[DavidBoren]

Can you please explain why you think that my proposed undersquare 359" six liter motor would be worse than a 364" oversquare six liter motor, when all things are equal other than architecture?

Surely 5ci of displacement isn't going to be noticeable. And if everything else is the same, from the air filter to the rear tires... The ONLY difference is the LS2 achieves its 364 cubic inches with an oversquare bore/ stroke ratio, and "my" engine gets its 359 cubic inches via undersquare architecture.

Why do you feel that the undersquare architecture would be a detriment across the board? I'm pretty sure that the 5.3 and the LS2 both have heads based on the same casting. So if head flow is equal. Displacement is equal. And redlines are equal. Same accessories. Same cam. Why would "my" engine lose power everywhere?

If anything, worst case scenario, wouldn't it just be the same as a LS2? Why and how would I possibly make it worse?

What, exactly, are you referring to when you say "if it will fit"?

If you are referring to the intake valve size, yes, a 2.04" intake valve will fit. Yes, it will be shrouded in the 3.78" bore. Will ported 5.3 heads outflow, or AT LEAST flow as well as, stock LS2 heads even with shrouded valves? Yes.

I don't have to get the stage two porting. For the same price as TEA's porting services, I can get some trick flow heads. And they are meant for the 5.3L, or at least made for the 3.78" bore, and they have 2" intake valves.

No matter what, I can get at least as much air flow as stock LS2 heads. Given that the 5.3 is a truck motor, I'm guessing that GM already has done what needs to be done to make the 5.3 heads flow for best truck-like torquey performance.

Am I absolutely missing something? The way I see it is that it is fairly impossible for me to mess this up. "Failure" for this project is 400hp and 400ft/lb of torque. That's what LS2 parts on a six liter air pump produces.

Air flow determines redline. Redline determines cam. Cam determines how your engine uses the air flow up to the redline. Right?

So if I have a six liter motor with enough head flow to support the same redline as the LS2, and I am using the same cam, then at the very least I should expect to see the same result at redline... Regardless of whether the air pump is over or under square.

Now, I personally think that I will actually see an increase, everywhere. Let's say that the added mechanical leverage provided by the 4" stroke only adds 25ft/lb of torque, 500rpms sooner. Everything past that point will be higher than the same rpms on a LS2. Why?

Horsepower is a function of torque. Increasing mechanical leverage to increase torque will inherently increase horsepower with it.

Let's say that the LS2 cam is capable of climbing five stairs. In the stock application and configuration, the last step is at 400hp and 400ft/lb of torque.

But my 4" crank six liter motor gave us 25ft/lb extra, so the same cam climbing the same number of stairs reaches 425...

Assuming you can follow my analogy comparing useable powerband to a flight of stairs.

After all, an engine is nothing but an air pump. The fact that we choose to add fuel to and then burn the air, as we pump it, does not change the fact that an engine's primary function is to move air.

The amount of air the pump can move determines how much fuel can be added. Things like compression ratios and the timing of ignition events all determine how much power that amount of fuel, in that amount of air, can or will produce.

However, you can change how that power is transmitted from the pump to the ground. Things like mechanical leverage are dumb. Dumb in the sense that mechanical leverage exists without any air being pumped. Increasing the length of a lever increases torque. The end.

So, all other things being equal, increasing the stroke from 3.6" to 4" has to produce an increase in torque... Does it not?

And if you increase torque anywhere, any earlier, then all numbers after that point will be higher, because horsepower is a function of torque. So if you take it to the same redline, then theoretically, there's no way for the end result to be lower.