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2. Does anyone know the exact specs for pressure plate bolts for the LT5 OEM Valeo pressure plate? Are they 3/8-16 x 2.125"? I'm not sure what the current carolina pp uses.
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Short answer, NO, they are not just a 3/8-16 x 2.125" bolt, regardless of the grade. They are a special bolt, designed for a specific purpose. The bolt is not designed just for axial clamping force, but also to resist shear force against the pressure plate when the clutch is engaged.
The following photos show how the OE Pressure Plate bolts engage the flywheel to provide maximum shear resistance and whereas a typical bolt does not.
Photo 01
Note the full diameter shank extends below the pressure plate and ultimately into a close tolerance counterbore in the flywheel.
Photo 02
The counterbore in the flywheel is abt 0.150" deep, which receives the 0.375" diameter x 0.088" bolt shank. The purpose is to provide maximum shear resistance, which a standard bolt will not do.
Photo 03
Correct Pressure Plate bolt installed in the flywheel to demonstrate correct fitment.
Photo 04
Demonstrates how a standard bolt cannot provide equal shear resistance, due to two, primary reasons.
(1) the root of a typical 60 deg, V thread is 22% less in diameter and 38.5% less cross sectional area than the 0.375" OE bolt
(2) A typical bolt thread will have a sharp bottom at the thread root, i.e. a stress riser, the origin point of breaks.
Photo 05
Comparison of the OE Pressure Plate Bolt to a standard bolt. The grade of the bolt, 3, 5, or 8, all have the same thread form. The critical dimensions are the shank diameter & length, both lacking in the standard bolt. Cutting the bolt off to the proper length, still leaves exposed threads above the surface of the flywheel.