Exhaust Manifold Torque Specifications for a 350by Richard Rowe
Say the words "three-fifty" to anyone remotely familiar with the automotive world, and odds are the first thing they'll think of is the original Chevrolet small block. However, this storied displacement spans three generations of Chevrolet/GM V-8: the original small block, the second-generation LT1 and the LS1 that came to replace it in 1997.
Bolt torques remained fairly consistent from the original small-block's introduction in 1955 until it was discontinued in 2002. The first-gen small block uses 3/8-inch exhaust bolts and nuts with 16-pitch threads, which should be coated with anti-seize compound before they're torqued to 25 lb.-ft.
GM introduced the second-gen LT1 in the 1992 Corvette as a modern update to the original small block. Most of the LT1's parts interchange with its predecessor's, and bolt torque specs are similar. Torque the LT1's exhaust manifold nuts and bolts to 30 lb.-ft.
Also known as the Vortec, this engine was a clean-sheet design that shared not a single component with the original small block. The LS1 is a thoroughly modern engine, easily as advanced as anything on the road today and requires a whole new set of maintenance procedures. Torque the LS1's exhaust manifold bolts in two stages. Torque all of the bolts to 11 lb.-ft. on the first pass and 18 lb.-ft. on the second pass. The exhaust manifold heat shield bolts go on at 80 inch-pounds (not foot-pounds), the pipe-to-manifold bolts go on at 26 lb.-ft. and the manifold pipe nuts spec out to 26 lb.-ft.
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