Stock Pushrods with PAC 1218 springs?
#1
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Stock Pushrods with PAC 1218 springs?
i figured id ask...didnt find anything in my search specific to the PAC 1218's
can i use the stock 4.8 pushrods? FYI, im also using a stock 99 LS1 cam
thanks
can i use the stock 4.8 pushrods? FYI, im also using a stock 99 LS1 cam
thanks
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#10
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Chromemoly steel has an excellent strength to weight ratio and is considerably stronger and harder than standard steel. To claim they flex the same is simply incorrect. I suggest you do a bit more research.
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also note that all GM LS6 springs are not yelllow, and some have no marking on them at all - ask me how I know....
#12
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I don't need to do more research as I do this type of thing for a living. Here is a post that may explain more and provide more details: Link
#13
This is the only issue I have with your theory.
http://www.matweb.com/search/MaterialGroupSearch.aspx
Based on a quick search of the material properties on that site just a high carbon steel can vary from 2000 - 34100 ksi. (1 KSI = 1,000 PSI) In material selection the elasticity is many times what dictates alloy/ material. You are right that most commonly used pushrod materials have similar characteristics and that the O.D. is the single most important factor, however, I disagree with the notion that all steels are pretty much the same.
http://www.matweb.com/search/MaterialGroupSearch.aspx
Based on a quick search of the material properties on that site just a high carbon steel can vary from 2000 - 34100 ksi. (1 KSI = 1,000 PSI) In material selection the elasticity is many times what dictates alloy/ material. You are right that most commonly used pushrod materials have similar characteristics and that the O.D. is the single most important factor, however, I disagree with the notion that all steels are pretty much the same.
#14
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I see what you are saying vettenuts but like bayboy said even though most steels have generally the same modulus the hardened pushrods are still an upgrade over stock pushrods. I'm not exactly sure of the exact id and od of one versus the other but I would think the hardened ones are made to reduce flex through better manufacturing process.
#15
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This is the only issue I have with your theory.
Based on a quick search of the material properties on that site just a high carbon steel can vary from 2000 - 34100 ksi. (1 KSI = 1,000 PSI) In material selection the elasticity is many times what dictates alloy/ material. You are right that most commonly used pushrod materials have similar characteristics and that the O.D. is the single most important factor, however, I disagree with the notion that all steels are pretty much the same.
Based on a quick search of the material properties on that site just a high carbon steel can vary from 2000 - 34100 ksi. (1 KSI = 1,000 PSI) In material selection the elasticity is many times what dictates alloy/ material. You are right that most commonly used pushrod materials have similar characteristics and that the O.D. is the single most important factor, however, I disagree with the notion that all steels are pretty much the same.
Your referenice is to the material strength, which for all steels will have a large range of values depending on alloy and working (annealed, cold worked, etc). However, for all steels the modulus is 28.5e6 (or a value close to that) which denotes the stiffness. For a pushrod, the stiffness between two pushrods may be identical however the amount of load they can take prior to permanently bending will different and based upon the strength (or yield) value.
My point is that there is little stiffness gained using hardened pushrods over stock other than the stock pushrods are metric (and very slightly smaller OD). The real gain in stiffness is when the OD is increased.
#16
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I see what you are saying vettenuts but like bayboy said even though most steels have generally the same modulus the hardened pushrods are still an upgrade over stock pushrods. I'm not exactly sure of the exact id and od of one versus the other but I would think the hardened ones are made to reduce flex through better manufacturing process.
#17
Note that I did not state the strength is the same, but for two steels of different strengths that are not loaded to the point where they permanently deform the stiffness is identical.
Your referenice is to the material strength, which for all steels will have a large range of values depending on alloy and working (annealed, cold worked, etc). However, for all steels the modulus is 28.5e6 (or a value close to that) which denotes the stiffness. For a pushrod, the stiffness between two pushrods may be identical however the amount of load they can take prior to permanently bending will different and based upon the strength (or yield) value.
My point is that there is little stiffness gained using hardened pushrods over stock other than the stock pushrods are metric (and very slightly smaller OD). The real gain in stiffness is when the OD is increased.
Your referenice is to the material strength, which for all steels will have a large range of values depending on alloy and working (annealed, cold worked, etc). However, for all steels the modulus is 28.5e6 (or a value close to that) which denotes the stiffness. For a pushrod, the stiffness between two pushrods may be identical however the amount of load they can take prior to permanently bending will different and based upon the strength (or yield) value.
My point is that there is little stiffness gained using hardened pushrods over stock other than the stock pushrods are metric (and very slightly smaller OD). The real gain in stiffness is when the OD is increased.
#18
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In the analysis done, ends were free-free not constrained.
#19
The alloys will not affect the frequency at all (assuming the modulus doesn't change), unless you start to look at failure. If the elastic modulus is the same and the dimensions are the same, the stiffness/frequency are the same. There are no structural failure criteria used to establish the stiffness or elastic frequency.
In the analysis done, ends were free-free not constrained.
In the analysis done, ends were free-free not constrained.
I am not sure what program you're using for analysis, but I would've probably modeled the lifter and roller rocker as well. That way you can apply the load on the pushrod between a fixed lifter and the spring. (The roller rocker would be fixed through the bearing location.)
Kind of off topic, but modeling software only goes so far. At some point the anecdotal information engineers like to ignore becomes equally valuable. Tolerances can be too tight. Valve lash can give better performance. Stock pushrods are more likely to deflect with steep cam rates. We can mathematically prove whatever we want, but I think most of us in these forums prefer to do it on the pavement.
#20
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OK, whatever. Not going to argue but the things you mention are in the noise. In this case, the material parameter is just a constant. Run a closed form solution and show me where I am wrong. The lifter and rocker play no role in the bending stiffness of the pushrod. They play a role in the overall system and are controlled by different parameters. The discussion here is the pushrod itself and there are only four variables that apply,two of which are constant and one that plays a minor role. Run the numbers for yourself and you will come to the same conclusion.