It Is For Good Reason That Virtually Every Top Professional Engine Builder Relies On Arp Pro Series Head Studs For Their All-out Competition Powerplants. Simply Stated, There's Not A Better Stud Set Up On The Market Today. For Openers, Arp Uses A Premium Grade 8740 Alloy That Is Rated Far Superior To Aircraft Quality. Then Each Stud Is Placed Vertically In Special Racks And Precisely Heat Treated To 200,000 Psi. This Procedure Ensures Complete Heat Penetration And The Results Are Far Superior To Those Lesser Quality Studs From Other Manufacturers Who Just Dump Pieces In A Basket And Hope For The Best. You Will Also Note That Arp Offers Specially Undercut Studs For Several Engines. This Procedure (done Only To The Shorter Studs) More Equalizes The Stretch Of Both Studs, Which Makes For A More Consistent Clamping Force - And One That Compensates For Head Gasket Compression When The Cylinders Are Installed. This Helps Prevent Blown Head Gaskets, And Assures Optimum Sealing! Arp Head Stud Kits Are Available With Your Choice Of Conventional Hex Nuts Or Compact 12-point Nuts. Premium Quality Ground