Fun on the Flow Bench Besides dyno testing the new Vortec Bow-Tie heads on a ZZ4 crate engine, McLaren performance also put them on a flow bench. Not surprisingly, the high-velocity, high-volume design of the heads produced very good numbers. The heads used in the test were early production examples, not prototypes. So, results should be similar with off-the-shelf parts. Here's how the numbers looked on the intake side: SMALL-PORT HEAD Lift CFM 0.100 67 0.200 136 0.300 182 0.400 223 0.500 251 0.600 240 0.700 240 LARGE-PORT HEAD Lift CFM 0.100 63 0.200 134 0.300 181 0.400 227 0.500 258 0.600 255 0.700 261 The heads are comparable until about 0.400-lift, where the runner size of the large-port head really starts to pull its weight. For comparison, we've seen flow numbers on the Edelbrock Performer RPM aluminum heads that show a intake maximum flow of around 228-230 cfm. The Performer RPM had 64cc chambers, 170cc intake runners and 2.02/1.60 valves. In our opinion, the iron Vortec Bow-Ties performed extremely well on the flow bench. In our opinion, the iron Vortec Bow-Ties performed extremely well on the flow bench. SOURCES GM Performance Parts www.gmperformanceparts.com McLaren Performance « | 1 | 2 | View Full Article Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!