Oliver 550 Connecting Rod Orientation

r8f1k

Member
Let me preface by saying I know that I made a mistake by not marking my pistons to indicate the original direction. I did number the rods and caps. (3.625 BORE, 2.25 MAINS, 2.25 RODS) I removed my pistons on a Waukesha 155 a few weeks ago, did all the engine work and when I was ready to reassemble, there were no piston marks to indicate forward. Nothing on the piston heads, rods, etc. On all of the rods there is a part number on one side and a "DX" on the other. When I put the first piston (No. 3) in, it would not go in with the "DX" forward as I thought that might indicate. It would hit one of the crank weights going in. So I flipped it.
I installed (No. 2) next and the same thing happened. It SEEMS like the pistons are slightly biased to prevent them from going in wrong. IS THIS TRUE? Am I just screwing this up or is that the case?
I have all the pistons back in, in what seems the right locations, engine turns nice, no binding, no scratching, etc. ANY FEEDBACK WOULD BE GREAT!!! I am a high school shop teacher and my students always want to keep moving. I am hesitant to remove from the engine stand and reinstall before I get a good answer. PLEASE ADVISE.
 
The usual convention for all engines is to mark bearing caps to avoid any accidental swapping. These are usually indexed from timing end (front) and marked on the timing side to avoid being fitted back to front. Matching marks are made on each of the rods, so the marks go together on re-assembly.

V engines may have a different cylinder numbering system. Overhead cam engines might present a further difficulty, too.

Clearly those marks would provide rod orientation even though not needed if they only fit in one hole, but it avoids some mismatching possibilities.
 
It has been too many years. The pistons (at least O E piston) go in either way. The rods are offset and 2 go in one way and 2 the other way The close part of the offset goes next to the main bearing. I can mail you a picture.
 
I know that I have the caps on the rods correctly. I was assuming (stupidly) that once I pulled the pistons and cleaned them up, I would find a mark on top of the pistons to indicate forward. Alas, I did not. They do in fact fit in where 2 go one way and 2 go the other. There are old marks "57" and "42" on the rods and caps which would seem to indicate cap alignment. Then there are also my own 1, 2, 3, 4.
It seems to be correct, just wanted to make sure.
 
The rods in that motor need to be installed in 2 different ways. Number 1 and 3 face the same direction and Number 2 and 4 face the Same direction but opposite of the other two. If you get them in right the rods should be centered in the piston one you have all the caps on. Consult a shop manual but off the top of my head I think it?s that Number 1 and 3 have the long part of the offset facing back and Number 2 and 4 it faces forward.
 

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