[Half-Inch Stud]

Originally Posted by Cliff R

.........The introduction of the low cost Eagle (and Eagle knock-offs/clone) "H" beam rods pretty much obsoleted any EARLY factory offerings, even the better "EARLY" Super Duty rods.......Cliff

Fixed it for ya.

73-SD rods surely remain an excellent Reliable 455 rod.

And them 5140 rods sure are an economical solution.

[AC445]

Hello,I agree with 1/2" on 485225 SD rods.I also ran 529238 early SD rods in the 60's and early 70's and never lost one even with the old heavy pistons.I bought 2 NOS 529238 spares just in case and they're still on a shelf in my garage.Now the H beams are a good choice.

[tanksteve]

Gavin, that was a nostalgic experiment. I remember those early hot rod guides and their recommendations to get the early forged rods and heat treat them. I cant imagine how many engine failures resulted from doing that. Probably almost as many failures as Pontiac's nylon toothed camshaft gear. Those early guides didnt understand that even if you got a decent Rockwell hardness on the outside of the rod, it wont go deep on what is basically plain carbon steel with a little bit of manganese.

But we had so few choices back then for good rods. Now we can use the Chinese alloy steel rods and not worry. And it amazes me that these Chinese rods are holding up. There must be quality control on the production of those rods that is absent on almost everything else made in China.

[Cliff R]

+2

We are blessed that the "H" beam rods are excellent parts, but I wouldn't touch a Chinese cast steel crank with a 10' pole! For the extra cost get the forging, even for your "street" engine build.....FWIW......Cliff

[steve25]

X2, I would do my best to turn up a factory crank even if it was cut .020" already as compared to cast off shore crank!
Years ago when I built my super charged 455 I had the crank cut to .030" under even though I could have run it with just a polish, and that motor is pumping out 650 hp .

[mgarblik]

As much as it pains me to admit it, the Chinese connecting rods are a better choice in every case I can think of than 1958-62 production rods. I remember clearly paying $200.00 a set for the old rods and also scouring the junk yards looking for 58-62 Pontiacs for the sole purpose of extracting the rods. Those were the days. Personally never had a failure of those old rods using them without heat treatment. But the highest HP application for me was around 415-425 HP. in a 66 2+2 stick shift car @ 6000 RPM's. I guess I was lucky. Very careful prep and ARP fasteners likely kept them in 1 piece. With the Chinese rods, all of them require the careful prep work. Taking them out of the rice paper and putting them directly in the engine is almost a guaranteed failure.

[hurryinhoosier62]

Originally Posted by mgarblik

As much as it pains me to admit it, the Chinese connecting rods are a better choice in every case I can think of than 1958-62 production rods. I remember clearly paying $200.00 a set for the old rods and also scouring the junk yards looking for 58-62 Pontiacs for the sole purpose of extracting the rods. Those were the days. Personally never had a failure of those old rods using them without heat treatment. But the highest HP application for me was around 415-425 HP. in a 66 2+2 stick shift car @ 6000 RPM's. I guess I was lucky. Very careful prep and ARP fasteners likely kept them in 1 piece. With the Chinese rods, all of them require the careful prep work. Taking them out of the rice paper and putting them directly in the engine is almost a guaranteed failure.

Agreed, Mike. NEVER assume a part is "good" simply because it's new. I've seen Carrillo rods that were "tight" in the pin bore bushings. ALWAYS check a part before installing it. It will save you time and money in the long run.

[Jack Gifford]

Originally Posted by flat-bill

... Are the '56 rods any better?...

'55-'57 rods are castings.

I notice that HO Racing's chart gives engine speeds at which each rod/stroke combination will provide a 2:1 safety factor. For instance, at 3.563" stroke the '58-62 forgings are "safe" to 6,458 RPM. My experience showed that the safety factor DOES apply. For about three seasons of mini-rod pulling (dozens of events per year) I ran an alcohol injected 381 c.i. with '58 rods (hung, aligned, resized, and ARP bolts), usually to 7,200 RPM (I'm guessing about 425 HP) without a single rod failure.

Ponder this: every aluminum rod out there is "rubbery" compared to its steel equivalent...

[steve25]

Yes, but most times a Aluminum Rod will stretch , go out of round and bite a Bearing before it just snaps and this maylay is found before the next run.

If early forged rods used with sanity in race use where changed out on the time frame recommended for Alumnium rods then there may be a good amount less failures seen with those too, not that I think anyone should use these Rods these days but for a street rebuild on motors of less than a 4.00" stroke!

Of notability on these early Rods they do have the plus of being a good amount lighter than the cast rods, so the rev's come up faster which in and of itself adds to performance.

[flat-bill]

Thanks for the info on the '56 rods. All good tips and something for me to think about. Billk

[GTO-relic]

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.

[mysticmissle]

i agree, my experience with early forged rods was fine. it was short and not more than 430 hp or so. i also never hurt a cast rod motor that ran in the deep 10s at less then 5800 rpm. I did blow an eagle rod to smithereens trying to make a 12 second combo run 11s. in an rpm the motor wasn't set up for, even though it had decent rods. I believe the main spun, starved the rod(s), popped a rod bolt. snapped the rod in the middle, rotating rod section took out a nice 455 block. oddly there was no big kaboom, just a decent bang and then mostly silence as car rolled to a stop. friction and lack of oil are not to be messed with

[steve25]

You can’t just gloss over the G load factor a rod had to deal with as the stroke increases.

A perfect factory 55 to 62 ( non SD ) forged rod heat treated to 32 might live for a full 4 seasons of drag racing at 6500 with a 4.00” stroke swinging it from stop to start, yet fail just in just 5 passes down the 1/4 mile with a 4.210” stroke.

[GTO-relic]

To heat treat 1140 steel to 32 Rockwell hardness, you must first austenitize it by heating it to 1500-1550 degree F., and then quench it rapidly in oil. After it has cooled, temper the steel by heating it to 400-1200 degrees, holding it for at least 15 minutes per inch of thickness. The exact tempering temperature depends on the desired hardness within that range, so some experimentation may be needed to fine-tune the final hardness to 32 Rockwell C.*

I had 2 sets 1958-62 heat treated, then they hardness tested top, middle, bottom ON ALL 16 RODS. it was same throughout. some rods were higher than others, all were 31-34 Rockwell. the posts staying it only hardens the surface are misleading, they are getting CASE HARDENING confused with true HEAT TREATING, whereas the material in the latter is the same hardness throughout depth. Quenching in oil with draw carbon into the rod as well. some shops mistakenly quench in water, or don't temper. those are the problem rods.

[GTO-relic]

even the 1963-66 421 HO rods can be heat treated to 32 Rockwell to improve their strength, durability. the reason there was problems with those rods is, they were 1137 steel and not heat treated, and put in 421HO engines with the longer 4" stroke, stressing the rods more. the 1958-62 rods never saw a stroke longer than the 3.75" of the 389. a rod that will last forever in a short stroke engine, may break in a week in a long stroke engine, especially if it's NOT HEAT TREATED AT ALL- like the 1958-62 and 1963-66 HO rods.

Carbon content: As a resulfurized carbon steel, 1137 has a carbon content of 0.32–0.39%. Steels with higher carbon content are more responsive to heat treatment for hardening.
Manganese content: With a manganese content of 1.35–1.65%, the hardenability of 1137 steel is improved, meaning it can be hardened more effectively than plain carbon steels with similar carbon content.
Free-machining properties: The added sulfur in 1137 steel improves its machinability but makes it unsuitable for welding and somewhat reduces its toughness compared to equivalent carbon steels.
Tempering: Achieving exactly 32 HRC will depend on the specific tempering temperature used after the initial quench. Higher tempering temperatures will result in a lower hardness, while lower temperatures will result in higher hardness

[GOAT8U2]

Gavin, I don't you mentioned who did the vacuum heat treating, you personally or did you send it to a company?

Which company?

If you sent out, what do they charge per rod?

Heat treatment to remove some austenite, then cryo to strengthen even further might be the best solution if you wanna run the older rods.

[GTO-relic]

ROD RPM LIMITS are based primary on TENSILE STRENGTH, the primary inputs being material/hardness of rods, stroke length, mass of the rod w/piston combined.

RPM LIMIT = SQUARE ROOT OF: strength / (weight x stroke x internal loading factor x 2)

meaning....increase the material hardness increases the tensile strength, increases the rpm limit
increase the weight of rod or stroke length decreases the rpm limit.
2 is the constant factor of safety. internal loading factor is based is based on rod length/stroke.
shorter stroke/longer rod decreases internal loading factor.

doubling the hardness of the material roughly increases the tensile strength- it's proportional

For 1140 steel, a Rockwell C hardness of 32 corresponds to a significantly higher tensile strength than a Rockwell C of 17
. Hardness and tensile strength are directly proportional in steel, meaning as hardness increases, so does tensile strength.
A higher Rockwell C value indicates that the steel has been heat-treated to be stronger and less ductile.
Approximate tensile strength comparison
Using standard conversion charts for carbon steels,
the approximate ultimate tensile strengths are as follows:
1140 Steel @ 17 HRC 1140 Steel @ 34 HRC
Heat Treatment -This higher hardness level is achieved by quenching and tempering the steel, a process that intentionally increases its hardness and strength.
Tensile strength for a 17 Rockwell 1140 steel is approximately 95,000 to 105,000 psi.
Tensile strength for 34 Rockwell 1140 steel is approximately 155,000 to 165,000 psi.

[GTO-relic]

results

[GTO-relic]

ARP bolts,
dimples on face of small end, big end from hardness tester
worth it for what you get
$100 for the cores, $100 for heat treat, $200 for shot peen/mag/resize, $100 for the ARP bolts.
$500 for MADE IN USA rods.
although that was 2019.

[Dragncar]

Originally Posted by GTO-relic

ARP bolts,
dimples on face of small end, big end from hardness tester
worth it for what you get
$100 for the cores, $100 for heat treat, $200 for shot peen/mag/resize, $100 for the ARP bolts.
$500 for MADE IN USA rods.
although that was 2019.

What are we doing here ? This is not 1982.
You can not heat treat mild steel into good steel. And even IF you could those rubber rods are spindly in comparison to the cheapest offshore 5140 steel rods.
450 $, check over and be done with it.
Spend 300 $ more and get a Molnar rod which you will not have to put another dime into and will handle more horsepower than any OEM block can handle.

These engines done right cost FAR too much money not to mention the time it takes to do it all yourself to try and make a rod that was not done right in the first place, right. And it can not be done anyway.
NOS is not the thing that has sent the most of our wonderful Pontiac blocks to the scrap yard. Its trying to race cast garbage rods without a clue.
I watched a racer I knew take a 455 out of the junkyard, knurl the pistons and slap a big cam, headers, T1 and a 750 on and try and race. And laughed when he blew a rod out of the pan so hard it dented the frame.
Fools like that ruined blocks.
Its not the early 80s. Cast rods belong in stock engines. Rubber rods, even heat treated belong in nice numbers matching show cars that do not get driven much.