These bare castings belonged to Norris Motorsports. They were at CNC Heads so Pete could work his magic. We were fortunate enough to see them in stock form for this comparison.
One of the more obvious differences in the LS6 head is the combustion chamber. A stock LS1 head (right) has a 67cc combustion chamber, compared to the 63cc chamber in the LS6 heads (left). This provides an increase in compression from 10.1:1 to 10.5:1, thus improving thermal efficiency. s
Intake port differences between the two heads are quickly noticed on the right side of the port about 2 inches inside. The ports were refined and more precisely cast to increase the engines volumetric efficiency while still retaining the proper airflow characteristics to make serious power with these heads. You can feel this difference with your fingers more than you can by looking at it.
The changes are more obvious on the exhaust side of the head. The floor of the port has been moved up .125 for better flow. Pete informs us that this is the same port-floor height as what is used in SB2.2 Winston Cup Racing heads.
As stated before, the LS6 heads are good, but that doesnt stop Pete from trying to get more power from them. Sometimes he finds out how far he can go by going too far, as evidenced by this research head. While this type of learning is expensive, the information gleaned from it can be very valuable.
With the added material in the compression chamber, Pete has more flexibility to work. Surfacing the head will keep the compression from dropping. You can also see the valve seats that were removed to allow larger valves.
Pete uses REV (Racing Engine Valves) in all of the heads that CNC Heads modifies. He has intake valves available in 2.02-, 2.05-, and 2.080-inch sizes, and exhaust valves in 1.57- and 1.60-inch sizes.
Along with the larger valves, bronze valve guides are installed.
CNC Heads uses the latest in Computerized Numerical Control (CNC) to ensure consistency and prevent weak or porous port walls.
The process is totally computerized once the head is installed in the machine.
Every head done at CNC Heads will have this CNC stamped into it. This is your assurance of the quality theyre known for.
We asked Pete the obvious question, Could we take a set of LS6 heads and put them on an LS1? He said they would bolt on, but when you look at them as a piece of the entire package, they arent necessarily the best choice. To use these heads on an LS1, you would also need to purchase an LS6 intake (to match the intake ports) and throttle body, which could easily run $1,800 plus the cost of the LS6 heads and any machine work to be done. You could get more punch for less money by modifying the original LS1 heads. The cost goes up if you have a 97 or a 98, because their valve covers use perimeter bolts instead of center bolts, and the coil mounts are different. But, if youre a proud Z06 owner, you have everything you need.