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  #1  
Old 03-16-2003, 02:25 PM
1973 450SL 117.982 107.04
 
Join Date: Feb 2003
Posts: 53
Question Camshaft Degree Wheel Question

I went to the Pindelski web sight to see how to check for timing chain stretch so I followed the instructions set the camshaft dead on and checked the Crankshaft degree wheel, on my 73 450SL it showed about six degrees to the right of Zero (ATDC) but on his pics it shows about 7 degrees to the left of zero (BTDC) can the chain stretch show the degree wheel off in either direction or will it always be in one direction and why??
Thanks In Advance for taking the time to comment!!

Razzle
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  #2  
Old 03-16-2003, 09:55 PM
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Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
If the engine is properly set up, it will appear to be AFTER the tdc mark. Yours is correct.

Ideally when new it is at 0 and when the chain stretches the crank will turn in the clockwise direction from the cam.
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  #3  
Old 03-17-2003, 01:54 AM
afmcorp's Avatar
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Location: NW Indiana LaPorte
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this question is for my enlightenment.

i just did my rails/cam replacement and used 4degree offset keys. so as i am looking down on the dampener the timing marks go from 0 right should be "before tdc" and left of 0 should be "after tdc".

if the dampener is rotating clockwise. i would describe your timing before top dead center(to the right of 0). when i added the 4 degree keys the manual shows by making the keys sit in one position (right or left) you advance or retard the 0 point. (in my case the addition of the offset keys brought the timing on the dampener back to about 2 deg after tdc.)

also as i analyze the rotation of the engine when a chain stretches the timing would be retarded therefore you should be reading after tdc.

now i might be miss reading this, my view is from in front of the engine looking in. i know right hand vs. left hand is from the pass compartment.

i'm just looking to clarify for my own piece of mind.
tks
craig
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Craig

1972 350sl Red/Blk 117k
1988 420sel charcoal/Blk 140k
1987 420sel gold/tan 128k
See My Cars at:http://mysite.verizon.net/res0aytj/index.html

Pound it to fit then Paint it to match!

There is only First Place and Varying degrees of last!

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  #4  
Old 03-17-2003, 01:48 PM
Thomaspin's Avatar
pindelski.com
 
Join Date: Jun 2001
Location: CA
Posts: 531
Chaosmosis

Not sure where you are looking on my site, but in this picture, the degree wheel on the crankshaft is ATDC - or, stated differently, the 0|0 mark is to the right of the pointer.
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  #5  
Old 03-17-2003, 02:03 PM
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Chaosmosis


(hi thomas - i'm finally going to start my 88 up this aftn.)

what you are saying is what i was trying to ask. i thought Chaosmosis might be referring to the driver's position inside the car. your foto is showing Atdc so the timing marks are retarded.

Chaosmosis, stand facing your car and where the 0l0 mark is what side is it on right or left and estimate what number it is near. 5, 10 etc:
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Thanks Much!
Craig

1972 350sl Red/Blk 117k
1988 420sel charcoal/Blk 140k
1987 420sel gold/tan 128k
See My Cars at:http://mysite.verizon.net/res0aytj/index.html

Pound it to fit then Paint it to match!

There is only First Place and Varying degrees of last!

Old age and deceit will overcome Youth and Enthusiasm every time!

Putting the square peg in the round hole is not hard... IF you do it fast enough!

Old enough to know better but stupid enough to do it anyway!
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  #6  
Old 03-17-2003, 03:07 PM
1973 450SL 117.982 107.04
 
Join Date: Feb 2003
Posts: 53
Timing Mark

If I am stand in front of the car and look down on the engine the pointer is approx 6 degrees to the right of the zero mark on the dampener.
Thanks for helping me understand this...
Chaosmosis
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  #7  
Old 03-17-2003, 03:30 PM
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Join Date: Jun 2001
Location: CA
Posts: 531
For future reference....

....I added an annotation to that picture to explain that the engine is 7-8 degrees ATDC with the camshaft marks aligned.

It up on the site now.

It's still not clear to me why Chaosmosis's engine is advanced - was the timing chain installled incorrectly?

(Craig - good luck with the '88).
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  #8  
Old 03-17-2003, 04:06 PM
1973 450SL 117.982 107.04
 
Join Date: Feb 2003
Posts: 53
Advanced timing chain

Hey Thomas,
I bought this about 3 months ago so I don't know all the history, the odometer is at 121,320, the chain and guides look new, I found the c clip linkage so it was replaced, my question is will this being advanced cause any engine problems and how would I go correcting the advancement, the car runs excellent now but I do hear what sounds to me like a very slight valve tap on the right side. The compression is between 125-128 on all cylinders.

Thanks Again,

Last edited by Chaosmosis; 03-17-2003 at 04:13 PM.
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  #9  
Old 03-17-2003, 06:15 PM
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pindelski.com
 
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Location: CA
Posts: 531
Hmmmm...

I wonder if offset Woodruff keys were used with the old chain to advance the timing as the chain stretched, and not replaced with straight ones (no offset) when the chain was removed? That could be one source of over-advanced timing. Wonder if your records disclose anything, if you have them? One way to tell is to pull off the toothed wheel on the camshaft next time you have the valve cover(s) off - pix on my site.

It doesn't sound like the new chain missed a tooth - each tooth is 18 degrees and you would porbably have valves coming into contact with pistons if that happened.

Timing really s/b correct with a new chain.
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  #10  
Old 03-17-2003, 06:27 PM
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Chaosmosis

i just read your other post.

so it seems that the engine has had the chain guides replaced at some recent time. so there is no base from which to work.

let's now agree that to the right of 0l0 is btdc and to the left is atdc. but before we go forward i'm going to suggest you resolve the tapping sound first. i'm just getting my 88 back up due to a tiny tapping sound which ended up costing a new cam and set of rockers and i valve compensator. if the valve comp is bad easy fix as long as no damage has occurred to the cam or rocker. so do that first. (note: if the face of the cam and rocker are bad it is likely do to a lack of oil which means you need to replace the oil tube plastic and the inside of the tube needs to be cleaned. these valve train parts seem to be surface treated for hardness. my cam is cast iron because you can tell by the rough surface area. the rocker looks like a steel forging.

once the ticking is repaired you can move on to the timing chain.

you also said you have had the car for just a short time so here is

a few things to look for:

make sure the notch on the right hand (pass) bank is in line with the mark on the cam bearing tower.

now check the left bank and compare they should be close and in the same sector meaning both should come up to their marks about the same time. if the left is already past it's mark as the right is coming up to it's mark then you may have a mis aligned chain....but you said it runs good so likely you won't see this.

the next step would be to look at the woodruff keys. are they offset or straight. now say they were as much as 10deg offset and the new chain installed it is possible your timing could be advanced past 0l0 and would show Btdc.

now in my head i'm thinking that if you have straight keys (not offset) maybe just maybe who ever did the work could have jumped a tooth and gone for the 18deg advancement you get when you jump a tooth. (just like using offset keys except you get 18 deg for 1 tooth.) you see now your description of being btdc would start to make some sense to me. other guys can correct me if i'm wrong but even a new chain has no guarantee of bringing the timing marks back to 0l0 (tdc) which is basically what we are trying to do.

as far as working ok or functioning properly i think it will. ( you've already said it works ok now) ignition timing is relative. you pull the vac tube or not then you turn the dist clockwise to advance ccw to retard. (i have a 72 350sl which is just like your 73 450sl and i will be working on it from the weekend on) i understand my 87 & 88 doesn't work that so turning the dist does nothing. but these have points and dwell etc so i'm thinking they should work similar to us ignition timing.

so with all this said it would seem to me that you'd adjust the dist till you acheive your idle setting of ??. then as you raise the rpm you can physically see your total advance timing probably some where of 30 deg or so.

but make no mistake about the tapping if it is in the valve train you need to address that first. cause who wants to go back in there in a month or so.

i would think that once you've figured out how your engine is set up it will all fall into place of how it works. you compression looks tolerable so no apparent reason for it to not run good.

get yourself a sprial bound note book like 5 x 7 and document every thing you do no matter how trivial. like your compression oil change dates gas mileage all the above info you're going to get after checking the timing out.

good luck and keep us posted
tks
craig
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Thanks Much!
Craig

1972 350sl Red/Blk 117k
1988 420sel charcoal/Blk 140k
1987 420sel gold/tan 128k
See My Cars at:http://mysite.verizon.net/res0aytj/index.html

Pound it to fit then Paint it to match!

There is only First Place and Varying degrees of last!

Old age and deceit will overcome Youth and Enthusiasm every time!

Putting the square peg in the round hole is not hard... IF you do it fast enough!

Old enough to know better but stupid enough to do it anyway!
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  #11  
Old 03-17-2003, 09:05 PM
1973 450SL 117.982 107.04
 
Join Date: Feb 2003
Posts: 53
Talking Thanks t o everyone

I am starting to understand how this all works, you guys have been very helpful, I willl start that book Craig; sounds like a good Idea and Thomas thanks to you for the great web site, and thank you benzmac. I will keep you all updated. Now I know why you guys love your MB's!!! I have the Factory CD as well as Chilton's so hopefully my learning curve will be less painless....
I will let you know how it works out....
Thanks Again
Chaosmosis
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  #12  
Old 05-03-2003, 08:33 AM
1973 450SL 117.982 107.04
 
Join Date: Feb 2003
Posts: 53
Follow Up for Thomaspin or anyone!

1973 450 SL engine 117.982
Still trying to figure out the mystery of timing chain being advanced 7 degrees (BTDC). In my Chiltons book on page 3-54 under valve timing after gasoline engines.

Item 4. With a 27mm wrench on the crankshaft pulley, turn the engine in direction of rotation, until the TDC mark on the vibration damper registers with the pointer and the distributor rotor points to the No. 1 cylinder mark on the housing. The camshaft timing marks should align at this point.

Note:Note: Due to design of the chain tensioner on V-8 engines, the right side of the chain travels farther than the left side. This means the right-side camshaft is approximately 7 degrees retarded compared to the left side, and both marks on each side will not simultaneously align.

This is exactly what I am experiencing but I didn't see anything in the factory cd regarding this and I have not heard anyone talk about this on the forum so I was hoping someone could shed some light on this.
Thanks in Advance (BTDC) ha ha
for your help

Chaosmosis
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  #13  
Old 05-03-2003, 10:26 AM
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Join Date: Jan 2003
Location: Matthews, NC
Posts: 1,356
Just a thought on the NOTE:
First of all, on my 500, with new chain and all new guides, the cams are at 0/0. I believe the 450 and 500 are basically the same engine.
The NOTE says

"Note:Note: Due to design of the chain tensioner on V-8 engines, the right side of the chain travels farther than the left side. This means the right-side camshaft is approximately 7 degrees retarded compared to the left side, and both marks on each side will not simultaneously align."

Where did this come from?
Could anyone explain how the position of the chain tensioner have anything to do with the timing of the cams?

Now back to the cams not being timed the same.
The only causes for this are:
1. The chain wasn't replaced, only broken apart and reconnected with the master link. (It is still streched)
2. There is an offset key in the cam that is off.
3. The idler sprocket between the cams is worn.

Again, food for thought.
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