NOTE : GM uses 2 different valve seal styles on the LS motors: "Small" and "Top Hat". "Top Hat" style valve seals can only be used with single valve springs (this listing). If you are upgrading your valve springs to dual springs (Performance) and already have the "Top Hat" design, you will need to use small (Metal Clad) valve seals instead, you can get those seals from us here . . . Click Here! Viton and other seals have several very crucial differences that make them especially well suited to certain applications. While both Viton and other seals both serve as great sealing options at moderate temperatures, Viton is far superior to other seals for high temperature applications. Viton seals provide an indefinite seal for temperatures up to 400°F, and for temperatures up to 600°F they offe.
