What is the difference between the hi-po #690 and #583 head castings?
The 583 head is thicker under the spring pocket. It’s setup for higher spring height and pressure. The Z-11 cam had more lift and stronger springs. According to the Service Bulletins, the 583 heads entered production on Nov 18th, 1963 (into ’64 production). They have nothing to do with the Z-11, but were needed because of the new 7735 cam (also known as the Z-11 cam, but this cam was in all 400hp and 425hp engines after 11/18/63). The cam had higher lift, requiring a taller installed valve spring height to avoid coil bind. In order to do this, the spring seats in the heads had to be machined into the casting. The 583 heads were cast with more iron in that area to allow for the machining. The valve head shrouding and valve diameters are the same and the heads are interchangable on any hi-perf engine (except the Z-11) as long as the ’63 cam is used. Back to the top Q: Are w-motor heads interchangable from side to side? A: Yes, they are the same and can be used on either side. Back to the
