Downunder,
the plot thickens on the Irvine .61 engines and the connecting rods.
I found my other Irvine .61 engine. For some odd reason it was in a old Moki engine box, and I was wondering where and when I had obtained a Moki, so I opened it up, and there was the missing .61 engine. This one has a real Irvine carb on it too. But when I removed the backplate to check the connecting rod orientation, I found the rod was different and it didn't have a logo on it either. Also the crankshaft is somewhat different in that it has a round shape with cutouts in the rear portion whereas the engine I tore apart and rebuilt has a "D" shape rear portion on the crank.
So I wonder which engine was made first. I would think that the one with the CNC machined connecting rod, that is this engine, was a later model versus the engine I rebuilt that used a cast crankshaft was a earlier model.
So it looks like the hole that was drilled in the crankshaft big end should face towards the front of the engine. Of course getting into technical stuff, what advantage is there to having the lubricating hole on the big end of the rod facing forward versus facing to the rear. Does it improve lubrication? Or does it even matter? it isn't just Irvine engines, I have seen this on numerous other brand engines too.
The other Irvine 61 engine I have:
Here is the connecting rod in this engine and the different shape crankshaft:
The crankshaft from the engine I tore apart and rebuilt.
