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Originally Posted by vvv90
Then please post. I'm sure we're all familiar with his "Hello Hemi" Popular Hot Rodding article. He's one of the world's most renowned flow researcher but I've yet to see his opinion on this heads and flow capabilities and I would like to.
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Sure: directly from his article, Vizard's opinion on the flow capabilities
Flow Capability
We can see that Chrysler's engineers were targeting the best two-valve head possible. There are two important questions that need to be asked here: How well did they succeed for the head in stock form and, since no aftermarket heads are available, what is its porting potential? The graph, Fig 3, gives the answers here and you are going to like them. First, the intake port. The stock port with its 2-inch valve flowed a whopping 270 cfm at only .600-inch lift. It hit the peak flow figures, which are produced at .700-inch lift on a stock LS6, at only about 375 thousandths lift. This is good news but there is a lot more. Peak figures are not the whole story. Good mid-range figures are also important. The new Hemi did extremely well here. At 250 thousandths lift, the stock head was nearer a $10,000 Winston (Nextel) Cup head than it was to even a good modified parallel-valve head.
A check on the intake port velocity (Fig 4) showed the intake to be a super high-speed port with valve-to-port areas very similar to what is seen in Formula One. Velocity probing showed 90 percent of the port flows at a velocity greater than 90 percent of maximum. This is far better than a typical 23-degree performance head for a small-block Chevy or, for that matter, the LS6.
The exhaust port showed the same high-function trend by hitting 161 cfm at 600 thousandths lift through its 1.55-inch valve. It also had a far better than average port velocity and velocity distribution (Fig 5).
We spent a day and a half on the flow bench in an effort to find out what this head does or does not like in the way of port mods. We are sure there is much still to come, especially with some bigger valves, but we did find what it took to produce, at 600 thousandths lift, some 302 cfm on the intake and 195 cfm on the exhaust. As the nearby photos show the work to achieve this proved simple. In essence, the porting involves little more than just tidying up what Chrysler's engineers provided in the first place (great job guys).
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I think you're taking this a little too far. He only posted flow numbers which I personally can see supporting (maybe with even more port work) and boring and stroking these heads supporting 600HP. That was the point of my post. Nothing more.
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Maybe, I used to own a high performance shop, and this caused me to analyse all claims with a critical frame of mind - maybe your right; I guess I am just a bit jaded. I'm sure many other's like me came to conclusion's about the Hemi heads supporting high HP, based on Vizard's published work way, way before Fastman's "you heard it here first" headline
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I don't know how you can tell, from what I know the anti-reversion lip is on the top of the valve. But I'm sure it would be necessary if running big headers and an extreme cam to maintain low end torque, however it would sacrifice the flow if you're shooting for high end "brag-able" HP like Fastman is...Anyway, off topic. It seems like Fastman is definitely serious. Don't get me wrong, 600HP on a small block is ridiculous for a daily driver.
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Several types of anti-reversion valve are available. Here is more information on the type with a visible Anti reversion lip on the combustion chamber side, in the Fastman's picture.
See this link: scroll down to page 12 and see the sidebar “rimflow valves”
http://www.aptfast.com/Pdf/CatAPT2002all.pdf
I used them in one of my own engines.
vvv90 it was Fastman's bragging that caused me to react, I am not getting at you - I generally like your informative posts and comment.
Zilla
