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Pedestal mount rocker thought
#1
So, if the bolt for the pedestal rockers are the weak link in the valve train, why can't someone just use stainless bolts instead of the steel ones? I understand the "stretch" concept of the steel bolts but stainless is a lot less likely to "break" without a shear point or twist factor. And I know they make a certain compound for torquing stainless bolts. I know you probably shouldn't do it, but was just curious if anybody has a metallurgical reason for not doing so?
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#2
It's not as much the bolt strength as the pull-out strength of the threads in the heads. The side loads on the rocker studs is fairly low. As the valve spring rates go up the rocker pulls up on the stud more. And, it's not a steady pull, but varies from seat pressure to open pressure up to several thousand times per minute.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#3
Stainless does not mean stronger as there are many grades in both steel, SS, Titanium, Chrome Moly steel etc. ARP is your best bet for strength as its geared for automotive uses and therefore tested against heat cycling and bolt stretch so they(ARP) will choose the highest tensile strength fastener for the specific application.
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#4
InjectedMach;214004 Wrote:Stainless does not mean stronger as there are many grades in both steel, SS, Titanium, Chrome Moly steel etc. ARP is your best bet for strength as its geared for automotive uses and therefore tested against heat cycling and bolt stretch so they(ARP) will choose the highest tensile strength fastener for the specific application.

Injected is correct, many factors go into choosing a bolt. The following chart shows the yield and tensile strengths of steel bolts and one type of stainless.
While this stainless material can be had at tensile strengths equivalent to grade 8 bolts, the yield strength is not as high. Yield strength is the point that the metal is permanently deformed, and will not rebound back to its original shape.

.jpg   Bolt Grade Markings and Strength Chart.JPG (Size: 78.23 KB / Downloads: 25)



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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