cylinder 1/3 offset and 2/4 offset

[theKbStockpiler]

I understand that the wrist pins are offset to load the connecting rod on the crank journal a certain way but why are the 1/3 cylinder set offset towards the cam gear end and the 2/4 cylinders offset towards the flywheel?

[FJCamper]

Hi TheKbStockpiler,

All offsets are the same on both cylinder banks, same orientation, guaranteed by the con rods facing "up" in pairs on both sides and the piston arrows pointing toward the flywheel.

If you have a piston, just for entertainment purposes, get a ruler and square and try and figure out with the piston arrow facing the flywheel, is the wrist-pin hole slightly higher or lower than center?

You're actually asking a very good question. Remember, "I hear and I forget. I look and I remember. I do and I learn."

FJC

[theKbStockpiler]

I can't post an image right now but if you look at a type 1 rod ,the part that the wrist pin is pressed into is not centered on the rod and offsets the piston from either the front of the case or the rear, not up or down.

[FJCamper]

Hi TheKBStockpiler,

Marc, on this forum, gave the best answer to this question way back. I quote him here:

"Wristpin offset in the piston is in relation to the piston centerline ("up" or "down" on our engines), and only in the piston. This is the relevant dimension for the noise and torque concerns. Measure the distance from the wristpin bore to the thrust surfaces of the piston on each side (if it's 1mm different there's a .5mm offset, etc.)
Installing the pistons backwards (arrows facing the oil pump end on an ACVW) creates greater rod angularity at TDC - the rod is already slightly tilted to push the crank over - which boosts power but causes more noise...and where there's noise, there's wear.

The connecting rod offset Berg referred to is fore&aft, to center the small end bushing on the wristpin. Place the rod on its side on a flat surface, then flip it over - if there's an offset it'll be apparent in the distance between the small end and the table when the big end is in full contact."

[theKbStockpiler]

So actually the rod part of a connecting rod IS offset within the boundaries of the big and small end. The piston is not actually offset from being inline with the crank journal. If a type 1 rod is laid on one of it's sides and the distance between the (rod part) is measured from what is it lying on ; and then flipped and measured again ,the distances are different. For some reason the piston is (worked around) from it's direct path.