injectors

n\m

19lbs should be enough, but some people will suggest 24's. I guess thats why they say every car is different.

jector 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.

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.

304 HP x .85 = 258 HP
385 HP x .85 = 326 HP
480 HP x .85 = 408 HP
576 HP x .85 = 490 HP
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.

See http://users.erols.com/srweiss/ to get the calculators used in these examples.


If you use larger injectors, you will neeed either a Tweecer, custom dyno tune or an aftermarket MAF calibrated to match the injector size.

An intake, alone, shouldn't be enough to warrant upgrading to 24's. If you had a full H/C/I setup, then yeah, 24's would be a must, but with stock E7's and the stock H.O. cam ... nah. You're safe.

HOWEVER ... since you'll have the fuel rail off, that would be a VERY good time to upgrade to a different KIND of 19# injector. Go nab some newer-design 4-hole injectors from a 4.6L T-Bird or Cougar (orange-ish yellow in color ... some other new Fords use them, as well), put on some new O-rings, and plug them puppies in there. I switched to 'em when my three of my stock injectors cracked and started drooling fuel out the sides, and they haven't given me a problem since. Supposedly, they provide a smoother idle and better combustion because they've got a finer spray pattern - I dunno if there's any reality to that or not, but they are a better quality design, overall.

Even if you don't swap out the injectors for new/different ones, DEFINITELY replace the O-rings and pintle caps while you've got 'em out. You do NOT wanna have to deal with that leaky headache later on, trust me.