What diameter pushrod do I need?
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From: Perry, GA
What diameter pushrod do I need? Planning on a cam change this summer and trying to decide what diameter pushrods and/or wall thickness pushrods I need. Engine is an L99 converted to an LS3 in a 2011 Camaro. Present pushrods are SAE 4130 ChromeMoly Steel at 5/16" dia x 0.080" wall. New cam may, if I'm lucky, add 70 FT-LB of torque and 30 RWHP. It has been suggested that I change the pushrods to either 3/8" dia x 0.080" wall or 5/16" dia x 0.105" wall.
My napkin math doesn't support needing to change pushrods, and this is based on what info I can find on the mechanical properties of the OEM pushrods vs: the SAE 4130 pushrods. Best I can find the OEM rods are made from SAE 1010 steel and have a wall thickness of 0.06x". Based on the yield strengths of the two alloys, the 4130 is twice that of the 1010, and the wall thickness is at least 30% greater. Scribbling this all down leads me to believe the 5/16" dia x 0.080" wall rods are over twice as strong as the OEM rods, or good for at least 852 Crank HP. Since I'll be nowhere near that I see no reason to change pushrods again.
What say you experts?
My napkin math doesn't support needing to change pushrods, and this is based on what info I can find on the mechanical properties of the OEM pushrods vs: the SAE 4130 pushrods. Best I can find the OEM rods are made from SAE 1010 steel and have a wall thickness of 0.06x". Based on the yield strengths of the two alloys, the 4130 is twice that of the 1010, and the wall thickness is at least 30% greater. Scribbling this all down leads me to believe the 5/16" dia x 0.080" wall rods are over twice as strong as the OEM rods, or good for at least 852 Crank HP. Since I'll be nowhere near that I see no reason to change pushrods again.
What say you experts?
How do you figure that your 5/16" .080" wall pushrods are good for 852hp?
In my opinion, if you have 5/16" .080" wall 4130 grade pushrods in a naturally aspirated LS engine making 850hp, you should make about 900hp if you upgraded to 3/8" or even 7/16" pushrods.
In my opinion, if you have 5/16" .080" wall 4130 grade pushrods in a naturally aspirated LS engine making 850hp, you should make about 900hp if you upgraded to 3/8" or even 7/16" pushrods.
Thread Starter
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From: Perry, GA
You guys don't understand the question. The LS3 from the factory makes 426 HP with OEM pushrods, therefore pushrods that are twice as strong should be theoretically string enough to handle 2 x 426 = 852 HP. My NA motor will never make anywhere near that, which is what I said in my OP. I simply want to know if my bar napkin math makes sense and if the 5/16" x 0.080" wall pushrods are strong enough for a NA LS3 build. Either my writing skills, or your reading comprehension skills, need help.
And to Tim, bigger is not always better in the mechanical and engineering world. And why would I want to spend money for pushrods, if my present pushrods are adequate?
And to Tim, bigger is not always better in the mechanical and engineering world. And why would I want to spend money for pushrods, if my present pushrods are adequate?
Last edited by jeffbrown13; May 14, 2014 at 05:03 PM.
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Thread Starter
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From: Perry, GA
No kidding, I'm sure you do too in certain disciplines. I thought the purpose of this forum was to help those of us that don't have the answers obtain them. I'm 69 years old and don't give a rat's patoot what you think KCS. If you don't want to help me obtain an answer to my question, or have anything constructive to add, then shut up. Maybe you think it's just a place for know-it-alls like you to pat each other on their backs.
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Verdad Gallardo No kidding, I'm sure you do too in certain disciplines. I thought the purpose of this forum was to help those of us that don't have the answers obtain them. I'm 69 years old and don't give a rat's patoot what you think KCS. If you don't want to help me obtain an answer to my question, or have anything constructive to add, then shut up. Maybe you think it's just a place for know-it-alls like you to pat each other on their backs.
Thread Starter
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Joined: May 2013
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From: Perry, GA
I don't mind constructive criticism, but that is not what KCS gave me. He gave me smart ***, schoolyard bully comments, and after that I really wouldn't value his opinion anymore than I would a 12 year old.