Con Rod Bearings. One hole or two ?

[tel76]

The condition of the bores reinforces the argument that the con-rods should be fitted the correct way around and shell bearings fitted into the con-rod with the oil holes aligned and supplying oil to the thrust side.

[Rolf-Dieter ✝︎]

I like to say a word or two, having worked 18 years in an engineering office and 35 years in the field with medium and large rotating equipment up to 300 MW as well as gas turbines in my working life. I've drawn and handled in the field many different sizes of bearing shells. Even on a large turbine the number 1 bearing is of the shell design.

Bearing shells and there respective housings should have been so designed and machined in the first place so that the bearing shells cannot be installed incorrectly by anyone. On other rotating equipment be it large or small (pumps, blowers, compressors, turbines [steam or gas] and other machinery this is the way it is done. The housings and bearing shells are machined with notches so that installation is foolproof all the time.

It is my humble opinion that the Mercedes design team overlooked this and never ever admitted this. Or they made those bearings so that they could be used in different engines. I further think that if a change was to be made like changing, like eliminating an oil hole or blocking it this then was only communicated to OEM shops period.

Auto manufactures don't like to admit they made a mistake, only when it becomes a serious safety issue do they issue recall instructions. Case in point unrelated to bearing shells and going off topic for a moment. I drove a BMW Z4 3.5 is with a 19 inch run low profile flat tire in 2009 when that car was interduced. I loved it since the roof was retractable and I wanted to take a trip across the U.S. along Route 66. I did this, unfortunately I ended up with a cracked wheel in two places. BMW did not replace my cracked wheel (model 296) the argument they put forth was that I had gone thru pot holes and that I caused the cracks. Many other Z4 drivers had cracks in exactly the same places and always the rear wheels. I knew why those failures occurred however my argument went against stone walls so to speak. It took 5 years and several class action law suites BMW now finally replaces those failed wheels. Sorry for briefly going off topic I just wanted to give a personal example.

Back on topic, rest assured if the housings and bearing shells would have been designed and manufactured correctly in the first place we would not be talking about this now. I'm of the same frame of mind as Joe A. When you take something apart and/or replace components, replace them with the same component in the same way as removed. Unless instructed otherwise by a higher level like the factory, product service or a outhorized vendor that gets there instructions from the manufacturer.

Bottom line, if you are not 100 percent sure when you take something apart take photos before you do and then put it back together excactly the way you found it be it the same part or a new one. Your photos will guide you and you never will be unsure. Those are my two cents on the subject.

[Benz Dr.]

The condition of the bores reinforces the argument that the con-rods should be fitted the correct way around and shell bearings fitted into the con-rod with the oil holes aligned and supplying oil to the thrust side.

Thanks for your POV. The extra oil you deem so critical is the exact reason why you shouldn't do it.

The connecting rods are in backwards but like a number of things in these engines, they can be installed either way. Small modifications or updates aside, the more knoweldge and expirience you have doing something the more likely the results will be satisfactory.
 
I asked about the score lines in the cylinders for a reason. Score lines that go to the very top edge of a cylinder indicate overheating, as in running your engine out of coolant or a broken fan belt. This damage is usually fatal and it can be found throughout the whole engine. Warped head, warped block, damaged pistons, scrored cylinder walls and many damaged seals and gaskets. Your engine would need a complete rebuild.This should not be confused with running too lean where the spark plugs will be burned away and the top of the pistons will be burned up or actually burned through.

 The only way oil can get into the cylinders on a fresh rebuild is either through the head ( which I feel is the most common ) or past the rings. If you are pouring far more oil on to the cylinder walls than what is actually required, and there's nothing wrong with the head, this would be a good suspect for high oil consumption. Remember, the complaint when these cars were still new, and under warranty, was that of high oil consumption. These being factory built, with an obvious design flaw, they were quickly replaced by MB dealers. Is there some other clear reason for a brand new factory installed and assembled engine to drink oil and then have be replaced under warranty? I think one can safely assume that it was asembled correctly by a highly trained work crew and that it wasn't a manufacturing flaw.

[Benz Dr.]

I like to say a word or two, having worked 18 years in an engineering office and 35 years in the field with medium and large rotating equipment up to 300 MW as well as gas turbines in my working life. I've drawn and handled in the field many different sizes of bearing shells. Even on a large turbine the number 1 bearing is of the shell design.

Bearing shells and there respective housings should have been so designed and machined in the first place so that the bearing shells cannot be installed incorrectly by anyone. On other rotating equipment be it large or small (pumps, blowers, compressors, turbines [steam or gas] and other machinery this is the way it is done. The housings and bearing shells are machined with notches so that installation is foolproof all the time.

It is my humble opinion that the Mercedes design team overlooked this and never ever admitted this. Or they made those bearings so that they could be used in different engines. I further think that if a change was to be made like changing, like eliminating an oil hole or blocking it this then was only communicated to OEM shops period.

Auto manufactures don't like to admit they made a mistake, only when it becomes a serious safety issue do they issue recall instructions. Case in point unrelated to bearing shells and going off topic for a moment. I drove a BMW Z4 3.5 is with a 19 inch run low profile flat tire in 2009 when that car was interduced. I loved it since the roof was retractable and I wanted to take a trip across the U.S. along Route 66. I did this, unfortunately I ended up with a cracked wheel in two places. BMW did not replace my cracked wheel (model 296) the argument they put forth was that I had gone thru pot holes and that I caused the cracks. Many other Z4 drivers had cracks in exactly the same places and always the rear wheels. I knew why those failures occurred however my argument went against stone walls so to speak. It took 5 years and several class action law suites BMW now finally replaces those failed wheels. Sorry for briefly going off topic I just wanted to give a personal example.

Back on topic, rest assured if the housings and bearing shells would have been designed and manufactured correctly in the first place we would not be talking about this now. I'm of the same frame of mind as Joe A. When you take something apart and/or replace components, replace them with the same component in the same way as removed. Unless instructed otherwise by a higher level like the factory, product service or a outhorized vendor that gets there instructions from the manufacturer.

Bottom line, if you are not 100 percent sure when you take something apart take photos before you do and then put it back together excactly the way you found it be it the same part or a new one. Your photos will guide you and you never will be unsure. Those are my two cents on the subject.

MB is like a dog on a bone - they won't let go. Think of 380SL timing chains and the 129 engine wiring harnes. Both were a disaster and both were up to the owner to sort out because their cars were out of warranty.

[tel76]

Thanks for your POV. The extra oil you deem so critical is the exact reason why you shouldn't do it.

The connecting rods are in backwards but like a number of things in these engines, they can be installed either way. Small modifications or updates aside, the more knoweldge and expirience you have doing something the more likely the results will be satisfactory.
 
I asked about the score lines in the cylinders for a reason. Score lines that go to the very top edge of a cylinder indicate overheating, as in running your engine out of coolant or a broken fan belt. This damage is usually fatal and it can be found throughout the whole engine. Warped head, warped block, damaged pistons, scrored cylinder walls and many damaged seals and gaskets. Your engine would need a complete rebuild.

In the case of a cylinder/s running hot you will have a different set of damages. The scoring will be the height of the top compression ring and will run as low as the ring moves. This is caused by too much oil entering the cumbustion chamber. This is often found as leaking valve guides but it can also be caused by incorrect installation of piston rings or excess oil on the cylinder walls. This damage will be more pronouned on a fresh engine with full compression and as an engine wears out extra oil moving up past the rings will not be as critical.  This should not be confused with running too lean where the spark plugs will be burned away and the top of the pistons will be burned up or actually burned through.

 The only way oil can get into the cylinders on a fresh rebuild is either through the head ( which I feel is the most common ) or past the rings. If you are pouring far more oil on to the cylinder walls than what is actually required, and there's nothing wrong with the head, this would be a good suspect for high oil consumption and scored cylinder walls. Remember, the complaint when these cars were still new, and under warranty, was that of high oil consumption. If the cylinders were running hot because of excess oil entering the cylinder thereby causing the walls to score, then it would really use oil. These being factory built, with an obvious design flaw, they were quickly replaced by MB dealers. Is there some other clear reason for a brand new factory installed and assembled engine to drink oil and then have be replaced under warranty? I think one can safely assume that it was asembled correctly by a highly trained work crew and that it wasn't a manufacturing flaw.



Well I have heard/read it all ! SCORING CAUSED BY TOO MUCH OIL !What a load of cobblers, as you will respond to that comment I will let you have the last word on the subject (AGAIN).
The members reading all the above will have to make there own decision on how they do the work on there engine.

[mbzse]

.../... It's lucky we've picked this up early as this engine was heading for a very premature demise

Colin, fortunate owner of that car/engine, indeed, that he ended up with his car in a workshop that knows what they are doing...
Apart from the two items discussed (Main bearing shell misplaced and con rods put in backwards, as Eric, Dan, JoeA and myself identified) were there additional issues with the previous assembly of this particular engine?
For instance, was the sealing rubber ring on top of the oil filter insert in place...?
/Hans in Sweden
.

[Benz Dr.]

Just a bit of explanation for everyone:
 The rod bearings I get from Metrics only have one hole, which is in the center of the bearing, and it's there for the early style connecting rods used on 230SL's. There was some confusion on my part during these discussions because I was not receiving bearing shells with the extra hole for oiling the cylinder wall. Having never seen this particular bearing type before, ( because that was what I was sent ) I asked Mike at Metrics if I should copy what came apart and drill the extra hole. He said no and I've added his comments to this thread, or another, for clairification only.

For the most part, you can't improve that much on MB design. There are times when you can use a modern method or part such as electronic ignition, which is actually a complete change from what was installed; it works OK and for those who don't want to change ponts and it offers a fairly good alternative.
 However, MB is not infallable - they make mistakes but are generally loath to admit to them. 280SL oil consuption was one of those rare mistakes. It looks like there wasn't a recall issued ( if they even did that back then ) and the problem was likely addressed on an ''as fail '' basis. This is fairly common where there's no recall but the item is still under waranty. No such luck for the single row timing chains in 380SE/SL engines. Most failed after several years and 50K miles so you were on your own. So much also for owner loyalty.


 Since I was never formaly trained, I asked a lot of questions and I made it a point to pick the brains of experts who knew what they were doing. This is exactly what members of this forum do every day - they ask questions of people who know these cars. However, quoting experts does not make one an expert as well and a great deal of expirience and knowledge generally has to enter into the picture first.
When I started back in 1977 I knew next to nothing about old MB cars and there was no one to ask and no one to go to for answers. One had to figure it out on their own and those few who did know didn't give it up willingly. Be very happy you have a place like this where you can find just about any info you need - even if we don't always agree upon the answers.  


This is also covered below in these posts and also first hand testement from owners back in the day who had engines replaced due to high oil consuption.

http://www.sl113.org/forums/index.php?topic=15740.0

 
 

[stickandrudderman]

For instance, was the sealing rubber ring on top of the oil filter insert in place...?

This, at least, was found to be correct.