Engine rebuild with no former experience........

Hi Jim,

Gullydeckel-Martin, who once ordered the hoses for us, recommended using brake cleaner before pushing on the hoses. Makes it easy to get them on but has no lubricating substances that could weaken the stability of the connection.

Regards,
Lutz

Thanks guys, I tried that technique and it worked.

I admire what you are doing, wouldn`t have 10% of your energy and your skills !

Kalli

Skills can easily be learned, I had never worked on a car before I bought this one. Time cannot easily be bought though, and this hobby is very time consuming. I am very thankful for early retirement.

Killing time this morning before heading to the machine shop to pick up the CAMs.

Starter motor and solenoid bolted back together.



Need to sort out a couple of new screws there.:ashamed:



The full engine rebuild gasket set wasn't as full as it could have been, so cut out a couple of new gaskets.





Oil pump damper back together.



Then off to pick up the CAMs. The left CAM perfectly on the target size. And rotates perfectly with all the cam towers bolted down.





The right CAM is not so good news, it has had the leftmost two journals ground (1 and 2). The far left is perfectly on size at 49.275 but the next one in is oversize at 49.28, however even with that there should still be a bit of clearance if everything was concentric. When I tighten down tower 2 (with the others already tightened down) the CAM shaft binds up (worked it out through a process of elimination). It's no big deal and I am sure the machine shop will be able to sort it out, but they are now closed till next Monday so I will have a bit of a delay.

All's well that ends well.

We can assume that new set of bearings from Mercedes will be concentric.

We can also assume that there may/will not be concentricity between two different sets, regardless of whether they are the standard size or undersize. This can be deduced from the fact that Mercedes will only sell a full set.

So mixed sets will have the chance of not being concentric.

When fitting a new undersize bearing set, you must grind all the journals at the same time on the same set up to ensure concentricity.

If you only grind one or two you are guaranteed to have some amount of non concentricity between the journals.

What happened to me was very unlucky, I ordered (from ebay) what I thought were 3 good standard size bearings that turned out to be undersized, non concentricity factor 1.

As a consequence I needed to grind 3 journals on the CAMs, non concentricity factor 2.

The only machine shop I could find that was open (covid) was one I said I would never use again, non concentricity factor 3 as well as grinding one of the journals over size.

From that it is clear that I would be very lucky to have no issue with binding, and I'm not that lucky, so this is what I did today.

Blue up the bearing.



Bolt it down.



Give the CAM a half twist and review.



Then use my contraption with 400 grit emery and a scotch pad applying pressure where needed (yes I know I lots of people will say DONT USE A SCOTCH PAD!) to get rid of the binding spot. It took 5 iterations to get the CAM to rotate smoothly. The bearing was cleaned each time till there were no traces of sanding material.





All done, almost.



Once that was complete I also did a bit of work on the other two bearings with the blue to ensure they were also running perfectly.

Jim the researcher!
Through the scotch pad method you probably took off material not only from the binding spot but everywhere, right?
How can you now know how good the result is (overall tolerance and overall concentricity)?

Regards,
Lutz

Hi Lutz,

No, the bearing tower was not tight on the scotch pad and mandrel, so it was easy to provide force to any quadrant needed to focus on the problem area.

With the bearing in the pictures above I started off with a clearance of 0.02mm which was one of the problems, the minimum should be 0.025mm.

The clearance specification is actually quite wide, 0.025mm to 0.057mm, so removing ~0.015mm of material still leaves me well within the tolerance.

Also, once the engine is running the aluminium bearing expands at twice the rate of the steel CAM shaft, so I have no worries about normal hot running.

I do not have perfect concentricity, but I am not worried about this.

To do this job properly ideally you would buy two new CAMs, two new bearing sets, 16 lifters and ?? shims, ~ £2500, my fix cost £160. Undersize bearing sets are no longer available from Mercedes unfortunately.

Hello Jim,

I would be not to concerned about your "rework"

If you are with tolerance limits and the cam is turning freely in the bearings/ towers everything seems to be aligned good enough.

Just would check if the cam is turning freely in the towers before assembly.
During/ after engine recommissioning listen for any abnormal noise and take the valve cover off and take a quick temperature check of camshaft and bearings/ tower just to check for high temp i.e. friction.

Just make sure the surface of the bearings is free from any scotch pad residues.......your engine would not like this material in the oil circuit.

We scraped bearings on large two stroke cross head marine diesel engines.
When I did this the 1st time I was a little hesitant.......but with advice from my Chief Engineer this worked our very well.
Just need to know what you are doing.

Kind regards

JP

All the new bolts organised for the rebuild.



I was surprised to see that the pistons sit proud of the block at TDC, given there is no recess in the head, that's cutting it close with the thickness of the head gasket, the spec says 0.75mm max projection.



Head ready to go on.



Head in place.



Various brackets and starter motor heat shield held on with head bolts.



Out for a Covid lockdown walk.



New chain guides and sprocket, with head torqued down, the CAM shaft still rotates smoothly!



Other head sat in place, initially I thought "great, the chain meets up as expected", more on that later.



Next a quick check on the timing marks at TDC, left head (from the front of the engine), good.



Right head, good.

Looks like the timing spike on the aftermarket water pump is a bit off, as I know the engine is perfectly at TDC.



So the problem is, the chain is too tight or too short, this is the post on the chain tensioner rail, it should be recessed in the head about 1 or 2 cm. Now I have still to torque down the head but I cant see that giving much more slack! Confused.



The chain is a Febi which should have 198 links which is correct, but I didn't count them.



I'll need to get an endoscope in there tomorrow to work out what is going on.

A frustrating day!

This morning I rotated the engine and pulled the chain all the way through, no snags, pile ups or problems, just went straight through, so there was no issue with the way the chain was threaded trough all the sprockets.

With the chain linked, there is no way the tensioner will bolt on.



I then connected and pulled through the old chain.



It was the same as the new chain, it linked up as long as the tensioner rail was in the wrong position.



So there was no choice, slacken off the heads and remove the timing cover and the upper chain guides. I put the tensioner in place, with the chain pulled tight, you can see that it is still one link too short.





Tensioner peg pushing against the tensioner rail peg.



Next I measured and compared the new sprockets with the old, they were close to identical, I quick comparison of the lower chain guides came up with nothing obvious.

Tomorrow I'll start swapping back in the old parts till I find the problem.

Hi Jim,

can't the chain tensioner be pushed in further? I remember when I changed the guides I was instructed to use longer screws on the tensioner first because I wouldn't be able to push it in by hand.
Unfortunately I don't remember if the peg was protruding as far as yours.

Regards,
Lutz

I think because of all the new items, the rail peg protrudes further than it did before.

Back on track, heads bolted down and a couple of ancillaries bolted on.





Inlet manifold just sat there for the picture, needs to be bolted to the lower manifold first.



Will get the oil pump and sump on tomorrow +++.

Engine flipped over.



Oil pump and its chain tensioner.



Then the sump.





Throttle body and lower manifold.



Upper and lower intake manifolds bolted together.



There are lots of parts to be bolted on.



Progress.



More progress.





Done for the day.

Great work - I admire you skills !

Where do you live ? In not Corona times I am usually once a year in Bracknell......

Kalli

Hi Kalli, not too close to Bracknell, I live just outside of Edinburgh. When I was still working I spent quite a bit of time in Germany, many visits to here.

Hello Jim,

the engine looks great with all the cleaned and new plated parts. I am a little bit confused, what was the solution of the problem you have had with the chain tensioner? As suspected from Lutz that the chain tensioner could be pushed in further ?

regards Markus

Racediagnostics wrote: ...I live just outside of Edinburgh....


 

That's good ... then we can welcome you back on the continent soon ... hats off to your work, looks great! Probably you will get the certificate "best looking M117 on the forum"
Thomas

Sindelfingen. My place of birth 
Impressive work that you show us. Thanks that we can take part of it.