Polished 12 rods

Thanks you very much. I am in the process if building my engine and that helps a lot
 
Harbor freight has some pretty good deals on them.

Monkey Fist Rage
 
so how much stronger does polishing make the rods? i have some old 1969 and 1970 hot rods magazines and it seemed to be pretty common to polish them (in gas motors) and install good bolts back before aftermarket units were cheap and easily availible .
 
dozerjoe said:
so how much stronger does polishing make the rods? i have some old 1969 and 1970 hot rods magazines and it seemed to be pretty common to polish them (in gas motors) and install good bolts back before aftermarket units were cheap and easily availible .
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Doesn't make them stronger, just relieves stress risers so less likely to crack under stress.


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Thus making them stronger?

Anything that is not nice and smooth in a vibrating part can be a point where waves in the component will converge and the "stress" at that point can be enough to cause the part to fail. By removing those points (sharp edges in most cases) the stress has the ability to "roll" somewhere else in the part and dissipate safely.

As ghostman said, you aren't inherently making the part stronger than it was when it was made, but less likely to fail when is sees a given power level. Which makes it stronger than the flaws allowed it to be. Shot peening works in a similar way by forcing stress made into a part at the factory to relieve. Same with cryo treating.

You aren't making it stronger as much as removing weakness, which makes IT (whatever it may be) stronger.

I just woke up so flamers go easy.

Monkey Fist Rage
 
dozerjoe said:
so how much stronger does polishing make the rods? i have some old 1969 and 1970 hot rods magazines and it seemed to be pretty common to polish them (in gas motors) and install good bolts back before aftermarket units were cheap and easily availible .
Click to expand...

This is where i learned when I was a teen in the 90s, reading old magazines. It didnt make sense then.

Monkey Fist Rage
 
biggy238 said:
Thus making them stronger?

Anything that is not nice and smooth in a vibrating part can be a point where waves in the component will converge and the "stress" at that point can be enough to cause the part to fail. By removing those points (sharp edges in most cases) the stress has the ability to "roll" somewhere else in the part and dissipate safely.

As ghostman said, you aren't inherently making the part stronger than it was when it was made, but less likely to fail when is sees a given power level. Which makes it stronger than the flaws allowed it to be. Shot peening works in a similar way by forcing stress made into a part at the factory to relieve. Same with cryo treating.

You aren't making it stronger as much as removing weakness, which makes IT (whatever it may be) stronger.

I just woke up so flamers go easy.

Monkey Fist Rage
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This is the best explanation I have heard as of yet. Dumbed it down enough to where even I could understand why. Question now is, what power levels are we talking about before something like this is truly beneficial? Or is this a high RPM thing?
 
rockytopcummins said:
This is the best explanation I have heard as of yet. Dumbed it down enough to where even I could understand why. Question now is, what power levels are we talking about before something like this is truly beneficial? Or is this a high RPM thing?
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In all honesty it depends on an individual component.

A bad machined radius (corner instead of radius) can make a rotating part fail under its intended use. For example, where an input shaft meets the drum needs a radius and not a sharp corner.

Its easier to point out in a failed part.

I would look at it less as a power adder in maximum effort and more as a way to increase duty cycle in a maximum effort engine.

I know there are guys much better versed in failure analysis than i am. Wish they would chime in.

Monkey Fist Rage
 
Look up a guy by the name of Ed Pink. He was one of the original innovators in grinding and shot peening rods. Or as us old bastages call these rods Pink Rods.
 
rockytopcummins said:
This is the best explanation I have heard as of yet. Dumbed it down enough to where even I could understand why. Question now is, what power levels are we talking about before something like this is truly beneficial? Or is this a high RPM thing?
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He doesn't need his head made any larger.
 
A lot of machine shops will magnflux the rods as well to make sure there is no cracks that are unseen to the naked eye.

A good video showing you the basic idea behind magnflux testing.


[ame="http://www.youtube.com/watch?v=qpgcD5k1494"]http://www.youtube.com/watch?v=qpgcD5k1494[/ame]
 
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For those that might not understand the purpose behind the polish and shot peening. The connecting rod sees compression and pulling forces. You want to polish the rod to remove possible stress risers. A stress riser is basically any sharp formation in the material. The sharp valley's of the peaks are what you want to eliminate. Once you eliminate those some and most come back and shot peen the surface. The small smooth dimples that the shot crates forms compressions in the material. (Similar to case harding) Add magna flux stronger rod bolts to the procedure you have done all you can do to ensure you have a set of good rods. (Some folks will and cryo-treatment to help relieve internal stresses.) As for wicking oil away from the rod. I personally believe that the diesel engines don't turn enough rpms to gain anything from it but it doesn't hurt. I just wouldn't spend the money to have the rods micro-polished.

I'm sure others might have a better explanation but I thought I would add my .02.

Forged rods: You benefit from forged rods due to the grain structure created during the forging process. The grains all line up in a nice flow pattern that creates a stronger structure. You can still benefit from polishing and shot peening, but most don't need it unless it is a factory forged rods that usually ridge same as a cast.

Powder metal rods with cracked caps are technically the strongest rod made. BUT that is there down fall as they have no give like a forged, aluminum or titanium rod. I like to believe this is the reason why Ford went to PM rods in the 7.3. When ford started getting all these engines back for warranty claims due to broken rods they designed a stronger rod. But in hind-sight it was the Western Diesel tunes with generous portions of propane that was breaking rods.

Thats just my thought.
 
It is hard to quantify something like this but in my opinion, it does very little to increase ultimate strength. Meaning if you've bent rods at 1000 hp and you're looking for a little more power this year, they probably won't hold up. Now say you wanted to run a fun 800 hp twin setup for a few years, I'd look into it more.
 
None of these things prevent bent rods.
Bending rods is a different version of strength. If you bend a rod, that rod was incredibly strong, it didn't separate. All of the stress relievers prevent separation.
As far as i know, prevention of deformation only comes from design ques. Not stress relief.

Squeaky Wheel
 
It all does a full circle back to tune-up. Some folks can make more with less and others not so much!

I'm still amazed they way people with electronic tuners will throw box's at there trucks and hope it stays together.
 
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