03 BLACKOUTSSS

iTrader: (3)

Thinking about changing my cam from this

218*/214* .581"/.581"

to this

220*/218* .563"/.590"
The intake lobe is Comp Xtreme High Lift and the exhaust lobe is a Comp XER. I think that the still relatively short duration will make it a good setup for a TB converter, and the fast ramp rate of the exhaust lobe will assist in generating vacuum in the cylinder, and help to "suck" in more fuel and air. Can someone tell me if I am on the right track, or if I am out of my mind.

I am trying to keep my DCR on the high side, as I am running N/A. My question is what LSA and ICL combination do you guys recommend for a nice broad TQ curve.

04Crew

I'm no guru but I'll take a shot since no one else has. Compared to your current cam holding the exhaust valve open later in the cycle (with the larger duration lobe) will help create vacuum. However, that can't do much if the intake valve is still barely open. So to get the effect you are looking for, you would need to tighten up your LSA and also stay with a faster intake ramp.

That said, what are you trying to accomplish versus the cam you have now? Those lobes are so similar to your current ones that you probably won't see much difference unless you change your LSA and/or advance by 2-3 degrees (which can have other trade-offs such as idle quality, fuel mileage, etc.)

Lastly, why the decrease in lift on the intake (versus your current cam)? Your ported heads should flow well above .570.

03 BLACKOUTSSS

iTrader: (3)

Well, I figured that with the duration at 220 on the intake and the lower lift, it would still get about the same fuel/air that I am getting at 218 duration and 581 lift. What I am really looking for is the tq to come in hard as early as possible. Plus with a little more duration, and vacuum being generated from the exhaust lobe, that would provide more time to increase air velocity and help in raising my VE (I hope I am using that term correctly). Maybe a fast opening and slow to close intake lobe would be beneficial for maximizing airspeed through the port? Is there a lobe profile that isn't symetrical like that? I'll have to get a hold of Lloyd Elloitt and see if I can get the flow #s for his stage 1 317s.

03 BLACKOUTSSS

iTrader: (3)

Another question, wouldn't tightening the LSA increase the overlap and decrease DCR? If that is right, which one is better, a higher DCR or a tight LSA to generate that sucking effect?

03 BLACKOUTSSS

iTrader: (3)

To clarify, which one is better for making power?