overtightened cylinder head studs

[tiderider]

A friend replaced valves on his pwc and installed ARP Head studs instead of the stock head bolts.
He put 30 hours on it and decided to retighten the head studs incase they loosened up.
He's a big guy, with strong forearms and while torqueing the studs at 100 lbsft he noticed that his torque wrench may have locked up and accidentally tightened down the studs more then 100lbsft, maybe 150lbsft.

Would it be a problem if he did accidentally torque down 1 of the studs tighter than required?
Can he loosen back the stud and re torque to the correct specs? Antifreeze is in the engine. Thanks

[DR2006RXP]

I would contact ARP to get measurements for the bolts they might be stretched far beyond yield .

[Cosmicbrut]

I’m not sure if torquing one down too much can warp head. What I can tell you is be careful how many times you reuse the head studs. This happened to me on third use on my ski. Broke torquing to 100 lbs.

[Slow 91]

over torqueing I have seen pulls the threads right out of the block. I had a local guy torque them to 115ft by mistake and it pulled the last one out.

[tiderider]

I'll suggest to leave it alone. He didn't break or pull the threads off it. Thank you

[mibunkerking]

over torqueing I have seen pulls the threads right out of the block. I had a local guy torque them to 115ft by mistake and it pulled the last one out.

Ditto, had this happen to me a few years back. Torqued to 100 ft lbs. 2 hours into break in there was a very loud ping while sitting on the beach cooling off. Started leaking coolant from the head gasket after that. When I pulled the stud out the threads came out with it in a perfect coil. Started torquing them to 90ft lbs after that no issues.

[tiderider]

Would it be safe or better to slightly loosen that one stud in particular and re torque? Will it damage the head gasket or seal poorly afterwards?

[nmpeter]

just check for snappage after 20 hours