516 head question

RustyRatRod said
@IQ52 May can shed some light. What say you, Jim?

Cody fiddled with the 516's a little bit on the low compression 440 tests. He is in the mountains with his wife today or I could ask him more. I believe we put stock 1.74 valves in the heads and he did some porting.

Lift..............IN/EX
.200........160/132
.300........210/182
.400........237/203
.500........250/216

The engine had a 509 cam with a MP M1 single plane, a 850 Mighty Demon and our dyno headers.

Test (1) stock 906 heads @ 7.45:1 compression. Test (2) ported 516 @ 7.9:1 compression.

RPM...........#(1)HP...............#(2)HP.........HP gain/loss
4,900..........387....................428.................+41
5,300..........377....................449.................+72

Peak to Peak gain (387 to 449) was 62 HP. So under the above circumstances ported 516 heads made a significant difference.