| Re: Phase 6 bowtie heads
They were one of the progression series of bowtie racing heads. Based on the photos I've seen in Vizard's books, they appear to have the same port layout, and the same chamber shape, as 92-96 aluminum LT1 Y/F car heads, 94-96 iron LT1 Bcar heads, and 1996-1999 Vortec iron L31 truck heads.
IOW they are high flow, fast burn heads that were the racing head development that led to the LT1/L31 production car/truck heads. They are good performance heads, but the only advantage they might have over L31 Vortecs is that they might have thicker walls so they might be able to be ported better than the car/truck heads. | 
