The OHC Pontiac I-6 is a real mystery motor. I've personally torn down a half-a-dozen cammers and found only one with a set of the "good rods". But they are good. My machinist says they are modest-good quality forged steel, SAE 1030 - 1050?
ARMASTEEL was used because it could be cast not forged and had enough strength to pass muster as cast. Look at a bunch of rods for narrow parting lines or wide lines. Then check out which rods went into LowPerf or HiPerf engines.
Remember the SD455 Poncho V-8 with the HD rods? Rumor had it that they were ARMASTEEL also. But I doubt it. If Pontiac went to the trouble to make a stronger 455 rod why would they ask for trouble by using a LoPerf design.
