I bought an '89 Integra with 170K on it -- she's blowin' more blue smoke than I counted on ('bout 1 quart of oil/300 miles). I'm 90-95% certain it needs a valve job (runs great, just pollutes way too much, esp. just after laying on the throttle after coasting).

My main question is: Assuming it's in relatively good shape, how well can I expect the bottom to hold out if I throw in a rebuilt cylinder head?

I've read that the increased compression of a rebuilt head can cause the already worn piston rings to fail. I know the original owner, and believe the car to have been driven conservatively and well maintained.

Anyone go through this?
Do I bite the bullet, and drop in a used engine?

 

Are you sure the rings aren't toast right now? I would do a compression test and see if the numbers go up when oil is added to the cylinders. If compression goes up, it's usually the rings that aren't sealing. If it stays the same, then it's usually the valve seals.