Con rod bearings

[bongo666shaftsburry]

Can any one enlighten me regarding con rod bearings? I am attempting to rebuild my '68 M130 and to this end I purchased a set of Glyco NOS con rod bearings, +0.50 mm. Three months after getting the engine back from the machine shop I finally got around to doing some assembly work and to my surprise there are only 5 half-shells that have the oil hole. I have a set of NOS Glyco two-hole con rod bearings for a '67 engine and there are 6 half-shells with oil holes. Additionally, I just bought (as in an hour ago (on eBay)) a set of NOS Glyco con rod bearings with the same exact part number as +0.50mm except they are +0.75 and the photos show 6 half-shells with oil holes. The +0.50 were sealed and they all have the correct (Glyco) part number and oversize stamped on them. Although I can see that, perhaps, cylinder #1 piston might be OK without additional oil cooling due to its proximity to the chain chamber, why would the +0.75 have six oil spurting bearings?

[tel76]

You should have six half shells with the oil hole, there has been a mistake made with the packaging.
You could place the 1/2 shell into the con-rod and drill the hole.
Do you have con-rods with two holes in the rod? if so then you must drill the hole that supplies oil to the thrust side of the block.
You must also re-fit the con-rods so that oil hole will supply oil to the thrust side.
Why did you purchase another set of shells of a different size than the ones you require?

[bongo666shaftsburry]

I have con rods with one oil hole. If I drill a hole should I drill from outside in or vice versa? My concern is how do I make sure that the bearing surface is sufficiently smooth to avoid damaging the crankshaft journal? Can the bearing be polished after the drilling without affecting its longevity?
The +0.75s were cheap and I figured if I could not find the +0.50s at all or at a reasonable price I could, maybe, have one journal machined to the third oversize. And if that's bonkers, then I have a full set +0.75s stashed away for the future.

[stickandrudderman]

DO NOT have the crank bearings ground to odd sizes. Disaster will follow if you do. (Actually, I'd be surprised if a machine shop would even do it).

[tel76]

Place both shells inside the rod and cap, tighten the two nuts, drill from the outside, remove the shells and chamfer the inside hole just like the other shells are.
Go very carefully, take your time when the drill is about to go through.
I would suggest a countersink drill to chamfer the hole in the white metal and do it by hand, you can purchase these drills locally.
 I have a special cutter that was used for just this job when con-rods were re-metalled.

[Benz Dr.]

Don't do this!!!!!! The extra oil hole seen on some 280SL connecting rods should be left closed. MB found that some these engines drank oil and a lot of them were replaced under warranty. Leave the hole closed - Mike at Metrics told me about this and I have no reason not to believe it.   

[tel76]

Dan,
Can I respectfully ask you to read the all the post's again.
All the shells fitted into the con-rod(not the cap) should have the hole that supplies oil to the thrust side of the piston, the  2nd oil hole that caused the consumption problem was on the non thrust side and should be blanked of, hence all the later bearings were supplied with only one hole in the shell .
I may have misunderstood your post but to suggest that both holes are blanked off is not correct.

[Benz Dr.]

From what I can remember the cap doesn't have any oil holes. Some connecting rods have only one hole, some have two, and very few have three.
I had a set of rods with two holes and rod bearings with only one hole so I called Mike about it and he told me not to drill the second hole due to oil consumption problems. I didn't ask about the rare three hole version but I suspect the answer would be the same.

[tel76]

Dan,
I have re-read all the posts above and at no stage was there a suggestion that the caps have an oil hole.
The early con-rods had two holes, these were deleted when the high oil consumption problem arose, later one's were fitted with only one hole, all new bearings supplied have only one hole.
THE CAP DOE'S NOT HAVE AN OIL HOLE.

[Benz Dr.]

 I had a set of rods with two holes and so I asked Mike at Metrics, someone who should know this stuff, if I should drill the extra hole in the bearing so it could spray oil on the cylinder wall.  He told me no and that MB realized they had made a mistake because new engines, 40 years ago, were consuming a lot of oil. Most of these engines were replaced a long time ago by MB but there are still enough of them around to create some confusion. We sometimes call them bearing caps or caps for short but I know the difference between bearing caps and rod caps - I'm not confused about that. I did say that bearing caps don't have holes which is not correct but that's not what I meant to say at the time. However, you are suggesting that the second hole should be left in place in one post and that they were deleted because of high oil consumption in another post so I'm not sure which one you are advocating. I would call Mike and ask him. 

Actually, I am confused.  Not by what I know; mostly by this strange thread.   

[tel76]

You are confused, everything was under control until you woke up from your slumbers to complicate the issue.
Please highlight on my posts where I have made contradictory statements.
I do realise that there is a difference between UK and Canadian terminology but I have never heard of a bearing shell being called a bearing cap.
I do not need to call Mike as I already know the answer and I would have thought with all your so called experience you would.

[Benz Dr.]

As a matter of fairness to bongo, I would suggest that he believe neither of us and that he call Mike at Metrix or MB and get the exact answer he needs. 

[stickandrudderman]

One of the reasons I continue to frequent this forum above others is the gentlemanly conduct. Please let it continue.