The opener in this post is hilariously contradicting.
love ya Rob, but not all 360 ports are created equal, not all came with 2.02, not all had good exhaust ports, not all are even the same size. 974 have probably the best workable exhaust port, 915 have a higher ssr floor, larger volume exhaust ports.. there are things they did, in casting, that made some heads even weigh more with all the extra they added for smog and just sloppiness when switching core boxes.
10cc variance int ports. Some flowed right under 200, others flow right over and into the 210 range...while 2.02 x or j might do 218-225 +/- 3cfm. Are these huge differences? Kinda and not kinda on paper.
400.00 for done ready to run heads that are know for being in the 200+ cfm range and the goal is 400? You're there. Buy'em. Worst you could do is have someone do a little porting and gain 30-50 over that. There is some room to grow with them, but the room ends near 475hp , 500 hp if you're pretty good with a grinder.
Oh, a small detail... the j heads with the lower head bolt cast reinforcing ledges shaped like rectangles, hedmans and the like 'average street headers' all rest against it and sometimes ,more than not, cause a leak. The x heads most of those headers were designed around did not have those, they were smaller.
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