The Rear Main Seal groove in early TA Aluminum 455 Blocks was cut slightly too big, requiring the use of a slightly larger rear main seal. Using any other rear main seal in early production blocks (Under S/N 035-ish) runs the risk of spinning in the block.
Modern Viton seals for your Buick engine! TA Performance has developed these Viton seals specifically for your Buick engine. ALL other (neoprene) seals on the market that are being sold for use on Buick engines are actually seals designed for other engines that just happen to fit the Buick blocks. While they do fit, they don't fit perfectly, and run the risk of leaking.
Viton is a premium seal material that has a higher heat resistance and better chemical resistance compared to Neoprene. Neoprene seals have a chance of lightly melting on first engine startup which can lead to leaks later on. The higher heat tolerance of Viton can avoid this issue. This is why we specifically chose to make our seals out of Viton and not Neoprene; to provide you the best product available!
Installation of these modern seals is much easier than the old style rope type seals, ensuring a positive seal every time. All of our rear main seals are No Trim, Direct Fit, while other suppliers offer a more difficult to use Trim-to-Fit seal. The use of Viton seals will also free horsepower because the drag on the crank is only a fraction of that compared to rope seals.