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455 Rear Main Seal

Guest Perk

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I am replacing the rear rope style rear main seal in the 455 buick motor that is in car with a new Viton seal, with motor in car & was wondering if anyone knew if the 455 Buick from 72-75 had the anti rotation holes in the block for the stock rope seals as they have to be filled with silicone if there were, There is no holes in main cap for anti rotation but I was told Pontiac had them & also some of the Buicks had them in the block, I have no way of telling without dropping crank down which I would prefer not to do if at all possible, I was also told if there are none in cap there is none in block, If anyone know for sure Please let me know ?

Thanks Perk

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A search of RockAuto for Buick, Pontiac, and Olds V-8s of that era all show a particular nitrile rear main seal for MANY years of vehicles. It looks a little suspicious that Olds 307-455 V-8s, Pontiac 455s, and Buick 455s all use the same 5095 rear seal upgrade. Be that as it may.

In general, I've never heard of a rope rear main seal "rotating" in its slot in the block/rr main cap. IF it did, considering it started out as a snug fit, it'd self-destruct itself in a short time and them oil would pour from the rear of the engine . . . which might be why some perceive there are retention slots to prevent such. The rope, itself, is impregnated with some sort of graphite substance for friction reduction after it's snuggly pressed into its slot.

Similarly, the nitrile (i.e., rubber) seal will also press into the same slot the rope seal pressed into. There should be a knurling on the inner diameter of the seal to assist in oil reversion to the crankcase. The seal will be a snug press fit such that NO oil should get past it to any retention slots in the block/crankcase, plus having a solid seal all the way to the lip portion of the seal. There, as I suspect, are NO "thru holes" for any oil to pass through between the crankshaft seal area and the metal the seal is pressed into.

Just my gut suspicions . . .



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