360X heads flow numbers out!!!

Unfortunately, it looks like a spring issue. The installed height on the heads using the stock valve is 1.62 which is .060 short of std at 1.68, IIRC.

Whoever designed the core boxes really dropped the ball on this. The only fixes would be to cut the spring pad, run longer valves (if available) or + style retainers and locks to gain spring height. They should have been designed to use a 1.800 or better installed height, better spring selection opening up the use of aggressive camshafts.

To me, they turned a head with really good potential into a paperweight.