Well, I have a '90 chevy 1500 with 200 K on the motor. I have recently replaced the rear main seal in hopes to stop an oil leak. In doing so I have somehow created blowby or something is SERIOUSLY messed up. Is it just that the engine is shot or could my mechanic have messed soemthing up? My father says it could be deposites making the valves not seat right, but I think it is just a piece. I was wondering if anybody would know where I could find an inexpensive crate motor or a lower-miles used engine. It has to last through the year.