Originally Posted by siggyfreud

The amount of fuel you need is dictated by the amount of air the engine can bring in. Simply adding more fuel isn't going to give you more power, unless, for example, you're running lean enough that you're being robbed of power. If you do some datalogging via your tuner, or on a dyno, you'll be able to see what your injectors' duty cycle is at. Duty cycles range from 0%-100%. 0% means the injector is open 0% of the time. 100% means the injector is firing all the time to keep up with the fuel needed. In my experience, I haven't looked to bigger injectors until my duty cycle began peaking above 80%.

All the injectors are is a spout. You can control fuel two ways. The amount it flows, and how long it's open. So if you can't keep the injector open longer to flow more fuel (because it's nearly open all the time anyways), THEN you've reached the point where you need to flow more during the time it's open.

Once you determine where your injectors are at, then you'll know what you need. Given your mods, I'd venture to say you're not at the point of needing new injectors yet.

Same goes for fuel rails. They might look pretty, but you won't need them for awhile. As a point of reference, I ran nearly 500hp at the wheels on my stroked 4.6l, and it ran on stock fuel rails and 39lb injectors (but probably getting close to the point of needing 60lb).

Originally Posted by DTMR

Okay cool but why about after i do heads? Im planning on getting frpp heads too

Originally Posted by breathegood

Even with heads, you aren't likely to need larger injectors. I get plenty of fuel for the volume of air that my setup [see sig] will flow. Even with a TB, intake manifold, and O/R long tube headers, I suspect the stock injectors would still do just fine for a N/A 4.6L with stock bottom end.