These heads come ready for the maximum street/strip Small Block Ford performance possible. They are not emissions legal. With the 165 coming with 1.900 intake and 1.600 exhaust valves and the 185 sporting 2.020 intake and 1.600 exhaust valves. Both heads feature 58cc or 61cc combustion chamber with 69cc exhaust ports. Both the 165cc and 185cc have available as an option nitrous or blower exhaust ports featuring either a 75cc ultra high flowing exhaust port. With AFR’s trademark 3/4” thick head deck, it’s no problem handling that additional cylinder pressure. Each head is also drilled for the larger 1/2” head bolt hole for maximum head gasket retention as a standard feature of this serious race piece in street disguise.

Note:
Hydraulic roller cams typically experience valve float at 5800-6000 rpm because of their fast ramp rates. AFR suggests you upgrade your springs to AFR part #8032, 1.530 O.D. with higher spring pressures to reduce chances of valve float associated with rpm’s 6000 or higher.
(Flow Charts at bottom of page)