A few weeks ago there was a thread on this board that somehow got into the discussion of LT4 rocker studs. There was some question regarding the size and configuration of these studs. Well, I've "looked into it" and here's how it is:
The LT4 rocker studs are 3/8" studs with 7/16-14 base threads. This same basic size was used for all earlier small blocks with screw-in rocker studs (70-81 LT-1 and L-82). They are of a rather unique configuration, though, inasmuch as they are designed for use with the GM-style roller rockers. They have an unthreaded shank section of 1" length topped by a reduced-diameter threaded section of 5/16-28 thread size and 7/16" length. These studs are of GM #12550011.
The LT4 rocker nut is generally a typical-configuration roller rocker nut. However, although there is an unthreaded hole in the top, there is no lock screw used. Considering the relatively short thread length of the stud and the mating chamfers on both the stud and the nut, it appears that this assembly is to be used in a "net-lash" arrangement. In other words, there is no adjustment of the rocker arm as in the traditional small block Chevrolet arrangement; the rocker nut is simply torqued down to a specified torque and that's it. These nuts are of GM #10215349.
The LT1 rocker stud is similar to the rocker stud used for earlier small blocks with screw in studs. It is a 3/8" stud with 7/16-14 base threads. The primary difference is the shorter length of the base thread section. The shorter length of the base threads accomodates the fact that no "guide plates" are used with most LT1 applications (except 1992 which used non-hardened plates as an assembly aid). The 93-96 LT1 stud has an unthreaded shank 5/8" in length and a 3/8-24 threaded section 13/16" long. The base thread section is 7/16-14 X 9/16" in length, just like the LT4 stud. These studs are GM #12552126.
A picture is provided to illustrate the configuration of the LT1 and LT4 studs as well as the LT4 rocker nut:
The LT4 rocker studs are 3/8" studs with 7/16-14 base threads. This same basic size was used for all earlier small blocks with screw-in rocker studs (70-81 LT-1 and L-82). They are of a rather unique configuration, though, inasmuch as they are designed for use with the GM-style roller rockers. They have an unthreaded shank section of 1" length topped by a reduced-diameter threaded section of 5/16-28 thread size and 7/16" length. These studs are of GM #12550011.
The LT4 rocker nut is generally a typical-configuration roller rocker nut. However, although there is an unthreaded hole in the top, there is no lock screw used. Considering the relatively short thread length of the stud and the mating chamfers on both the stud and the nut, it appears that this assembly is to be used in a "net-lash" arrangement. In other words, there is no adjustment of the rocker arm as in the traditional small block Chevrolet arrangement; the rocker nut is simply torqued down to a specified torque and that's it. These nuts are of GM #10215349.
The LT1 rocker stud is similar to the rocker stud used for earlier small blocks with screw in studs. It is a 3/8" stud with 7/16-14 base threads. The primary difference is the shorter length of the base thread section. The shorter length of the base threads accomodates the fact that no "guide plates" are used with most LT1 applications (except 1992 which used non-hardened plates as an assembly aid). The 93-96 LT1 stud has an unthreaded shank 5/8" in length and a 3/8-24 threaded section 13/16" long. The base thread section is 7/16-14 X 9/16" in length, just like the LT4 stud. These studs are GM #12552126.
A picture is provided to illustrate the configuration of the LT1 and LT4 studs as well as the LT4 rocker nut:
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