2 years ago a pair of heads was brought to me from a 1992 305 in a country pickup which was smoking on startup and idle but little oil consumption.
The truck had over 200,000 on the clock--engine was fairly clean inside except for hard carbon as in baked, built up 1/4" thick in the drain back area between the two center cylinders.This prevented proper drainage and flooded some of the guides when high flow was present.
The valves were great, the guides were relatively tight and the cylinders had factory crosshatch visable within 1/2" of the top.
I reamed for OS stems, new seals, and a proper valve job and the customer was reportedly happy.
The late small blocks will run 300,000+ with reasonable care.
