Hi, I'm putting together a 415-427 ls3 engine. Heads will be cnc'd with a FAST102 intake and tbi. Cam will be a custom grind. Compression will be right at 11 to 1.

My goal is to put 450-500hp to the rear wheels. I've been looking at injector sizing. It seems like 42-50 lb. injectors would fill my needs. My question is, I see injectors for sale here all the time, but are larger; like 60 and 80 lb. pieces.

Would it be OK to put these in my engine, or would I be better off sticking with what the injector calculators say I need? Thanks for any input.

 

yea the injector size has no bearing on the engines performance, unless they are too small and lean the afr out...you can run 80 lb injectors in a stock car, they would just have a super sort pulse width...as long as the duty cycle on your injector is like under 90% your injectors are big enough...usually injectors that big are for FI cars

 

Thanks. I need to get schooled on injectors.

I've seen high impedence, low impedence. Duty cycles. What should I be looking for to get the most out of my injectors. Engine will stay naturally aspiriated and I will use a FAST intake/tbi. No carb or me this time.

 

Your car needs high impedence injectors. Low impedance injectors are for a different style of computer running the engine. There are convertor boxes available to run them on these cars...but with some of the newer larger high impedance injectors out there, it's almost never necessary to switch anymore.

I personally don't like to run much larger than I have to...it's better than too small, but I don't bother.

 

those 42-50you were talking about would be plenty, but if you find 60s cheaper id get them just because...what kind of power are you trying to make? aftermarket heads and exhaust?

 

i just read your previous post and saw cnc heads..what do you mean by tbi? you mean sfi right? because fast intake is an sfi manifold...anyway i think 50 would be perfect for you...but 60 leaves room for more fuel if power goes up through bolt ons and cam

 

tbi was for throttle body. Like a FAST 102 cable-driven unit. And thanks for the input. So I'm going to be looking for high impedence injectors. And I'll shoot for around 50 lb. +/-.

I just know that with a carb setup, you can actually hurt performance by putting too big a carb on an engine. Didn't want to make this mistake with injector size.