I have a 97 f150 with the 5.4 and I am going to do the MHS stage 1 pi head swap and stage 2 cam setup. I am also going to get a HPS intake, BBK 78mm throttle body, 90mm MAF, forged rods, and forged 3cc pistons. I know I will need bigger injectors with this setup and I am wondering what size would be the best. Could I use 24lb injectors or should I use 30lb injectors and will i need a different fuel pump when I get one of these bigger injectors? Any additional info will be appreciated.

Thanks,
ccdline73

 

you can feed 24#ers up to about 5,000rpms...



might as well do the twin 255's

 

Should I go with the 24lb inj and stock fuel pump?

 

I don't know, I can't see thru the internet at your combo and RPM range, hence why I stated what I did in my previous post...

 

Excerpted from the Ford Racing Performance Parts catalog ...



Fuel pump information may be glimmered from the same catalog in the PROPERLY SELECTING ELECTRONIC FUEL INJECTION COMPONENTS section.
.

 

What are twin 255s?

 

As the chart indicates injector sizing is by hp at a specified pressure and flow rate, not rpm.
A 255 liter per hour (Lph) pump is plenty for at least 400 hp.
Twin 255s is way over kill for a street motor but won't hurt.
Never get the pump capacity so high that there is a danger of blowing the fuel line or hanging the injectors open to long at high rpm from the excess pressure.
To size injectors and fuel pump capacity you need to estimate somewhat accurately the expected hp level of all the final mods, then select the injector size to feed that amount of power.
There is more to know about injector sizing such as the 85% rateing.
Normally at idle the injecotor has to flow at least 5% of rating or the flow is not reliable for a decent idle.
Larger injectors not reprorgramed for will close down to far at idle and may cause start and idle issues.
At 85% flow, this insures the motor will not run lean at end rpm so the 15% safety margin. You can run beyond the 85% and get away with it but if the motor hits the ceiling for fuel delivery, goes lean, it puts the motor in jepordy.
With the changes you are wanting to do, I would engage the services of an experienced shop in these type mods and dyno tune it.
If you lay out all the money and labor and lose it for lack of tuning and correct setup/drivability issues you will whished you did.
Good luck.

 

I've been told that I should be expecting 325 to 360hp so I guess I should go with the 30lb injectors for safety. What's a good cheaper brand for a pump? And do I have to get a regulator to adjust the fuel pressure?

Thanks,
Ccdline73

 

You already have a regulator on the fuel rail.
I made reference to high pressure because some jerks put the pumps in series.
In parellel the volume is doubled but not the pressure.
It's volume you need to have.
30 lb / hour is about perfect for the estimate.
The fuel mapping and ignition mapping should be worked out on a dyno unless the builder has done the combo before and knows what program changes to make..
He has to make the injectors and Mass Air track each other closely for A/F ratios and load changes.
There is more to all this than just assembling parts and go.
Good luck.

 

I have access to a dyno so tuning won't be a problem. What pump should I go with?

 

I have a clean set of 24lbers I bought from terajerame that I did not end up using...let me know if you would be interested in them!

 

A single 255 l/h pump should be enough at this power level and RPM.
If you use an adjustable regulator, use it only to trim in the fuel delivery and not to make large flow rate changes because as you raise pressure the flow volume goes down.
It's an inverse function you can't change.
I assume you have the capability to change PCM tables when you say you can use a Dyno in order to tune in the power curve.
If not you can only see what the power is and not change anything.
Important item on the dyno is the use of a wide band OX sensors so you can see what the fuel delivery is doing and stop it if to lean.
And adjust injector pulsewidth and timing for max power.
Be awhere that under max power the system's OX sensors go open loop so you need to take care of open loop tables as well as look at the A/F on a seperate wide band sensors for both banks.
It takes time and understanding what your doing.
Good luck.

 

a single 255 will push way more than enough for him...a single 255 will support a lightning swapped 5.4 running 12lbs of boost with up to around 400rwhp from what ive been told multiple times so a single 255 walbro will be more than he needs and they are only $100.

 

How do you install/setup the walbro pump?

 

Order the kit for our trucks, drop the tank, pull the fuel hat and just replace the pump...it's actually not too bad but you def need a floorjack and some blocks of wood