When rebuilding an engine, there are several stock parts you wont want to reuse. Stock head studs stretch over time, and even more so each time they are re-tightened. If head studs stretch, head gaskets can blow, and possibly even worse. Racing puts more strain on an engine than it was meant to handle from the factory, it is normal for stock head studs to stretch in high power applications. Head studs are a low cost item that can mean the difference between blowing a head gasket, or not. Use ARP Head studs for your engine build.