con rods and bearing caps - orientation

[wymlen]

The con rods and bearing caps are stamped on one side with matching numbers and also have an indelible number 1-6 marked on the other side. Is there any particular orientation for the stamped number side (facing the left or right side of the engine)? The pistons have a small arrow indicating position in cylinder is towards the front of the engine so it may be the con rod may have to be repositioned in the piston.
Regards,
Mal.

[ja17]

Hello,

The "electro etched" numbers 1-6 must go on the left side (oil filter side).  It they  also have the stamped numbers, they must be oriented on the other side (manifold side).  All piston arrows point forward.

If yours is a seven main bearing engine, most of the  main engine bearing caps have a sometimes hard to see number cast or stamped in the side. Main bearing caps #1 and #2 are marked in this way.  The cap which holds the thrust bearing, #3  I recall, is not marked, but is uniquely machined on its side for the thrust bearing. #4, #5, #6 main bearing caps are also numbered from the factory. #7 is not. Process of ellimination will identify this bearing cap!

Joe Alexander
Blacklick, Ohio

[Dave Gallon]

Joe is, of course, 100% correct. It is interesting to note that this information is only present (as far as I know) in the Model 190 Workshop Manual (corresponding to the Ponton sedan of the 1950s with 1.9 L four cylinder engine). The manual states, "The connecting rods are numbered 1 to 4, corresponding to the four cylinders. When the pistons, with connecting rods attached, are correctly installed the numbers on the connecting rods must be on the left side, and the arrow on the piston-head must point in the direction of travel."

[wymlen]

Joe, Dave.
Many thanks for reply. As you say Dave, there appears to be no specific reference in Mercedes manuals, Autopress manual refers to 'numbered side to left side of engine' but doesn't say stamped or etched numbers. I believe it is relevant as it must match the original assembly when engine was dynamically balanced.
Mal.

[ja17]

Yes, as I once said before, Mercedes Workshop Manuals are like "Soap Operas" you have to see the previous episode to understand everything.

The orientation of the connecting rod is critical since oil holes in the rods direct lubrication to engine parts at critcial times. Reversing the rods will result in catastrophic eninge failure.

[al_lieffring]

The factory markings may not always be visible or could be tampered with, I was taught to install the rods and caps with the bearing index tap facing toward the oil filter side of the block. Because when working on the engine it is upside down and left and right can be confusing.

[Benz Dr.]

You can take Al's description as 100% correct. The small notch for the rod bearings always goes to the oil filter or distributor side of the engine. Generally speaking, the left side. It is the ONLY method I use.