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1980 Chevy Monza notchback; 350 5 speed
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Discussion Starter · #1 · (Edited)
Hey all, I have a '76 L82 350 out of a 'Vette and at first my machinist and I both thought the rods were old "O" rods, but I took a closer look and the casting is clearly a "D". Not only that, but only 6 are like that, the 7th is an "X" rod and the eighth I can't make the casting out. Anybody know what might be going on here or what these "D" rods are about? I know the engine was rebuilt.
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1980 Chevy Monza notchback; 350 5 speed
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Discussion Starter · #5 ·
Look at the Scat ICR5700---4340 with capscrews
That doesn't answer my question, nor is this helping me. I know there are other rods, but what I want to know is if these will handle up to 500 horse. If you don't know, then please don't give anymore useless replies. I can't find any information on these at all, which is what I'm looking for, not misdirection.
 

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The “D” is nothing more that an identifier for the die that was used to forge that and probably thousands more. Look at the long shank if it has been flash ground smooth and shot peeled with 7/16th bolts your on to something special though probably well along in its fatigue life.

The production L82 got “pink” rods, these are production mild steel 1046 or 1053. These were shot penned but use the 3/8ths bolt unless some shop did some custom work.

I rather think based on expensive experience that the factory bolt and nut rods short of some speciality Bowtie 4340 forgings I would agree with Imsport that expecting these to hold up to 500 horses is a “Bridge to Far”. I mean it’s a crap shoot at best and one where your betting the entire engine and all the money that is contained therein for parts and services.

Rods are the highest loaded item in the engine and are high on the structural failure list. The bolt connection is one of the most common failure points and much of that has to do with the mated section design outboard of the bolt. The high loads at high power and RPM are stretching the cap in the downward direction. This is trying to open mate of the bolted parts from the inside. The bolt is put in shear bending which is the weakest direction for strength. The load is transferred to the out board pad which is usually too small on GM rods. The inside of the joint cracks open pinching an edge of the bearing into the journal. When this happens the bearing exposed edge squeegees the oil off the crank, the journal and bearing overheat and weld together and the rest is junkyard history.

Best advice these days is new rods with modern ARP cap bolts into the shank (no nuts) and with locating dowels a ring the bolt to help pick up the shear bending load from the bolt shank and spread it over more area, in other words increase the load carrying capability that is resisting the cap pinching the bearing into its journal. For desired your power level this would be my minimum choice rather than use some mixed batch of old rods for which I have no history.

Scat 25700716: Pro Series I-Beam Connecting Rods Small Block Chevy - JEGS High Performance

But while I’m willing to bet with my life, I try not to with my engines.

Bogie
 

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More for Less Racer
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21,106 Posts
By the time you buy the new ARP rod bolts, have them replaced, and have the rods shot-peened and resized so that they might handle 500hp you will have spent the money that could have bought the better material (4340 chromemoly) SCAT capscrew connecting rod that has zero cycles on it.

It really isn't worth rebuilding stock rods anymore.

Lmsport gave you good advice.....check the stock rod beams for width.....any that are skinny on width means the weight is all in the balance pads and the rod beam is weaker......doesn't matter if it has "X" , "O", "D", or whatever.
Stock rods are just plain 1053 Mild Steel.....even those once famous "pink" rods are nothing more than a x-rayed and shot peened stock rod.

Even the Eagle SIR I-beam, 5140 material, would be a step up from the stock rod.
 

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1980 Chevy Monza notchback; 350 5 speed
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7 Posts
Discussion Starter · #8 ·
The “D” is nothing more that an identifier for the die that was used to forge that and probably thousands more. Look at the long shank if it has been flash ground smooth and shot peeled with 7/16th bolts your on to something special though probably well along in its fatigue life.

The production L82 got “pink” rods, these are production mild steel 1046 or 1053. These were shot penned but use the 3/8ths bolt unless some shop did some custom work.

I rather think based on expensive experience that the factory bolt and nut rods short of some speciality Bowtie 4340 forgings I would agree with Imsport that expecting these to hold up to 500 horses is a “Bridge to Far”. I mean it’s a crap shoot at best and one where your betting the entire engine and all the money that is contained therein for parts and services.

Rods are the highest loaded item in the engine and are high on the structural failure list. The bolt connection is one of the most common failure points and much of that has to do with the mated section design outboard of the bolt. The high loads at high power and RPM are stretching the cap in the downward direction. This is trying to open mate of the bolted parts from the inside. The bolt is put in shear bending which is the weakest direction for strength. The load is transferred to the out board pad which is usually too small on GM rods. The inside of the joint cracks open pinching an edge of the bearing into the journal. When this happens the bearing exposed edge squeegees the oil off the crank, the journal and bearing overheat and weld together and the rest is junkyard history.

Best advice these days is new rods with modern ARP cap bolts into the shank (no nuts) and with locating dowels a ring the bolt to help pick up the shear bending load from the bolt shank and spread it over more area, in other words increase the load carrying capability that is resisting the cap pinching the bearing into its journal. For desired your power level this would be my minimum choice rather than use some mixed batch of old rods for which I have no history.

Scat 25700716: Pro Series I-Beam Connecting Rods Small Block Chevy - JEGS High Performance

But while I’m willing to bet with my life, I try not to with my engines.

Bogie
That was what I wanted to know. ARP bolts were already in the plans IF they were worth working with, which is what I was trying to find out. I know about the "O" rods and the "X" rods being sought after as well, but considering I didn't know jack about these and there wasn't any information readily available on Google I figured I'd ask. Hell, you never know what you can come across these days. Thank you for the info.
 

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That doesn't answer my question, nor is this helping me. I know there are other rods, but what I want to know is if these will handle up to 500 horse. If you don't know, then please don't give anymore useless replies. I can't find any information on these at all, which is what I'm looking for, not misdirection.
I gave the short, correct, answer. Go waste space on another forum with your trivia questions.
 

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Race it, Don't rice it!
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Imsport and Eric have you going in the right direction. Stock rods aren't worth even looking at UNLESS it's a stocker rebuild and even then its iffy because of the time involved to get them round and straight. There isn't a GM rod that is better than Scat or Eagle stock replacement rod. Period. Same money, better everywhere.
 
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