Why purchase your Edelbrock Big Block cylinder heads in a total box stock format when there are some small changes that can boost performance by as much as 50 horsepower. These heads while nicely done by Edelbrock have some weak areas that can quickly be improved upon. Using a pair of bare heads we perform a true competition valve job, chamber de-shroud, back-cut the intake and exhaust valves, fit the heads with our r-1 valve springs, and set the valve guide clearances. Once the modifications are performed the heads are then flow tested to verify the performance on our flow bench. These heads are 100% ready to bolt on and go.