Not to beat a dead horse, but I remember riding in a 62 Catalina as a 7 year old egging my father on watching the speedo as I wanted him to bury it and being disappointed as it only got to 105mph in a convertible with top down. Never an engine problem with that car till he sold it as it got rust somewhere he couldn't get off with Noxon. My 65 Tempest with an early junkyard 389 in it endured in addition to my many missed shifts that buried tach, a fruitcake mechanic that lost his son in a car like mine hold pedal to floor till I pounded on garage door making him stop, I was eating next door, was my graduation day from high school. Threw timing chain next day and he fixed it. Drove for 2 more years .. motor never apart except for that repair. Finally made a trade for a bright orange 72 Chevelle in Cherry Point NC I have always regretted tho the Sanyo quad 8 track I put in sounded beautiful to Robin Trower "Bridge of Sighs".
So what happens when you do that test with a cast iron bolt made of the same material that was used in the majority of rods and crankshafts installed in Pontiac engines from the factory? How many of those experienced crankshaft and rod failures? Most here want a bulletproof drag-race rod and 58-62's don't fill that bill as well as others more readily available .. I get that. I drug out my machinery's handbook for some reference tho ...
Steel is mainly iron + additives to strengthen it. 3 main categories ..
1. Carbon Steel
2. Alloy steel
3. Stainless steels
Iron rods were cast and steel rods were forged, kind of hard to believe an improved material being forced into position would result in a rod with less strength than a lesser one poured into position .. it may be true Im no expert, but believe difference is most likely marginal altho I could not find iron strength numbers.
Early 1140 rods appear to be forged from coarse grained carbon steel that was not heat-treated making it easier to forge them. Also allowing for an improvement in their durability if heat treated by 20-30% at least tensile strength and hardness wise. Possibly more if low temp water-quenched and tempered as they have same characteristic as 1040 steel, at least my novice take from Machinery's Handbook tables. Its kind of like reading the bible tho
If treated correctly it appears the hardness is almost equivalent to 4340 though the tensile strength only reaches 50% of 4340 if it is also quenched and tempered .. 73% of untreated 4340.
Conclusion Ö I wont be afraid to use these rods on a street motor but will heat treat them and upgrade the rod bolts. Would use 4340 on high performance build that might see track time.