The Iron Alternative

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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