Yeah,that threw me for a loop,too! But if you read the article carefully,and their explanation for why is hurts flow,it seems to make sense. Just goes to show that a flow bench beats common sense sometimes. And I hate to say that.

Re: reduced stems under the valve
 

One has to accept some of the new technology without much question . . The Vortec head, by itself, makes you ask, "Why didn't they think of this 30 years ago?" and the Gen IV heads . . Little skinny valve stems, literally flat valves, no seat pressures, high ratio rockers . . all 180° to where we've been going on normally aspirated Engines for 50 years . .

Basically, what we know sometimes isn't what we need to know . .

yep...flow benchs dont lie......:)

Yep the fast flow vortec's surprised me as well about the small stems flowing less, i guess it's all about volocity/air speed. I would have never thought that :oops: I've alway thought bigger is better, but i guess the Vortecs is an almost perfect head for the street motor on pump gas. I guess it's kinda like the LS1/LS3 heads they flow like a big dog and produce big HP and torque in stock form. I guess GM is not so dumb after all :lol:

Zip.

Preach it Brother Zip! [/img]

vortec
 

Read somewhere that the vortec head is the best flowing factory cast iron head out of the box. Have people made 461's flow better? Yes, with alot of work. But, unmodified, Vortec flows best of all the factory cast iron heads. As far as the valves, it's the design of the head that will not allow it to respond to the smaller diameter stem. Much like overporting any head will decrease flow, same concept sorta. Like the article kinda said if you want to go over 400 HP with less than 400 cubes, you'll exceed the ability of the Vortec. Up to 400 HP, it's the best/cheapest way to go.

I have built alot of circle track engines with 906 vortec heads 11:01 solid flat tappet cam 600 HP carb and its no problem to make over 500 horse.

People race flow benches all the time you have such a thing a quanity of flow and then you have quality of flow!!!!

I have seen where the Bowtie heads will out flow the Vortec heads but the Vortec heads make more power!!!

The Vortec heads have raised intake ports and exhaust ports and a fast burn chamber its not a bad head.

The Mexican casting are not as good as they have to small of intake runner 158 CC compared to the non mexican castins which are a true 170 CC intake runner.