I've been running a CSR for going on four years now on my street strip car with no issues with the o-rings although one did "fray" a bit after five or six r-n-r cycles, I bought spares. I put a little bit of vaseline on them to keep them in place when bolting the pump to the block plate. I'd make sure that the CSR block plate is clean as well as the pump surfce and try again. Be sure you have even torque on the bolts as well and that the timming cover isn't warped or has excess left over gasket material where the block plate seats to it. The miiled receiver ring for the o-rings is supposed to be shallower than the ring itself so there is adequate crush to create the seal.

Most new OEM stuff is moving to o-rings and they really do work well.

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Bill Fowler
71 Mustang Convertable '03 Harley Davidson F-150