Rod bolt swap
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Rod bolt swap

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    Senior Member Ronboats's Avatar
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    Default Rod bolt swap

    I'm putting together a budget 496 BBC and the rods I bought didnt come with ARP bolts as expected.They are 8740 material,but I dont trust them.
    My question is will changing the rod bolts to ARP affect the balance of the assembly if they are not exactly the same weight?
    Or are most bolts 8740 pretty much the same weight?
    Last edited by Ronboats; 09-03-2012 at 11:14 AM.

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    Senior Member EVILFORCE's Avatar
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    In balancing the rods bolts are concidered in the calculations. A good balance job takes things down to less then a gram. So yes bolts could change the balance. I doubt they weigh the same. Will you notice a difference? Doubt it but if you are turning lots of rpm it might show up later.
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    Default Procomp??

    Quote Originally Posted by Ronboats View Post
    I'm putting together a budget 496 BBC and the rods I bought didnt come with ARP bolts as expected.They are 8740 material,but I dont trust them.
    My question is will changing the rod bolts to ARP affect the balance of the assembly if they are not exactly the same weight?
    Or are most bolts 8740 pretty much the same weight?
    Are they Procomp??? I have a set of rods for a SBC that the owner supplied, and they too, have just "8740" on them without a brand name. Procomp DOES sell fasteners, and lists the PSI strengths similar to ARPs. I really doubt the quality compares to ARP, but then again we used the stockers for decades with more successes than failures..... I'm going to use them in the 377 build.....
    Ray
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    Senior Member Ronboats's Avatar
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    I was hoping since there is a rod journal opposite each journal,and they are spinning with the crank rather than reciprocating,they might balance each other out.I'll probably just use the bolts that came with the rods.They must be stronger than the stock rod bolts on the stock rods that were in the motor before the rebuild.

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    Senior Member Ronboats's Avatar
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    Quote Originally Posted by Moneypit View Post
    Are they Procomp??? I have a set of rods for a SBC that the owner supplied, and they too, have just "8740" on them without a brand name. Procomp DOES sell fasteners, and lists the PSI strengths similar to ARPs. I really doubt the quality compares to ARP, but then again we used the stockers for decades with more successes than failures..... I'm going to use them in the 377 build.....
    Ray
    I wasn't going to admit they were Procomp,but,yes they are and as you stated,they just say 8740 on them.If I had ordered the kit with the cast crank,it would have come with eagle rods and arp bolts-I "upgraded" to the forged crank kit and didnt know procomps came with this kit and eagles were an extra cost,as I was told by the first guy I talked to that the only difference in the kits was the crank.I gathered up my pennies and called to order it, and all of a sudden everything was different-

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    Default Better than ????

    Quote Originally Posted by Ronboats View Post
    I wasn't going to admit they were Procomp,but,yes they are and as you stated,they just say 8740 on them.If I had ordered the kit with the cast crank,it would have come with eagle rods and arp bolts-I "upgraded" to the forged crank kit and didnt know procomps came with this kit and eagles were an extra cost,as I was told by the first guy I talked to that the only difference in the kits was the crank.I gathered up my pennies and called to order it, and all of a sudden everything was different-
    As you stated, IMO, you're still better than the stockers...Rods, or bolts, or both.... If you think about it, the bolts see the most stress when being pulled, like, if the plug doesn't fire and the piston is jerked down....Otherwise, the stress is on the top side of the crank and the main section of rod, not the cap... Are $150.-$250. each rods better? Certainly.... But where do we draw the line for our toys? I looked the Procomps for the 377 over real well, and couldn't "see" any issues..... (No Bob, I didn't have my xray vision working, just looked for obvious flaws).... I would caution the use of a "rev limiter", depending on how it limits RPMs it could create a "pull" on the rod, instead of a push...
    Ray
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    Senior Member Ronboats's Avatar
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    Quote Originally Posted by Moneypit View Post
    As you stated, IMO, you're still better than the stockers...Rods, or bolts, or both.... If you think about it, the bolts see the most stress when being pulled, like, if the plug doesn't fire and the piston is jerked down....Otherwise, the stress is on the top side of the crank and the main section of rod, not the cap... Are $150.-$250. each rods better? Certainly.... But where do we draw the line for our toys? I looked the Procomps for the 377 over real well, and couldn't "see" any issues..... (No Bob, I didn't have my xray vision working, just looked for obvious flaws).... I would caution the use of a "rev limiter", depending on how it limits RPMs it could create a "pull" on the rod, instead of a push...
    Ray
    Well,about the x-ray vision....

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    Pro Comp BBC 6.135" H - Beam Connecting Rods - Item # PC 41252
    Procomp BBC Big Block Chevy Large Journal "H" beam street/strip connecting rods are manufactured from aircraft quality 4340 chromoly steel. The rods are x-rayed and ultrasonically tested with all surfaces shot peened and stress relived. Perfect for big block engines producing 800+ HP. All the big block Chevrolet’s use 0.990" piston pin.

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    Ain't Right Racin piston in the wind's Avatar
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    After changing the bolts the rods shoud be checked for roundness. Due to the better bolt having a stronger clamping force causing the big end to go oval.

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    Default Another....

    Quote Originally Posted by piston in the wind View Post
    After changing the bolts the rods shoud be checked for roundness. Due to the better bolt having a stronger clamping force causing the big end to go oval.
    Another reason to "run 'em" in my mind.... Hell, we built all sorts of stuff with the stockers for years...Surely these Procomp rods and bolts are better than the stockers of the 60s-70s....I'm sure there will be some naysayers, but the first sentence of the OP does say "budget"....
    Ray
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    Quote Originally Posted by Moneypit View Post
    .... If you think about it, the bolts see the most stress when being pulled, like, if the plug doesn't fire and the piston is jerked down..
    Ray
    If you REALLY think about it, It happens 4 times in the engine, every revolution. 50 times a second to each rod at 6000 rpm. Its called the intake stroke. Auto shop 101.


    The bolt is made in the same place the rod was. They MAY be a reason EVERY respected rod "manufacture/seller" doesn't use the bolts made elsewhere, and pops the extra coin for an ARP bolt.
    Think about it, Scat, Eagle, Manley, Engine Pro, Lunati, all sell rods manufactured in China, but they ALL use rod bolts(by far the most highly stressed part in the entire engine) made here. MMMmmmm



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    Last edited by gn7; 09-03-2012 at 05:47 PM.

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    Default Of course it does...

    Quote Originally Posted by gn7 View Post
    If you REALLY think about it, It happens 4 times in the engine, every revolution. 50 times a second to each rod at 6000 rpm. Its called the intake stroke. Auto shop 101.


    The bolt is made in the same place the rod was. They MAY be a reason EVERY respected rod "manufacture/seller" doesn't use the bolts made elsewhere, and pops the extra coin for an ARP bolt.
    Think about it, Scat, Eagle, Manley, Engine Pro, Lunati, all sell rods manufactured in China, but they ALL use rod bolts(by far the most highly stressed part in the entire engine) made here. MMMmmmm
    last time I checked there was an open valve during the INTAKE stroke. That's not quite the same as trying to pull a piston against a tight "vacuum" at the top of the cylinder... While i agree the ARPs are a better choice, he's up against choice #1, send them back, get the ARPs, re hone the big end, and re balance to the ARPs, choice #2, use what he has...#3, send them back and get the Eagles w/ the ARPs installed, re balance, and eat less for a few weeks....
    Not really sure what I would do, but if it's a recreational boat I think I'd run what I have on hand...
    Ray
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    Quote Originally Posted by Ronboats View Post
    I'm putting together a budget 496 BBC and the rods I bought didnt come with ARP bolts as expected.They are 8740 material,but I dont trust them.
    My question is will changing the rod bolts to ARP affect the balance of the assembly if they are not exactly the same weight?
    Or are most bolts 8740 pretty much the same weight?
    No

  15. #13
    steelcomp was here
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    Counterfeit bolts have ZERO reliability. They have to meet ZERO standards and go through ZERO testing. They could be grade 5 and you'd never know it. Just becasue they torque up to spec means nothing about what has happened ot the metal.
    Now, I will say, if there was a huge rash of engines with broken rod bolts linked to Pro Comp rods, we'd hear about it so they're probably OK, but for peace of mind, I'd get the ARP 8740's and be done with it. The weight will be absolutely insignificant. If the other bolts are even close to "real" 8740, then the rods will most likely stay the same shape...which is not to say they were round to start with. Highly unlikely, being what they are. They need to be checked regardless.
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    Senior Member jimclauss's Avatar
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    Quote Originally Posted by EVILFORCE View Post
    In balancing the rods bolts are concidered in the calculations. A good balance job takes things down to less then a gram. So yes bolts could change the balance. I doubt they weigh the same. Will you notice a difference? Doubt it but if you are turning lots of rpm it might show up later.
    what do you consider lots of rpm on a buget 496??? Less than a gram get real.
    Last edited by jimclauss; 09-03-2012 at 07:51 PM.

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