The part numbers for the 03-04 and 04.5-07 is the same, and I have talked to several cam builders who say they are the same.
The cam has a very tight LSA, and a short exhaust duration. This action is known as incylinder EGR, simply it opens early, and closes earlier to keep exhaust in the cylinder, and to keep the cat hot (this and the timing are why the 04.5+ trucks run so hot).
The OEM cam isn't as efficient as other cams due to the EGR effect. It also doesn't spool turbos as fast as it could due to the shorter duration (shortest duration of any CTD in a Dodge). The second part of the in-cylinder EGR is the piston bowl design on the 04.5-07's.
On stock tuning an aftermarket cam doesn't make a noticeable change in max power, it just allows it to come on sooner. On heavily fueled motors you will see a bit of a difference due to the restriction of the OE cam.
I recently had a Cold Cams Stage 1 put in my trucki ts the mildest cam sold (Same as PDR cam, and Hamilton 175/206), so the effects aren't huge, but they are quite noticable. The exhaust lift/duration is actually the same as a stock 2nd gen, but thats 7.8% more duration than stock, and the intake is 7.4% more duration and 6% more life than stock. The lobe separtion is also drastically changed, which in itself means much cleaner air as the lobe sep on a 3rd gen cam creates an EGR effect (and this was the main reason I did a cam swap).
The differences it made were a stronger feeling bottom end, the turbo spools a bit faster in the 0-25 psi range, 25-30 psi is the same, and 33-35 is easier to obtain. 30 psi of boost is obtained at the same rpms, 1950; but consider 30psi with the cam is a lot more air than 30psi with the stock cam.. so there is much more air to the cylinders much sooner.
The EGT drop isn't huge at high boost levels, but a lot of that is the 9cm housing on the OE turbo. I see a larger peak boost EGT drop stock than with the Smarty tuning. But I would say the 100* EGT drop I reported is mostly from the cam, the intake mods don't do as much at higher rpms/boost as they do in the mid range. And really any EGT drop is great, as I am letting more exhaust out of the cylinder, and the EGR effect is gone, so thats even more hot air coming out.
My next plan is a turbo, either a 62/65/12 or a VGT.. but probably a 62.
Cam's aren't cheap, but its a worthy mod.. now if I could just find the excuse to go on a road-trip to check the mileage. But cruise boost actually seems a little lower (again less boost for the same air), but that should help mileage.
If someone was after a large change from a cam I suggest the bigstick, not the bottom end cam.
Bottom line, if the engine is torn apart I would cam a 3rd gen.. If its not, it all depends on what you want out of it.
At high boost the drive pressure most likely is a bit more than boost but that will most likely be at higher RPM. At mid to upper RPMs the velocity of the exhaust gasses leaving the cylinder and the inrush of fresh air won't leave much chance of reverse flow before the exhaust valve shuts. Now if you had a cam that was too much retarded or too much overlap you could possably get reverse flow and a poorly running motor with no power. But gas motors with non boosted charge air like over lap and retarded cam timing at very high RPMs. "7000-9000"
Billy
On a stock 3rd gen the DP is 2:1 if you disable the WG from about 1500 rpms up. Even not WOT the DP is 1.2-1.5:1.
And your not reversing flow, your simply closing the exhaust valve early and trapping it in there.
It happens, accept it. How else do you think Dodge was able to meet 04.5 emissions without an external EGR?
