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| 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. |
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