this is an old thread, however I'm compelled to reply:
If you have 1958-62 forged Pontiac rods that were shot peened, magged, heat treated to 32 Rockwell SD455 spec, then rebuilt with new ARP bolts, resized big end, they should run to 6500rpm and handle 600HP, in a NATURALLY ASPIRATED application with true 116 octane racing fuel. If they don't then something was done wrong, most likely the heat treating. Or inferior rod bolts.
SD455 rods 8640 steel
- At a hardness of 32 Rockwell C (HRC), the estimated ultimate tensile strength (UTS) for 8640 steel is approximately
150,000 psi (1,034 MPa).
1958-62 rods 1140 steel - At a Rockwell C hardness of 32 (32 HRC), the tensile strength of 1140 steel is approximately 1,030 MPa (150,000 psi)
so basically what you can do with an SD455 rod, you can do within a knat's lash with a well prepped 1958-62 rod. The better material in the SD455 rod will give a slightly higher redline, HP safety factor, longevity.
the primary test for connecting rod strength is tensile strength. It goes up with hardness test rating. i.e. if you take a 58-62 rod heat treat it from 17 Rockwell to 32 Rockwell, that's basically 2x the tensile strength. the key is HOW it was heat treated, and HOW it was quenched. It should be brought up to temperature equalized, then raised in temperature heat treated, then quenched in warm 125 degree OIL- not water. then it should be heat TEMPERED at a lower heat afterward, then allowed to air cool naturally.
I'd wager Vegas house odds the stories of these rods grenading after heat treating were not heat treated and quenched properly, hit with power adders, stroker cranks (BIG difference, longer stroke=easier breakage), or were run into detonation that would grenade any rod. For a 400-428-455 stock block/crank Pontiac there should be no problems NA up to 600hp/6800 rpm.
the cheap Chinese rods aren't the pushbutton answer. 2 years ago my friend's stock rebuild hopped up cam/intake/carb w/headers 428, D-ports, GM block/crank broke a Chinese rod, through the side of the block, destroying everything.
just prior to that my other friend bent a Chinese rod in a 455 Olds with aluminum heads, street build. All top nothing parts, that was an expensive build. Still broke a Chinese rod.
if an engine is over-revved beyond the tensile strength of the rods, or run into detonation with insufficient octane/too high compression, you can break ANY ROD. Power adders that run hot/excessive boost i.e. turbo, blower, NOS, can break ANY rod if they go lean from a fuel problem. NOS has put more stock block Pontiacs on the scrap pile full of big holes, than everything else put together.
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