Hi can any one tell me if the 1994 4.3 engines code W and Z engines will inter change as far as long blocks go.

 

No. The heads are different on the code W. The W has threaded rocker arm studs and the Z has pressed in studs although MAY have threaded studs. This is straight from the factory service manual for a 94 S/T series truck & Blazer.

 

They may still be interchangable though. I know I would rather have the threaded studs if I could choose.