Lower chain rail replacement

[mulrik]

I found a peace of the left (in the cars direction) lower chain rail in my oilpan yesterday. I suspect it has been there since summer 05 when I had a serious breakdown. The car has been running great since it was fixed, but now I'm in the progress of replacing the cranksprocket, camsprocket and the chain. Is it possible to change one or both of the two lower chain rails with the head on and the engine in the car? What might I risk by running without the broken chainrail and 1/4 of the broken chain rail still unaccounted for (read: still in there somewhere).
BR
Ulrik
Oh one thing. It is impressive how much knowledge you guys have collected. It is truely amazing!!!! When I exemplify people with the knowledge of this forum, they shake their heads in awe!!!

'67 250 SL Papyrus White 113043-10-000023

[Benz Dr.]

If the chain is tight it shouldn't give too much trouble. However, things do happen.....

You need to remove vibration dampner and hamonic ballancer before you can remove the lower chain rail pin. Run a tap down the threaded hole in the chain rail pin before you try to remove it. Not doing this can be a VERY big mistake.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[mulrik]

I'm sorry Dan, but could you explain in greater detail what that big mistake might lead to? Also to be perfectly sure; To run a tap into the threaded hole of the pin means that i put something (a tap??) in to the pin (which is hollow??) to make sure that something doesn't fall down (the big mistake??)inside. But how do I fit the new guide rail then? If you have the time it would be great if you could explain it a little more, and could you also explain what you mean by a tap? My english tells me it is something you draw water from.....
Best
Ulrik


'67 250 SL Papyrus White 113043-10-000023

[waltklatt]

BR,
The 'Tap' that Dan is talking about is to use a thread chaser.  Meaning to clean out the thread grooves before inserting anything in there first.
The threads can be host to all kinds of nasties and the more gunk in there the less opportunity for the bolt(with a small slide hammer) that will be inserted into there has to grab onto-thus leading to a stripped thread.  It will be a tough job if it is already stripped.
So again it's a thread chaser- tap.
Walter Klatt
1967 220SL-diesel
1963 230SL-gas

[mulrik]

OK got it, albeit slowly....
As I mentioned earlier; you guys are fant.....!!
Ulrik


'67 250 SL Papyrus White 113043-10-000023

[ja17]

Hello BR,

Replacing those two lower rails  with the engine in the car is very difficult. Are you doing the work yourself?  As Dan mentioned you may be ok for now if your timing chain and sprockets are good.  Which sprockets were you going to change?

If you plan on doing this job you will need to remove the hood, a lot of things on the front of the engine and possibly the small steel oil pan. Naj is going through a very similar ordeal right now. Let us know your intentions and we will help!


Joe Alexander
Blacklick, Ohio

[Naj ✝︎]

Hello, Ulrik,
My mech changed the sprockets and chain with the head on.
The hood and rad will have to come off as Joe says. Also, the oil pan and front main bearing, to make room to be able to knock off the crank sprocket.
With the chain out of the way, the two lower rails were changed. I was not able to watch over the whole process, so can't say how difficult it was.
On my 230 pump drive sprocket, there was a single punched timing mark. I would take off the distributor drive housing in front of the engine and see where this mark is in relation to TDC before taking the chain off. I'm sure it has some relevance as even though he's got the engine running, he's unable to locate the distributor in the original position. I may play around with that once I get the car home.
The long rail is still available in aluminum with lining but the short ones are plastic only. I opted to fit all plastic ones. What ones were you able to get?

New sprockets, chain and plastic rail:
Download Attachment: TimGr_sprkt.JPG
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naj

65 230SL
68 280SL

[mulrik]

Thank you
Now that I am at it we (friends and I) have decided to change all sprockets, the short lower rail, as well as the timing chain. All sprockets were very worn and as far as I known it is usually advisable to change the sprockets when you change a chain. So now that we are at it... It is also a good challenge and good fun....

We have the radiator off, waterpump out, distributor sprocket out, oil pan off, front bearing off. We need to remove the servopump as well to get access to the pins that hold the short lower chain rail. I read Joes post an Naj's misfortune and read about taking the cranksprocket out through the front oil seal. Actually, we feel pretty confident. Only thing I'm little worried about is taking out the pins for the chain rail and the chain tensioner sprockets with the slidehammer, but we are going to be very carefull as advised from this forum.

Naj the short rail should be available from SLS in alu (expensive though), but I'm in a state of shock cause of the prices they charge for the distributor sprocket and the two top small sprockets; they are f...... expensive!!

We have set the timing of the crank, cam and injectionpump before so no worries there.

However, I wouldn't go about this much without The Forum, so be sure you'll hear from me if we run into trouble! Thanks for you concern.

Best
Ulrik


'67 250 SL Papyrus White 113043-10-000023

[ja17]

Hello Ulrik,
If you do not have the special slide hammer, special puller or do not have room to use it, you can make a simple tool to remove these pins which requires very little space. It reaqires a spacer (sleeve) and some washers. I will send a photo this evening.

Naj,
Glad to see your making progress. Re-positioning the distributor is easy. Remove the distributor and reposition the gear beneath it. It will pull upward for removal rotate it until it positions the distributor correctly. Be sure to note that the slot in the top of the gear is off-set very so slightly to correspond to the off-set cog on the distributor! do not install 180 degrees off or you will have problems later. Also there should be a small spring between the distributor and this gear (often missing).

Joe Alexander
Blacklick, Ohio

[Naj ✝︎]

 

quote:Re-positioning the distributor is easy

Thanks, Joe,

The mech said he's tried it but was not successful.
Anyway, its something I can play with when I have it back.

Otherwise, he says its running fine.

The valves had actually touched the pistons, but luckily didn't bend. Instead, a couple of the rocker fingers were bent upwards and the valve/rocker gap had increased to maybe 0.080. We just replaced those 2 rockers.

naj

65 230SL
68 280SL

[ja17]

Hello Naj,
Yes I have seen this happen. Since the valves are verticle, not at an angle, and the pistons are flat  on top. The rockers may bend, the cam stands may break or the camshaft itself will break as a valve is jambed upward by a piston.



Joe Alexander
Blacklick, Ohio

[ja17]

Hello Ulrik,

Don't be confused by the cylinder head. The pins and process is the same as in the block.

Clean the threads first as Dan mentioned.

Download Attachment: tap a.JPG
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You can make a simple puller with a spacer and some washers. Make sure the spacer is big enough inside for the pin to pull into. Also use a grade 10g  or greater metric bolt.

Download Attachment: simple puller 1a.JPG
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 Download Attachment: sp1a.JPG
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Place the spacer over the pin and when you tighten down the bolt the pin will draw out.


You will have to add washers along the way when the bolt bottoms out in the pin.
Download Attachment: sp3a.JPG
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You will need to make sure that the bolt threads into the pin at least four turns before pulling begins. Pay attention when the bolt bottoms out so you can add washers and keep pulling.

I use a slide hammer when I have enough space.


Joe Alexander
Blacklick, Ohio