Mac Rod Offset?

[Dennis Detweiler]

1) The rod bearing opening (big end) looks offset from rod center? Which way does the rod face on the crank?
2) Is the piston (wrist pin opening) offset also? I see no arrows or markings on the piston other than the oversize numbers stamped into the top of it.
Thanks

[Gordon Duax]

It's not supposed to be..........

[Jeff Campbell]

... nope, no offset on Mac rods, of course you may have a defective part, or something that someone specially made/modified. The rods are intended to by symetrical, so the piston can go on the rod either way (but most pistons require being oriented one way in the block). Remember that the big eng rod cap only goes on one way (align the pips), bolting down a rod cap with just light pressure will ruin the rod, as the cap will never align accurately again.

Jeff

[Jack Gesler]

It is common for McCulloch rods to have the small end not on center. The Big ends also are not always exactly symmetrical. What counts is that the diameters, center to center length, and straightness. Below is a photo of the small end of a McC rod that shows that is is not uncommon to have the holes offset. Which way it is assembled does not matter.

[Dennis Detweiler]

Thanks,
What I'm seeing is the large end housing is not symmetrical (one side has a little more mass), but the opening is centered with the rod shaft.

[jmendoza]

Castings are deciving!

[Jeff Campbell]

Here are some drawing details that I have for a few Mac rods. The dimensions show the big end is symetrical relative to casting centerline, and rod bolt hole positions, but as anyone that has worked with cast/forged parts, variations in the castings/forgings can sometimes be much more than the tolerances of the finish machine work and certainly less than ideal.

Jeff