A friend is getting ready to buy some CNC heads from CNC down in Florida, and was wondering if anyone had any flow numbers?
I found an old article that had them at 270 in at 500 lift, and 196 ex at 500 lift?
Sound pretty good/right?

 

I have the CNC Cylinder Heads, Inc. (Pinellas Park, FL) LT4 heads. The intake side is excellent, particularly when you flow it with their ported LT4 intake. However, the exhaust side was a complete disaster.... hogged out way too much and flowed under 200cfm "as received", and stalled at close to 0.500". And when both I and my shop tried to talk to Pete at CNC about the problem, he totally refused to reply, either on a phone call, or by e-mail.

 

I see, so what are you going to do with them? I have never heard stalling out at 500 lift, what did they do, go down in CFM or just stay the same on the exhaust

 

The increase from 0.500->0.700 was minimal, compared to flow charts from similar LT4 and AFR heads, same machine, same operator.

They were "fixed" to some extent, but I've never really been happy with them.

 

Thanks, I was thinking of getting the largest AFR heads for my own motor, a 396, but not till later. But the CNC's haev a great reputation, and this is the first I have ever heard of an unhappy cutomer.

 

The shop that flowed my heads had an extensive catalog of flow tests on virtually any LTx series head they could get their hands on. The CNC's were near the top on the intake, but near the bottom on the exhaust. At the time, a friend was running LPE CNC LT4's at about the 950HP level on a 383 with a Vortech. They compared his heads to mine, and even after they tweeked his LPE's, they couldn't get them to flow as well WITH THE INTAKE as the CNC's. That was Pete Incaudo's selling point - WITH the intake, they will flow better than anything out there. But on the exhaust side, the CNC's flowed 19cfm less at 0.600 than the LPE's "out of the box", and 31cfm less than the LPE's after Second Street got done with them. About 2 years later, someone wanted a "clone" of the 950HP setup, and they ordered a brand new set of LPE's, and they were even better than the earlier sets they had seen. LPE seemed to have continued to improve their ports.

I think what disappointed me most about CNC was the fact that Pete was willing to spend endless hours before the sale telling me how great his heads were, why they were the best, who he ported heads for, the work he did on the original development of the LT4 heads for GM, and then when I had a problem after the sale, he stonewalled me.

There are people getting excellent results out of LTx heads... try the guys that get the rave reviews here.... AI, Lloyd Elliot, etc. I'm thinking of upgrading the heads, going to a much bigger cam, etc., and those guys (and Bret Bauer and Joe Overton) are the people I would talk to.

 

Thanks, so basically you have to work on a good cam to compensate on the exhaust side of these heads. LPE is good, and I guess thats why allot of people have a rough time beating them.

 

I've got some flow numbers from some stock cast LT1 heads that were done by CNC Heads and then "Tweaked" by Nick Norris if you want to see them. I don't have access to my files right now but I can post them later if you want to see them. His car was a 1996Z with a forced inducted 355 that made 574RWHP with 10 PSI non intercooled and alcohol injection.

 

Recipe for exellent CNC head:

1. Intake port by CNC Cylinder Heads
2. Exhaust port by LPE