Crank Case Pressure High

I had recently bought a 1986 Chevy S-10 Blazer under the assumption that all it needed was a rear main seal. Pulled the motor and replaced the seal, all was fine. Not more than 20 miles later oil is pouring out of rear seal again. I further investigated the motor and noticed smoke and alot of pressure being built up in the crank case. What might be the cause of this and would it make my new seal go bad? At a big loss and need some advise.

Possibly a bad oil pump...I've seen them go high before quitting all together before.

Thanks rlith but oil pressure is not my problem. Oil pump was replaced when I put the new seal in. Check bearings and all check out ok.

Possibly a silly question, but was the oil pump primed properly when it was installed?

Yes, I packed the oil pump with vasoline. Silly question, maybe but would the oil pump cause pressure in my ventilation? I have mad amounts of air being blown through my valve cover.

anything is possible... I'll have to ask a buddy of mine with more experience in that department...Another silly question, how is your PCV system and vac system?

I need to rebuild or replace my motor. So thanks rlith for your help in trying to diagnose my problem.