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Head Studs Vs Head Bolts


NullZwei
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Is there any benefit to using head studs as opposed to conventional head bolts, such as better clamping force, etc,. on a normally aspirated engine?  What about on a turbo charged engine which I'm presently considering?  I've got to pull my head so this would be an opportune time to switch to studs if there is any benefit to be realized from using them.  Also, what are the pros/cons re: reusing old head bolts?  Is it beneficial or necessary for that matter to replace rather than reuse old head bolts?   Thanks in advance for your considered opinions.

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Up to 250 hp NA the stock head bolts are just fine (that is as much as I have ever made with a NA M10 with stock head bolts, don't know where the failure point really is). I have not seen any reason to use the ARP studs other than the BLING factor ( and I have used a few sets in my life) Almost everyone that has used the studs has a problem with oil leaks at the rear 2 studs that are outside of the valve cover. The one major drawback to using the studs is serviceability in the car. With head bolts you can remove the bolts and remove the head with the intake and exhaust header still bolted to the head, with the studs you can't lift the head off the studs with the header still attached, and the distributor still on the head. Find some place else to spend your $200.

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I replaced the stock bolts when I did a top end refresh on my tii a few years ago.  They were relatively inexpensive (sourced from Autohaus AZ?) since I did not know about the history of the existing ones.  IMO one of the most important things is to clean out the head bolt recesses before you install any bolts/studs. 

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By clamping force you mean modulus of elasticity. A modern stud can be extremely strong and can have less elongation than an OEM bolt. However, unless you are going to significantly increase your peak cylinder pressures to the point where the head bolts stretch enough to let combustion gasses leak there is zero need to upgrade. I would suggest this. Look at the 2002 turbo head bolt PN. You know that will be good to at least 177 lb-ft (since it is not a torque to yield bolt it will hold more than 177 ft-lb safely). If you plan to go higher consider upgrading if you don't stick with what works.

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