Can an engine run without the PCV valve?  I am assuming it can, but I am not positive.  Can it run with a breather cap in each valve cover instead?
Thanks,
Donny  

An engine can run without a PCV. A PCV is an early form of smog-device. Instead of venting blow-by into the atmosphere the PCV sucks it back into the intake acting like an afterburner, I guess one could say.

I'm sure there's more to it, but that's my take on the subject.

V8 Chevys used to have a breather on the oil fill tube on the intake manifold. In fact just about every old engine 6 or 8 that I can think of had a breather cap on the valve cover where the oil fill was.

What engine are you running?

— John  

When I bought the 65 Chevy C10, the man told me it was a 350.  But I am not sure.  I found numbers "mk07800" on the block in front of the right head.  And can not find any info for these block stamp numbers.  I did however put a breather in place of the PCV valve and the engine is running just fine.  Thanks for the info.  

look on the block just above where the tranny bolts on their should be a number on the block about 10 digits long that number will tell you what year and model  

A 65 C10 would probably have a 283 because the 350 and 307 V8 came out in 1968 Take a look at:
http://www.mortec.com/castnum.htm
http://www.mortec.com/location.htm

Cadman