Dyno simulation, cams for GT40P'd 306

[Capri306]

First off, let me state that I realize that this exercise is only a simulation. It's only here for comparison purposes and should in no way reflect real-life situations. Boy, that sounds like the warning they state before "Jackass" huh?

I've been doing some research over the past week or so trying to find the best OFF-THE-SHELF camshaft for my GT40P headed 306 project. There have been as many suggestions as there are camshafts available! Please keep in mind that I really don't have the money right now for a custom cam, otherwise that's the way I'd go.

Anyhow, just to bring everyone up to speed on my little project, here's the plan: 306 (5.0L overbored 0.030-in), ~10.35:1 compression, TRW forged flat-top pistons, factory rods and crankshaft, GT40P cylinder heads w/ only a mild port cleanup and shaving, roller rockers, full-length headers, Exploder intake, 65mm TB, ~3000rpm stall through a Lentech-valve-bodied AOD. Everything else I'm considering superfluous at the moment. The notch already has 3.73 gears and full exhaust, with MAF conversion (1989 A9P EEC-IV), and an MSD box.

On to the sim!!! The attachment is part of the output graph. I compared Trick Flow Stage 1, Crane Cams' 2031 (requires 1.7 rockers), and FRPP's old E303 (which I currently own). I put everything into the simulation with some correction factors I thought were important, namely the size of the valves. It's beyond me why they ask the size of the valves if you already have an airflow file generated. I used the airflow numbers that StangPro.com has posted on their GT40P article. The intake flow numbers I used in the simulation were high (1100cfm, Sequential Injection manifold), but this was done to eliminate the intake as a restriction in this simulation. I realize that the real intake is going to limit the available air to the combustion chambers and intake ports.

Worth pointing out:
1. No matter the camshaft, torque falls off at or shortly after ~5000rpm.
2. The highest-horsepower camshaft (Crane 2031) is lagging torque in what would be considered the "normal driving" RPM range, but only by about 50 lb-ft.
3. Even though the Crane has the highest horsepower, for an unmodified EEC-IV, that RPM wouldn't even be possible. Although in this simulation, it keeps climbing on up to the rev limit for a peak of ~475 HP.
4. Horsepower of the Crane cam is also below the others until approximately 5000 RPM, but again not by much.

It's all a tradeoff. It seems like sticking with the E-cam I already own is my best bet, and spending the money on another would just be a waste. My biggest problem with the E303 is that is just wouldn't work with my 2000 stall converter, but that's no longer going to be the case. I don't think the Crane is worth it since there's such a drop in torque for so little gain (for me) in the top end. This is going to be a daily driven vehicle, so I'm trying to keep as flat and high a torque curve as possible.

Any thoughts or suggestions???

[HoodStrype]

Don't mean to change the subject to heads, but I was thinking about trying to find a set of GT40P's... are they that powerful? I know this thing has a cam and an Exploder intake. What do those puppies run $ wise? Cool comparison too, thanks!

[red82gt]

Keep the E303 until you can afford something custom. For GT-40P's you'll need more duration than those choices offer but you won't need a whole lot of lift.

[Capri306]

I'm thinking this is likely true, which is why I'm going to run a p/n 35-351-8 CompCams profile tomorrow after class. Hopefully it'll verify this. It's just too bad you can't load a cam profile in more detail in Dyno2k, especially one with different ramp rates.

Oh, and if I didn't mention it a couple years ago when the notch's AOD finally popped, the timing chain was going bad as well. How far does it have to be worn so that an E303 will idle smoothly as the factory cam?

[Capri306]

UPDATE: The XE274HR showed no improvement whatsoever over any of the forementioned camshafts, at least on my simulation. In fact, the shape of the torque curve is like the E303, but about 5% LOWER across the entire band.

See the attachment.

Again, it's hard to tell for sure without knowing the exact profile of the camshaft, but I think my simulations have shown the limits for unported GT40P heads. A cleanup of the ports may well be justified; I will attempt to find reliable flow numbers and try the simulation again. Stay tuned.

[rwhite65]

Capri-
When I was picking a cam this summer, the guys even thought I shoulda bought a custom cam, and u have better heads then me. But, the direction the car will be going in the future is way better heads then the current ones, so If I was gonna order a cam, I would want it to be cut for a much more radical motor then this one. I tried to find a buddy with an e-303 but with no luck, so I bought the stage 1 trick flow. For the price, I like it, pulls nicely. I wish I had some dyno or track numbers for you, but I have not been able to get to either facilities lately.
Personally, if there was not much difference in the cams from ur e-303 now, I would wait and see where u want to go in the future. Kinda a pain, but no biggie to switch it down the road if u decide to. Good luck, and if I get to the dyno, I will let you know what I get for power out of this combo.
Ryan

[Capri306]

Thanks, Ryan. I'd be very interested to see what kind of numbers your setup can put down, and particularly the torque curve's shape and level across the RPM range. I think I'm too much of a chicken to put any of my own babies onto a dyno. At this point, the E303 is staying because it's just too little of a gain to buy a new cam. I'm looking into spending the money on a timing set that won't wear out as quickly as this last one did, though. The thought of a gear drive has definitely crossed my mind.

[Jeff Chambers]

Stay away from a gear drive; nothing but noise and trouble. If you want real clean timing, go with a belt drive. Australian Muscle Parts makes a killer belt drive for about half the cost of others.

Try this cam, 239/244 @ .050, 110 LSA, .312/.312 lobe lift. This cam made 465hp with unported P-heads for me and 535hp with TFS TW heads. Both were using a Stealth intake and 650cfm carburetor.