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Discussion Starter #1 (Edited)
I know this has probably been answered a 1000 time before but what's the limit as far as horsepower figures when it comes to ls rods if they were shotpeened and had arp bolts. My cousin's n/a ls/vtec powered crx runs 12's and sees rpms in and around the 10,000 mark so i figured they'd be ok...but I'm not sure if it'd be different with boost, I plan on seeing numbers in an around 250-300 hp
 

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they can handle up to 300+ sometimes but i don't recommend going threw the hassle getting tuner toy rods are a better investment.
 

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Discussion Starter #6
yea...I was thinking about going with tuner toys but I already have the arp bolts and I got the rods with a bunch of shit that I bought, could probably get them shotpeened and deburred for $30-40...though maybe I could save bout $200 but i don't want my engine to grenade to shit...
 

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Hmm. I wouldnt worry rod bolts so much but if you have them, use them.

Lets talk about the stresses rods are put under first. Compression, and tension

Compression occurs as the piston is being pushed into the rod. During this stress the weakest part of the rod is under the wrist, failure usualy occurs about an inch from the wrist pin. Usualy comrpession failure shows up as a bend in the rod. The more HP you have the more force pushing on the piston the the more stress it is under. If the piston hits the head or a valve this also puts a great deal of compression stress on the rod which can lead to a bent rod.

Tension occurs as the piston is traveling up and the reaches it upper most travel, as the crank starts to swing down the rod tugs down on the piston but the piston still want to travel up. This pulls on the rod creating a tensional stress (again the weak part is under the wrist pin, but tension usualy snaps the rod in 2). This is also when the rod bolts come into play as while the rod gets pulled on the rod bolts are put under tension also, during compression the rods bolts dont really see any stress at all as the rod obsorbs all the force. Now on the compression stroke. compression is pushing against the piston so the rod actually sees compression force, and the compression helps to push the piston in the oposite direction as the cranks starts to swing down. This takes the load off the rod. However on the exhaust stroke there is little compression, and this is when the rod and bolts earn thier keep.

There is also of course the forces the rod must face while the rod is leaned at an angle. During this time the rod can actualy see both forces. i wont get into detail here but just picture this. if you bend a object into a U the short turn radius or the inside of the u will be under compression (compressed together while the long turn radius or the outside of the u will be under tension, or be trying to be pulled apart.


So if HP doesnt break rod bolts, why do higher hp car break rod bolts? Well this usually happens in high HP N/A cars operating at high RPM. The faster you spin the engine and the shorter the RS, the faster the mean piston speed is,which means guess what? More tension being place on the rod as it has to yank that piston down when its trying to escape through the head.


Infact, rod bolts didnt become popular is LS motors till the LS/VTEC became popular and people were trying to spin the motors 9k rpm's. Thats when rod bolts started failing. Before that I have seen too many 300-320 hp ls motors never have a single issue even without the ARP bolts. But that was because they were only spinning them to 7-7.5K.

So anyway, to answer your question. 320hp is a very safe number for ls rods. The rod bolts will give you alittle safety to get a few more revs from the motor but wont increase the compression strength (or HP level)of the rod. BTW there is many guys claiming 400+hp on ls and b20 rods with one guy claiming over 500. But how long they'll last with the much power is another story. Also keep in mind new rods will never have been put under stress, and therefore can possibly put up with alittle more abuse.
 

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uhh yeah the rod bolts might suck. but they can still handle 300 damn what are you my enemy know lol.
lol, no man. im not your enemy. I hate it when people bring up " whats a B-series doing on a D-series forum"

Anyways Ls Rods arnt good after 9300 RPM's, all together. their have been cases there they have streached and caused lots of damage. the rod bolts streighten them quite abit. but I can see that sence you are going to turbo, Ls rods will be fine. they will need a bit of modification. Which (correct me if I am wrong) may weeken the rod. But its a cheep route, and sence you are going to put the rods in the block. a little security isnt a bad option.
 

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the artist formerly known as drexelstudent11
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lol, no man. im not your enemy. I hate it when people bring up " whats a B-series doing on a D-series forum"

Anyways Ls Rods arnt good after 9300 RPM's, all together. their have been cases there they have streached and caused lots of damage. the rod bolts streighten them quite abit. but I can see that sence you are going to turbo, Ls rods will be fine. they will need a bit of modification. Which (correct me if I am wrong) may weeken the rod. But its a cheep route, and sence you are going to put the rods in the block. a little security isnt a bad option.
the modification is just machining down the width of the big end...

something like ~.020".

its really not that much material removed.
 

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Discussion Starter #12 (Edited)
hey projekzero do you think shotpeening helps and is worth it? I know it doesn't increase the actual strength of the rod but will it help in preventing the cracking/breaking of the rod along the stressed areas?
 

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hey projekzero do you think shotpeening helps and is worth it? I know it doesn't increase the actual strength of the rod but will it help in preventing the cracking/breaking of the rod along the stressed areas?
Your on top of it. It doesnt increase the strength of the material. heat treatInG would do that however the rods are already heat treat. It will remove surface imperfections that could turn into stress risers. of course the the least amoutn of stress risers the less prone to failure the rod will be, even though its no stronger that it was to begin with.

If you have the money and an extra LS rod to spare. Send one to be cut and analysed. They can tell you all the forms of treating the rod has and what other forms might help.
 
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