Quote:
Originally Posted by DrBacon
When they pull your engine apart out of curiosity ask them if the head studs were loose. I've seen it happen with plenty of arp lube and torqued to 95lbs after a couple hundred miles they loosen up, no one has been able to really give me a straight up answer as to why that happens. ARP claims you don't need to retorque them after the first heat cycle, and honestly very few people probably do considering the amount of work required to do so.
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Having to retorque head studs is nothing new, its just that its a big dilemma for VQs and similar engines that practically need a rebuild to get in and retorque them. Its why lots of experts strongly prefer torque to yield fasteners. Im sure its a result of the heat cycles and thermal expansion. You torque it, and it has X amount of load on it. Then it all gets hot and it wants to expand more than the stud allows it to, now increasing the compression/load on the threads. This is likely causes permanent compression to the head gasket and pulls the threads in the block a little and digs the washer into the cylinder head a little bit, etc etc. Then things cool back down, and contract a little bit... but the space that was made remains, and youve lost compressive load until you tighten the stud further to make up for the space that was made.