right cam to line up this way as a check. Then install the tensioner and check again.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD
78 450SEL (sold)

greenacres2 · #3 11-08-2003, 09:14 AM

That's the logic I was leaning toward, just checking. Heading out in a minute to finish putting her back together. Test fire by this afternoon???

mikaelw2001 · #4 11-08-2003, 10:45 AM

Do remember to have the tensioner installed when taking the redings of the timing. Otherwise You will get a false reding. Dont ask how I know!!

Good Luck,

Mikael Westerberg
1984 500 SEL
Vanersborg Sweden

stevebfl · #5 11-08-2003, 12:12 PM

Put the tentioner in and roll the motor by hand a couple revolution back to TDC and look again. That is as good a reading as you will get without a dial indicator. DO NOT leave it advanced.

The natural place is for the right cam to be slightly retarded as there is way more chain between it and the crank. Even with a new chain the wear of the gears causes the same action (right cam retarded).

The marks you are using are good enough to pick the right chain position. They ARE NOT accurate enough to judge the degree of retard or advance. This must be done with a dial indicator. Years ago I used to dial indicate them and correct to within two degrees with offset keys. On an old chain with 14 degrees of retard this would really bring back some power.

It has been years since I quit doing this. We now roll through a new chain if it had that amount of retard and accept 5-6 degrees that they always seem to show (on the right cam).

greenacres2 · #6 11-10-2003, 08:10 AM

Rough, but she runs. And a few oil drips to chase down. But then engine fires and smooths at speed.

Steve...Thanks, I took the right side back to the slightly retarded mark, the engine rolled smoothly by hand several times, marks ended up in the same place each time. I may pull the leftcover off tonight and see if the right has moved at all.

When i started her last night, she started hard (several seconds of cranking and had to depress the accelerator pedal) and ran very rough. Started with difficulty several times. Seemed to smooth at 2000 rpm, but i think that is just speed taking over. This morning, she started much easier (flick of the key) and seemed a little smoother, but still very rough. Vac lines all seem to be there. I did wipe out the distributor cap with a brake cleaner so i will pull the cap and wipe thoroughly with a clean dry cloth.

Here's to the PROS!! Cover off timing chain, all new rails (including bottom), valve stem seals, belts, oill pump chain and tensioner, EHA, and other assorted gaskets--3 weekends, much sweat and tension. I don't think i could do this for a living, and the process has given me a much greater apprecaition of all who do. Thanks for all the input from those who did.

stevebfl · #7 11-10-2003, 11:21 AM

When you first started your lifters were probably extended due to the rockers being off. We usually compress all the lifters before we reassemble. They eventually recede back to the proper position.

This causes the valves to hand open.

greenacres2 · #8 11-10-2003, 11:29 AM

Was better this morning. Am also going to change the o2 sensor tonight, as she was consuming oil at about a quart every 250 miles before the work. I can tell from the exhaust that the valve stem seals made a world of difference. No black spot on the floor after idling 10 minutes. Will driving some help the lifters settle back in?

stevebfl · #9 11-10-2003, 11:57 AM

They have already settled.

greenacres2 · #10 11-10-2003, 08:19 PM

Dang, i'm sorry to hear that. New o2 sensor helped a little, but the vibration is so bad that it doesn't smooth out until about 2000 rpm. From there up, she smooths out enough that a passenger might not notice. Wiped out the inside of the distributor too, to no avail. Not like a miss, all cylinders feel like they are firing. Will hang in there. Thanks again Steve.

MikeTangas · #11 11-11-2003, 01:56 AM

Earl,

Look carefully, with a flashlight, under the intake. Make sure all of the vacuum lines are attached to their ports. Should to 2 maybe 3 on the left side of the body and one at the front. If I recall, one of those on the side is actually just a tad to the rear of the others.

If any are loose, all you need is a 12" pair of needle nose. They will let you reach way back under the intake to slip the rubbers back on the nipples.

greenacres2 · #12 11-11-2003, 09:32 AM

I remember that from your work on Blitzen. Have a flex shaft pen light and small telescoping mirror that i stole from guitar tools stash that are just perfect for that stuff. Also, before i started on the chain, i had the fuel distributor off and did not renew the o-ring, so i will do that too.
Have new injectors, holders and air supply lines on the shelf, with all the work on the top of the engine, the old brittle parts may have been dislodged so there's another avenue. Finally, i have a slight tap on the left side of the engine--exhaust valve bent?? I sure hope not.