yurizx6r

Hey guys, I know this is sort of a grey area question that has been asked before, but I was just wondering how much hp I can have before I have to upgrade my fuel injectors. From what I read, the most consistent answer is around 280 hp.

My set up is this: BBK CAI, C&L 73mm MAF, 70mm TB, American Muscle Bama chip, and a full exhaust (long tube, off road H, and flowmasters catback). I would like to put in either an Edelbrock or trick flow intake manifold. Can I do the intake manifold without having to upgrade my fuel injectors? Will this hurt the motor if I do not? I know I have to upgrade when I do heads, but I need to save up more money because when I do the heads I want to redo the entire fuel system, cams, timing chain, etc. etc.

Thanks for any help in advance!

mjr46

you have no real power making mods to warrant anything other than 19's right now

88 orangepeel notch

You'll be fine with 19's, save your money.

I'm at 300 rwhp right now and still running 19's. They are maxed out on duty-cycle at redline, but my wideband shows its not lean so I'm right at the limit. They can take short squirts at max duty cycle, just not long periods like in road racing. I've been running this car for 6 yrs as is and haven't had a problem. Yes, I'll be putting in 24's just for the safety margin. But you'll be fine with 19's.

yurizx6r

Perfect! Thanks! Just curious, how did you get to 300RWHP? I know once I do heads it's a good idea to upgrade, but I don't want to right now if I do not have to.

88 orangepeel notch

I can't take complete credit for this motor, p.o. must have did his homework because it's a basic 306 with all bolt ons, letter cam and ported E7's. When I first bought the car it had a built AOD with a stall, dyno'd 270/300. All I did was swap to a T5, added a fender mount cai, and electric fan. Car then put down 300/316. It shouldn't be making those #'s, but I think it's one of those things where everything is working together. Good luck with yours, they are fun cars to play with.

AMWill

Both of these guys are right on with their advice! The factory 19lb fuel injectors are plenty for this setup. You'll probably be able to use them with aftermarket heads too. However, add a lumpy camshaft to the mix and you should upgrade to the 24lb'ers.

Have fun with your build! These push-rod 5.0's have always been one of my favorite Mustang engines.

Shane

Pontisteve

It's worth mentioning that the 280HP limitation is right on with the typical injector calculation formulas, but that this is 280 gross FWHP, not net, not rear wheel. That's just the engine, on a dyno, with no belt-driven accessories being attached to the engine.

You could exceed the 280 mark, but the duty cycle rises above the desired 80%. Why 80%? Because the injector driver circuit needs time to cool off or it will overheat. And because anything over about 90% doesn't really allow for proper fuel control. And finally, because all of the fuel is supposed to be injected onto the back side of a closed intake valve. At some point, that valve opens, and the fuel would be injected into an open intake valve, which is not ideal for complete atomization.

yurizx6r

Well as it turns out. Today I am picking up an Edelbrock Performer upper and lower intake manifold that comes with 24lbl injectors. So my total engine mods would be CAI, 73mm MAF, 70MM TB, Edelbrock intake manifold, bama chip from American Muscle, and a full exhaust. Should I put the 24 pounders on or leave the 19 pound injectors on?

88 orangepeel notch

If the maf is calibrated to the 24's, definitely. Won't hurt you at all. Your still well below the limit of the 19's, maybe 220 at the wheels. If your maf is still calibrated for the 19's, leave them in. Your safe either way. Good luck.

mjr46

IMO it's still a waste, cause when you actually do some real mods like heads and cam, it'll all have to come back off again.