Valve lift VS. Port velocity question.

EHardy1971 · 10-06-2009, 04:12 PM

Ok guys, most of you know I'm running GT40 Irons on my car, with the E303 cam (set @ 4* ADV), and the Crane/Cobra 1.7 RR's. When I went with the 1.7's, I understandably lost a tiny bit of bottom end torque due to changing the powerband of the cam. I know as valve lift increases, port velocity decreases. According to this, the GT40's make power all the way up to .600" of lift.http://www.allfordmustangs.com/Detailed/630.shtml However, they don't make THAT much more at .600" than they do at .500". Do you think the 1.7's are hurting me more than they're helping? I know bigger isn't always better in some cases.

When I dynoed it a couple of months ago, it made power up to 5200 RPM's, which I know is mostly the intake.

SilverBack · 10-06-2009, 04:16 PM

You also have to consider that changing the rocker ratio effectively changes the opening & closing event timing, not just the maximum lift at the valve.

EHardy1971 · 10-06-2009, 04:56 PM

Quote:

Originally Posted by SilverBack

You also have to consider that changing the rocker ratio effectively changes the opening & closing event timing, not just the maximum lift at the valve.

It also increases the duration IOW.

SilverBack · 10-06-2009, 05:44 PM

Quote:

Originally Posted by EHardy1971

It also increases the duration IOW.

Yep, I guess that's what I was getting at. The opening and closing happen faster. You've basically got a "bigger" cam than with the 1.6s and shifted your torque curve later in rpm range, possibly losing some down low.

How does it feel in the higher rpms?

EHardy1971 · 10-06-2009, 05:51 PM

Feels plenty strong and torquey from around 2400 and up.

89five0Gt · 10-06-2009, 07:12 PM

Quote:

Originally Posted by EHardy1971

Feels plenty strong and torquey from around 2400 and up.

If it don't have enough torque, then put a bigger shot on it

QWKSNKE · 10-06-2009, 09:03 PM

Doesn't the 4 degrees cam advance you have bring the powerband back down or am I thinking backwards

EHardy1971 · 10-06-2009, 09:49 PM

Quote:

Originally Posted by QWKSNKE

Doesn't the 4 degrees cam advance you have bring the powerband back down or am I thinking backwards

No, you're right. I was planning on putting it back at 0* awhile back, but since the Explorer intake drops off after 5200 anyway, I decided to leave it alone.

itlepeanut · 10-06-2009, 10:08 PM

Quote:

Originally Posted by 89five0Gt

If it don't have enough torque, then put a bigger shot on it

Are we gonna see what kind of "shot" you have at trackday this year?

coupe · 10-06-2009, 10:16 PM

Not much more you can get out of a 220º duration cam (E303). If you wanna really benefit, put some more camshaft in it. I wouldn't hesitate to go somewhere around 228º duration, but I wouldn't mess with anymore than about .500 lift on the heads.

As for your question, the 1.7's are not hindering the E303 on your combo.

10-06-2009, 04:12 PM	#1
EHardy1971 Trunk Monkey Join Date: Jun 2007 Location: Home Posts: 5,708	Valve lift VS. Port velocity question. Ok guys, most of you know I'm running GT40 Irons on my car, with the E303 cam (set @ 4* ADV), and the Crane/Cobra 1.7 RR's. When I went with the 1.7's, I understandably lost a tiny bit of bottom end torque due to changing the powerband of the cam. I know as valve lift increases, port velocity decreases. According to this, the GT40's make power all the way up to .600" of lift.http://www.allfordmustangs.com/Detailed/630.shtml However, they don't make THAT much more at .600" than they do at .500". Do you think the 1.7's are hurting me more than they're helping? I know bigger isn't always better in some cases. When I dynoed it a couple of months ago, it made power up to 5200 RPM's, which I know is mostly the intake. __________________ Eric 89 LX Coupe-Juiced 01 Lightning-Boost 06 TBSS

10-06-2009, 05:51 PM	#5
EHardy1971 Trunk Monkey Join Date: Jun 2007 Location: Home Posts: 5,708	Feels plenty strong and torquey from around 2400 and up. __________________ Eric 89 LX Coupe-Juiced 01 Lightning-Boost 06 TBSS

10-06-2009, 09:03 PM	#7
QWKSNKE 3v's are slow Join Date: Dec 2004 Location: Here and There Posts: 17,152	Doesn't the 4 degrees cam advance you have bring the powerband back down or am I thinking backwards __________________ 2009 Porsche Carrera S 2008 ///AMG C63.. Eurocharge Tune. RIP 2019 AMG GLC43..wife's 03 F250 SD.. Edge Evo, AFE Stage 1 CAI 08 GT. JBA axle back, FRPP springs, FRPP swaybars.. daughter's 01 Cobra vert... wife's I need a new toy

10-06-2009, 10:16 PM	#10
coupe Super Moderator Join Date: Dec 2004 Posts: 6,313	Not much more you can get out of a 220º duration cam (E303). If you wanna really benefit, put some more camshaft in it. I wouldn't hesitate to go somewhere around 228º duration, but I wouldn't mess with anymore than about .500 lift on the heads. As for your question, the 1.7's are not hindering the E303 on your combo. __________________ " If you can't explain it simply, you don't understand it well enough. " - Albert Einstein

10-06-2009, 04:16 PM	#2
SilverBack Senior Member Join Date: Jun 2008 Location: Pell City, AL Posts: 418	You also have to consider that changing the rocker ratio effectively changes the opening & closing event timing, not just the maximum lift at the valve.