Rule of thumb is that when everything is setup perfectly, you gain 2hp per 1cfm. This is far from a perfect scenario, but we should have no problem seeing an additional 25rwhp using these ported Apache heads over our ported 6.1 heads. These heads should easily support 750hp NA.
The only loss was at .200". Increased everywhere else. This was ver 1.0 of the apache Intake/Exhaust port. We put allot of effort in the exhaust port in order to increase the exhaust to intake ratio which isnt very good in stock form.
Stock Exhaust/Intake Ratio: 61.7%
Ported Exhaust/Intake Ratio: 65%