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, thereâs not a better stud setup on the market today. For openers, ARP uses a premium grade 8740 alloy that is rated far superior to âaircraftâ quality. 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. Following heat-treat, each stud is centerless ground to make it as close to perfectly concentric as possible. This procedure involves about ten very slight cuts and results in an exceptionally straight part. Itâs important to note that lesser quality studs are not even centerless ground â the material is thread rolled in bar stock form (mostly before heat-treat, when the material is easier to machine). Because ARP studs are manufactured to such exacting tolerances, you will note that gaskets and cylinder heads literally glide into position and are perfectly aligned â something that wonât happen with inferior quality head studs. ARP studs are thread rolled after heat-treat, which gives them about 1000% (thatâs ten times) better fatigue strength than those studs that are threaded prior to heat-treat (a very common industry practice). It costs a lot more to do it this way, because itâs tough on tooling, but the results are well worth the extra effort.
You will also note that ARP offers specially undercut studs for several engines. This procedure (done only to the shorter studs) more equalizes the âstretchâ of both studs, which makes for a more consistent clamping force â and one that compensates for head gasket compression when the cylinder heads are installed. This helps prevent blown head gaskets, and assures optimum engine sealing!
Premium quality heat-treated 8740 chrome moly steel head stud kits are available for most every domestic and import applications.
You wonât find a better quality stud on the market from any other source. Look for ARP stamped on each stud as your assurance of quality.
Clearly, ARP Head Stud/Bolt Kits are the best on the market today, and the favorite of leading professional engine builders in all forms of racing. HIGH PERFORMANCE SERIES High Performance head bolts are available with a reduced wrenching hex or 12-point and wide area flanged head that eliminates the need for valve train removal to facilitate cylinder head retorquing. All High Performance Series bolts are 180,000 psi (which is 15% stronger than Grade 8) and kits come complete with hardened parallel-ground washers. PRO SERIES All Pro Series bolts are cold-forged to ensure molecular integrity, heat-treated prior to thread rolling and machining, and are rated nominally at 200,000 psi. ARP Pro Series head bolt kits are application specific â designed for use with typically competition only components. These fasteners deliver superior strength and meet the ARP âZERO defect â ZERO failureâ quality standard. Hardened and parallel-ground washers are included with each kit to ensure even load distribution and accurate torque readings. All Pro Series head bolts have a reduced wrenching hex or 12-point head and wide area flange to eliminate the need for valve train removal for cylinder head retorquing and permits the use of larger diameter valve springs. Most applications have undercut short bolts that can help eliminate head gasket failures through providing more âstretchâ to compensate for the additional compression of gaskets. Head Studs vs Bolts. On many street-driven vehicles, where master cylinders and other items protrude into the engine compartment, itâs probably necessary to use head bolts so that the cylinder heads can be removed with the engine in the car.
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