Trick flow 175cc DHC small block chevy fast cast aluminum cylinder heads. These look like chevy Z/28 186 double hump heads with accessory holes, late 1960s but much better and are a good pick for a 327 to 350 Cubic Inch operating below 6000 RPM. A356 aluminum/60cc chambers/straight plug/23 degree/min bore diameter 4.000″ (Flowbench data @.500″ lift Int 258 cfm exh 198 cfm w/pipe.) 11/32 stem diameter stainless steel Int/exh Valve 2.020″/ 1.600″ Intake 175cc Exhaust 74cc both standard location CNC chambers 60cc Spring 1.460″OD Hydraulic roller Valve Spring,130 lbs on seat, .600″lift, Max RPM 6000 7° Chrome Moly Retainers 7° Lock Valve Keepers Positive stop Valve Seals Guide plates 5/16″ Rocker stud 3/8-16. Special order 5-7 business days. Please e-mail with questions.