Changing B20 front crank seal from felt to silicon

I'm not a big fan of felt seals, and arriving at a roadworthy test only to have the tester advise you the front of your engine is leaking through the felt seal at the front of the crankshaft is not a recipe for success.

Off the shelf solutions exist that have a modified front timing cover to accept a silicon seal, but when fixing up my last B20 I decided to experiment with a file and an off the shelf silicon seal from my local auto bearing shop. For the ~$15 cost it seemed worth a shot.

Unmodified cover front

Unmodified cover rear

I picked a seal that fit around the pulley sleeve (52mm), fit inside the factory timing cover hole (66mm - be sure to measure yours before attempting), in the widest available size (7mm). The seal is designed for clockwise rotation when looking at the front of the engine.

I then took a file and removed a small amount of material from the timing cover to allow oil to drain out of the seal and back into the engine. Being careful not to file into the outer surface the seal would later require to keep the life juice in.

And pressed in the seal after applying a small amount of engine oil

Hopefully this works as well as it did on the last engine I tried it on!



  • Nice work.

    Back in the mid 80s, dealers doing timing gear replacements used to machine the pre-74 timing covers to fit the 74+ neoprene seal, if the customer gave the nod. There seems to be a trend these days to replace a pre-74 cover for a later one, but as you've shown, it isn't necessary. Likewise, the rear main oil seal cover was machined to fit the neoprene seal while doing clutches in those days.

    When rebuilding B18s / B20s, it's prudent to make sure those sealing surfaces at the front and rear of the crank are round and smooth, so the neoprene seal won't leak.

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