I just bought a 91 f250 with the 5.0 and a 4 speed.. it has a lil bit of power but I want more. chain to chain my buddy's 87 chevy drags me in circles and I never hear the end of it. Yeah my truck has enough power to tow the things i need to, but everybody loves more power! I'm lookin to get somewhere around 300 hp and 400 ft lbs... what can I do? I'm already planning on a more open intake and better flowing exhaust... but that won't bring me up that high. Can i screw with the ECU to push more fuel outta the injectors? will mustang 5.0 parts match up? I'll do pretty much anything shy of a complete rebuild.

 

Any intake you buy will be a waste of cash, just get the lower tube, the one that goes from the radiator support to the filter box, off ether a 4.9L (inline six) or 7.5L truck. The rest of the factory system is more than large enough for the 5.0, hell most of it is used in trucks that have bigger engines.
Next do a tune up, spark plugs (autolites of motorcraft coppers will do doesn't need to be fancy gaped .046in), spark plug wires (ford racing 9mm), and MSD blaster coil for the TFI fords. After doing that grab a timing light and pull the spout and set you timing at 13BTC; remember to put the spout back in place. Now take your truck out for a spin, have the radio off and listen for what sounds like empty piant spray can rattling while your driving; if you hear it pull the spout out again and set the timing at 12BTC. So on and so fort till you no longer hear the rattle can.
The exhaust on these trucks SUCK bad, but the worst parts are the exhaust manifolds, Y pipe and the cat, both of them. If you can replace the manifolds with long tube headers, have a custom Y made and get a high flow cat you will be set.
Messing with the ECM isn't needed for more fuel flow, but due to the heads and cam in these trucks the engine can't even use the amount of fuel the injectors could release. Just put it this way, the ECM, fuel regulator, and fuel injectors could support an engine producing over 350HP, with out any changes.
Most mustang 5.0 parts will fit the truck motors.

About your buddy yanking your *** all over the place, not knowing the weight of his truck, whether or not ether of you have locking diffs, and how good of a driver ether of you are. I say, trow a ton of crap in the back of your truck and hold the brakes while reving your engine to 2200RPMS and when his truck starts bruning tires, let off the brake. (use the parking brake, no taillights)

 

The short answer here is you got too much truck and not enough motor. Yes the 5.0 can be improved quite a bit from what you have but you won't get anywhere near 400 tq from it without a supercharger. The right thing to do here would be to swap in a 5.8 with a few minor upgrades like a cam and full exhaust system. Those things on the 5.0 could make as much as 275hp depending upon the cam with no changes to the fuel or EFI system, which is 100hp gain over stock so it's not a subtle change, but all that extra power comes at higher rpms with little or no increase at lower rpms and maybe even some losses, but that's the nature of the 5.0.

 

I am waitin for someone to scream and yell at him for doing a tug of war with his truck

 

Me too
And thanks everyone else for the tips. I wasn't planning on a whole different intake I was thinking bout a conical filter I saw with 2 holes specifically for the intake hoses
I also found this
[1) Remove air intake muffler inside the right front fender and install a K&N panel filer in the stock air filter box. Do not make the mistake everyone makes by putting a big cone filter inside the hot engine compartment. Removing the intake muffler assembly will free up some of the intake restriction. Using the panel filter will allow cool dense air, outside the engine compartment, to make its way to the cylinders.

2) Consider swapping out the 1.6 ratio rocker arms for good quality 1.7 ratio rocker arms to open the valves more and let more of that cool dense air in the engine from the first mod. The MAF EFI system will adjust to the greater air flow and compensate with more fuel, so no fuel system mods are needed.

3) Consider a ring and pinion swap. Don't go nuts with the 4.10 and 3.73 ratios most folks do, stay more conservative at 3.55, you will like the boost in power, and fuel economy will not be affected.

4) I do not recommend removing emission controls, catalatic converters are really effective at reducing exhaust emissions so your car is not offensive to drivers following you. In my opinion you won't gain much power from a cat back system, you would spend as much on a 3.55 ring and pinion swap as a good cat back system but you can actually feel the power difference with gears.

5) Don't be afraid to crank in a few more degrees of ignition timing 13 or 14 degrees generally won't cause ping or knock unless the engine is hot. A 180-degree thermostat would help keep the engine temps down for a little extra performance and give extra insurance against knock and ping with advanced timing. Don't go below 180 though or risk the PCM not going closed loop and engine check light being on.

6) I recommend staying away form the power chips for the PCM, fuel economy will suffer, premium fuel can be required and performance won't be that great for the cost, especially for on-going fuel costs.

7) Removing the AC is only weight reduction and not much else. When the AC is turned off, it is the same thing as using an AC pully eliminator. The smog pump removal will net you less than one horsepower gain, the catalytic converter won't get the air they need to work properly without the smog pump too.] From this website-http://foxbodyforum.com/5-0-performa...s-for-the-5-0/
What do you think about the rocker arms and diff ratio? Also I read somewhere about E7 heads?

 

I'd say get headers and get a custom exhaust from there. Also if you really want to dive into the engine there are a few computer compatible cams.When you say four speed I'm going to assume manual. Why can't you drop it into granny? I've ALMOST been pulled by a buddies I6 because he had a granny gear.

 

Doesn't exist on a '91 ford truck.. so don't bother looking for it.

Good suggestion

Another good idea unless you're changing the cam.

Again.. doesn't exist on a '91 Ford truck.

Great idea but ignore all that crap about not going wild, a 5.0 needs 4.10 gears minimum even with stock sizes tires.

Agreed.. except that I would recommend substituting the stock Cat for an aftermarket version.

Yep most engines will take 2-4 degrees more advance with no ill effects... free power.

This will work too especially of you live in a hot climate.

+100.. complete waste of time.

Yep... wasting your time unless the smog pump is seized.

 

this was very helpfull. and a few things baout my truck... taillights dont work so as far as holding the brakes that will be fine lol but also when I bought the truck the exhuast had already been cut right off the end of the Y pipe.. there's no emissions stuff where I live so cats aren't required. I'm thinkin headers and stright pipe it with side pipes.... maybe cherry bombs. Money isn't really an issue for me but I'd like to keep things as cheap as possible. I already looked up headers from NPD and they want like 500 bucks... I'm almost considering droppin a 5.8 in it and throwin the 5.0 in my Mercury Capri lol

 

Sorry but I'm calling BS. There is no way a stock 19 lb per hour injector can support 350 HP even at 100% duty cycle unless you raised the pressure at the rails to like 63 PSI, and by doing that you'd be taking the stock regulator out of the equation.

I built a Mustang and it's probably sitting at 330-340 at the crank and I had to upgrade my fuel system to a 190 LPH pump, BBK adjustable fuel pressure regulator, and 24 lb per hour injectors. And even with my 24 lb injectors my duty cycle is still a little on the high side.

Oh and here's a little bit of info floating around the web
"Injector HP ratings: divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI."