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Old August 6th, 2018, 07:49
CJR CJR is offline
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Join Date: May 2005
Location: PA
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Re: Cylinder head bolts

For what it's worth regarding "Torque-to-Yield" (TTY) head bolts. I did a little more researching on TTY head bolts and found some interesting info. Since the head is the hottest component of the engine, local hot spots in the head that are near a head bolt can reduce that bolt's Young's Modulus of Elasticity (E) significantly and cause that head bolt to yield during normal operation. So after evaluating the equations I found, with moderate temperature increases, the reduction of (E) is significant enough for me, i.e. 20% reduction in (E).

So if your particular head has a "hot spot" that is not being cooled properly near a head bolt, that head bolt can yield more due to it's higher temperature. A yielded head bolt can reduce the clamping force on the head/head gasket and cause head gasket leaks. So in my case, I intend to change-out all my TTY bolts with ARP head bolts.

Best regards,

CJR
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