i just bought a 1985 silverado pickup(future drag-car hauler) for a steal at 250.00.i hear what is possibly a connecting rod knocking but it only starts after a 5 minute warm-up.has anyone heard of a rod only knocking after the engine warms up?

Possibly...
Clearances increase and oil thins after warm up.
I had a 350 motor in my Camaro when I bought it that only rod knocked between 2200-2800 RPM. Even drag raced it quite a few times one night. Good oil presssure, too.
Upon teardown found #7 rod bearing had totally spun. :eek:

ok,thanks! graemlins/waving.gif

Maybe that's why it was so cheap. Guy figured it was on it's last leg. Tear it down before you spin a bearing.