STAINLESS STEEL Standard Hexagon Head Bolts To Fix The Inlet Manifold To Your Rover V8 Engine. HEXAGON HEAD STAINLESS STEEL. RV8-1.3.1 Rover V8 Engine Inlet Manifold Bolts. One Spare 2" Bolt Is Included For The Manifolds With An Extra Thick Boss Cast Where There Used To Be A Thinner One.