Best way to extend the power - lift or duration?

[MadBill]

...PM says I'm at .55 intake mach z-factor but I'm not positive what that means. I don't think PM says anything about CSA. It does say that the intake curtain area is too small for 6500 rpm.
I do know the CSA at the intake gasket is about 2.80 sq inches which is small for 470 cubic inches. If I plug it into the choke calculators it tells me that the engine will choke at 6600 rpm. ..

About 1/3rd of the way down the dyno results page, PM shows port velocities with various average CSAs and zeros in on recommended values.

[andyf]

Ahh, you are correct. Guess I forgot about that section. For my engine is says 285 FPS at 2.80 CSA which is the smallest recommended CSA. Looks like PM is recommending a 3.050 CSA for this combination which would require a little bit of carving.

[F1Fever]

From what I can tell, with regards to cam only is open the exhaust earlier.
Next is Close it later split nearly equally with a later intake close.

[MaxFlow]

Depends on whether you are pulling the port turbulent or not. Once against the velocity wall you are limited to what a cam can do. I'll take a head that has a kick ass velocity profile and makes as high a cfm/hp as imaginable. Compute that back and determine whether duration is going to help or hurt. Most of the time duration won't even do anything without the cylinder pressure to make it work.

I'd rather have lift if the port is "RIGHT"...........and that can only do so much because of bumping against the pump. That's why area through BDC is more important on engines with good heads.

Randy331's 383 was a prime example if you go back and read through that thread.

[F-BIRD'88]

For the stuff I do duration and timeing event points are much more important than lift.

When and when and when is very important. Duration is between when and when.

When matters when when and whwn get progressovly shorter by added rpm..

[hoffman900]

We see this all the time in rules restricted road race engines...

Develop a really great header utilizing all the principals Calvin Elston preaches. Then keep feeding more intake duration into it. The header will protect the bottom and mid range and the cam will extend power up top. Power curve will typically peak in the same place (because of restrictions on porting / valve size / lift) but the power will hold quite a bit longer.

Restrictor plate engines run the same way... well past the point where they are choked.