Long valves on W2's with .600 lift?

Krooser said
Well I got to the shop today to pickup my W2 head. Here's the flow #'s.

dateposted-public

The intake stalled at 294 cfm...the exhaust at 230 cfm. All things considered I OK with those numbers. Porters I have spoken with say they need to square off the ports and really dig to get 310-320 cfm out of these heads. Then I recently read a tech article that discussed taking iron square port BBC heads and getting better flow when they OVAL the ports. Oh boy...

When discussing flow and lift a few years ago with Mike Jones @ Jones Cams he suggested a cam with a .565 lift as I recall. This morning Mike S., who flowed my head, told me to stay at .600 or less. Said .565-.570 is what he'd recommend. After so many years of just using a cam based on experience and a recommendation or two I can see where I used a bunch of them that were way too big for the heads I ran.

I recall using a .600 lift/[email protected] cam in my 351C 2V heads. I know for sure those were 50 CFM shy of these W-2's.

What's odd, or maybe not odd, I know guys running Brodix spec heads that flow less than what I have and they are running lifts in the .650 to .700 range. 650 HP-ish. Maybe that's why they aren't fast enough to break away from the pack... don't know.

Making the ports square is a nasty job. BTDT. The results are certainly worth the effort if you need the cross section area.

I'd disagree with the lift that low. I'm not nearly as concerned with the flow stall or even break over. I'm betting if you put the intake manifold on and flow it, the flow will be lower, but much less turbulent.

Also, the argument can be made that flowing the port at higher valve lifts at 28 inches (or higher) may not be as telling as one may think. I'm all for running the test pressure as high as you can, and doing what you can to increase flow at those pressures, or atleast reduce the turbulence/noise, but...I'm not so sure that the port sees that pressure drop at higher valve lifts.

Maybe the port only sees 22 inches above .400 lift (pulling numbers out of my hat here but you get the point) and at that pressure drop, maybe the port isn't nearLy as bad as it looks at 28 inches. We do know that at overlap and the low lift at that point that you can get a pressure drop of near 100 inches or maybe even more. One reason why I think a 50 degree seat (or even steeper) may look bad at 28 inches, but when you crank the test pressure up it looks much better than flatter seat angles.

One last thing...when you flow average verses lift, you'll see that higher net lifts gain you more time at higher flow rates.

This was a HUGE issue I had with Brookshire. He was dead set on .640 gross lift on my W2 stuff. I made more power when I changed cams and on that stuff I ended up at just under .700 lift net. With the same heads. So I wouldn't base my lift requirements just on flow at 28 inches alone.