[Mr. P-Body]

Guys... Guys...

Too much debate over a engineering issue... For assembly purposes, it's really quite simple.

First, both the rod and the piston are "offset". That is, the center of the rod, in relation to the bores, is off jut a bit, to the INSIDE. That makes the chamfers opposite on each rod per journal. The piston pin is offset to the non-thrust side, to reduce thrust force during reciprocation.

The purpose of the chamfer and offset, is to allow the oil to escape the rod bearing. The rods are chamfered, stock. When resized, the chamfer is "re-cut". Sometimes, the machinist can get a little over exhuberent, chamfering both sides equally. You MUST use the tangs as a reference. The tang "locates" the bearing, which is also offset in the housing bore.

If you look at a Pontiac block, you will notice it is more like a Ford than any GM engine. It's "laid out" like the Ford (furthest cylinder forward is on the right, not the left), but numbered like GM. Some Ford engines also have the "tangs in".

Yes, Speed Pro (TRW) pistons have 4 reliefs. They also are marked "front", to put the offset in the right direction. Pistons with only two reliefs ALWAYS have the reliefs toward the top, and have no offset. With the two-relief pistons, the bearing tangs line up with the reliefs.

All in all, it simply isn't as complex as some are trying to make it.

FWIW

Jim