I have a 97 4.6 and I was woundering how much more power ya'll think I could get out of my 4.6 with new
Throttle Body
Intake manifold (is there anything to gain with this?)
and Headers?

 

My guess is maybe 8 - 10 hp on the top end.

Your 97 is like mine...non-PI heads. They just don't flow very well. Opening up the t-body and exhaust may help a little, but the bottleneck is in the heads themselves.

If you are gonna go through the trouble of putting a new intake mainfold on, you may as well swap to PI heads and use the PI intake manifold as well. This will give you nice gain, from both the increase in flow and the increase in compression ratio that you'll get. BTW, I'm not aware of any performance intake manifolds for these engines, besides going the PI route.

But if you have to pay for labor, then this could get expensive, approaching supercharger-type of money (that's the route I took).

I don't think the t-body is really that restrictive...same with the exhaust manofolds. I run the factory t-body and manifolds, and I make as much power as any other non-PI, blown 5.4L out there (admittedly, there are few!).

Lots of folks do the PI head/intake manifold swap, and report good gains.

 

Pi heads will only produce 11hp.Remember the increase from the 98 to 2000 was 220hp to 231hp with the new heads and cops.You must have forced induction for any of these mods to really matter.I would not bother.The best bang for the buck by far will be gears.

 

Putting PI heads onto a non-PI truck ups the compression ratio due to the differently-shaped combustion chambers and piston tops. Higher than the PI motors.

You'll see 10.5:1, which is pretty high. And if you do the head swap and later decide to run a blower, you need to use thicker head gaskets to lower your compression ratio to around 9.5:1 or so.

Mustang guys report anywhere from 34hp to almost 60 (if you get some head work done before you put them on) on their 4.6 motors.

So the increase is a bit more than just comparing the factory ratings for PI vs. non-PI.

But I agree that it is a lot of work for minimal gain. If you do it your self, it may be worth it. But not if you are paying for labor.

 

The aftermarket intake manifolds for the trucks are non-existant anyway... you'd have to swap in a Mustang manifold. Their intake placement is on the opposite side of the engine compartment and require a different plenum turned towards the passenger side. A bit of work for a few ponies and it'll tend to push any gains higher in the rpm band.... the intake was geared more for a car than a truck, so go figure.

-Kerry