First you need to ask at what psi the number is derived at. The two standards are 25 and 28 psi and there is a difference. If memory serves me correct the stock heads flow about 260 cfm at 28 psi.

 

Markski,

I just noticed I'm talking too much. This is your thread. I apologize ........... bye.

 

ya but it's good info

 

here is the difference:

 

Markski great pictures and glad you made it home safe

 

My valves are in between stock and GT3 spec . . . 39 mm intake and 34 mm exhaust (made by Ferrea).

My heads flow 324 cfm at 28 inches of water.

I suspect Markski's heads flow north of 350 cfm (perhaps well north).

Its all about head work!!!

Craig

 

Craig,

Just as a comparison, our heads flow tested at 362 cfm @ 25 psi. If you convert to 28 psi they would flow additional cfm's.

 

All I know is that Todd said that these heads he got were the neatest things he has seen in a long time...
I just took it out and OMG- bet. 2 to 3K this thing has so much TQ...
The 996 naturally aspirate cars have the same effect and produce
great low speed torque due to that. The camshaft actually follows the
throttle plate. As you press it down, it advances the cam for that nice
torquey feel, then as the rpms climb, it retards them for the high rpm power stuff...

markski

 

I am a bit confused Chad. On April 25, 2006, you posted that your heads flowed 327 cfm at 25 inches of water: https://www.6speedonline.com/forums/...97&postcount=5 . Now you post that your heads flow 362 cfm at 25 psi (I assume that is the same as 25 inches of water). Have you ported your heads further in the interim and/or further increased the size of your valves?

Craig

 

Very exciting Markski. Your car is a tremendous accomplishment!!!!!

Craig

 

Unfortunately I'm not really that savvy when it comes to this kind of work... I can only imagine the complexity that goes into our motors.... I'm sure I only touched the surface if this tuning stuff... all I can say is WOW...
thanks Craig,
markski

 

Craig,

The final cam grid exceeds the .550 lift that we tested back then (July 2006). In addition, those July tests were done with NA durations, the durations are now profiled for a turbo motor. This is where the additional flow is derrived. The port configeration has not changed other than mild touch up on the intake ports and micro polishing the combustion chambers.

 

Lol! On the scale of savvyness relating to our motors, you possess a PhD compared to my thimble full of knowledge.

Craig

 

I wish... I only paraphrase The Mad Scientist... LOL

here is what Todd came up with theoretically at 14 psi vs actual. Looks like, according to him, that the dip is not that much of a dip between 5.5 to 6.5 k as the the huge bump at 5K rpms... we only have a small flat spot at 7K. he says that can be messaged out with dyno time...

 

So your previous 327 cfm measurement was at 550 lift? My 324 cfm measurement was at 500 lift. I do not know how much more cfm my heads would flow at 550, as compared to 500 (assuming I can attain 550 lift) (probably not much more). What lift did you use for your 362 cfm measurement?

This points out the problem in comparing head flow numbers. The parameters must be consistent.

Craig