Madhatter wrote:
I went with a different tack on this build early on, I think we may have talked about this off-line Mark. Given that flow numbers are not the best by conventional stds I spent way way more time then I figured it would take to approach it from a dynamic flow model, as in my opinion that's closer to how an engine operates in the real world. So by utilizing the wave model and then focusing on simulated CFD analysis I went about trying to design the best cam lobe profile to get the most power out of this build. Man what a PITA time consuming project that turned into, though it was not for naught. The real fun started when I had to then get a master made so an actual grind could be done. Laurie at Webcam was an invaluable help with that.
We did chat and really peak flow isn't all the telling. A head with weakish very low lift flow but strong mid lift before it's choked by the manifold at high lift, coupled with a aggressive ramp longish duration cam can make a good power curve and decent peak. This is the theory that can lead to the classic "over cammed" low to midrange pig if a ton of care isn't taken and it will never do as well for peak or midrange as a head/manifold combination with good seat velocity at all lifts coupled with a more moderate duration cam with aggressive ramps....but it can be made to work well.
I didn't love any of the cam options I found for my engine either particularly for exhaust but wasn't willing to invest the time to do custom lobes. On the 3.4 setup I had to stay shim over so lift and performance with it were limited quite a bit by that constraint....higher lift shim under would have added a over 30hp and more aggressive porting on the head at the expense of seat velocity would have added another 20-30 to the peak I think....so closing on the estimates for the 4.0 but not there....but as I said I have a bad habit of sticking to the map and looking for good seat velocity at all lifts and calling development done when I hit a flow limit somewhere.
Madhatter wrote:
Sorry its' a PDF guys.
You can zip it and attach or snip it and post as a picture.
Edit...you did while I was typing
Yes, one you make more torque the gear ratios are very unhelpful. I used to start from 2nd gear most of the time with the last blower engine I had.