I have never bought that all the vendors we see make the heads they sell. In fact I think they really are buying CNC heads GM or others makes and then add big price tags to sell them as if they made them.

GM makes two CNC heads for performance, the more aggressive 11.2:1 compression head (PN: 88958622), or the just released 10.5:1 compression heads (PN: 88958665).

The 8622 heads have a small 62-cc combustion chamber, while the 8665 heads have a close to the production 65-cc chamber. Both heads have 250-cc intake ports, 85-cc exhaust ports, and can support north of 500 HP !
They come with the LS6 factory valvetrain, hollow-stem stainless-steel valves (sodium and potassium filled on the exhaust side), chromimum-silicon (Cr-Si) ovate beehive valve springs.

So before blowing your money on some vendor selling who knows what I cannot see them beating the design of GM engineering for high performance heads.

I was actually very surprised to mean that most o the major tuner shops do not make port their own heads at first. Then when I found out how much a CNC machine costs, the mystery was solved.

There are a few companies like TEA that do port and polish their own heads. I have found shops that actual do their own work have a quicker turn around time, because the heads are not ship 3 or 4 times.

The other thing that is pretty funny is that most of the tuners use/sell the same 'custom' grind cams from Comp Cams. One calls it "Thunder Stick O' Power" and another calls it "Screaming Demon IV"

If I do these heads and a Z06 cam, do I need to have the intake (plenum) modified? The tune would be a done deal (think I just might know someone up for the job!).

Thanks in advance,