Ok im gonna order some injectors for my motor and was thinking about going with 30lb then asked a friend of mine and they said they think that might be 2 much and said i should go with 24 im lookin for this car to be a every day driver so i dont want to have big driveability problems with running to rich or to lean need sugestions plz

 

Here is a good formula to find out what size injectors you need
(H*B) / (C*D)= estimated injector size

H=horsepower (Rear wheel)
B=*B.S.F.C. (see below)***
C=number of cylinders
D=duty cycle (constant .80-.85)

B.S.F.C.=
Low to med. performance = .50
Performance engine with head work= .45
High performance with lots of head work= .40-.45
S/C or T/C engines= .55-.60

Here is an example using my car,
(300*.45) / (8*.80) = 21.09

Guessing that my 8cyl. car with heads is 300rwhp, and at 80% duty cycle would need somewhere around or above 21lb injectors. That is at 80% duty cycle, which is the most that you would want to run on injectors (to be safe), so 24lb. should be good for my application.

You can use this equation to find what duty cycle your current injectors are running. For example: using x = duty cycle
(300*.45) / (8 * X) = 24lb injectors
x= 70.3% duty cycle

***B.S.F.C. = brake specific fuel consumption, it is the number of pounds of fuel it takes to make 1 horsepower for 1 hour. B.S.F.C values vary from engine to engine depending on its efficiency. The more efficient the lower the B.S.F.C. value, which translates into needing less fuel to make 1 horsepower. This changes for forced induction applications due to the engine needing fuel to cool the combustion chamber, which helps prevent detonation.

 

I would use 30lb as a minimum.

 

well i dunno, it all depends on supporting mods, and the tune. a plain 'ol 347 stroker with the most common(from what i've seen) gt-40 heads and a good intake, you'll probably see 350rwhp N/A, and i've heard that 19# injectors will easily do 400rwhp. IMO, 30#'s might be overkill, if your trying to keep it a good DD.

 

A 19lb injector will not make 400rwhp. About 300hp at the flywheel and you should upgrade. 300rwhp on a 19lb injector is pushing them hard. An average, mild 347 should knock down 375rwhp. With a "good" set of heads, a "good" intake and a custom cam, they should be 400+rwhp. I'd expect 420rwhp from an EFI pump gas 347 with the help of Jay Allen or Ed Curtis planning the combo with you.

I will use a 24lb injector up until the 375-400hp flywheel range.

 

my friend is running a 347 stroker and has 24# injectors with a 150 shot... the car runs a consistant 10.40-.50 and low 12s i believe on the motor... he says that he even runs rich some time with the 24# injectors so i think 24# would work just fine for ya

 

if ur not running spray go with 24's i had 30 and it was running rich it n/a form

 

The nitrous will have nothing to do with it if it's a wet kit. So don't worry about that. If it's only running low 12s, then a 24lb injector should be fine because he's not making any power.

If you build a weak 347, then a 24lb injector should do just fine. If you accidently assemble a combo that makes the power a 347 should, a 24lb injector will not support it.

 

yea i think that the 30's would have been for me when i got my heads and then the nitrous

 

At least 30's. I have 30's on mine, but am going up to 42's becuz of the SC.

It won't screw you up with the right tune and 42's would be the way to go if you're looking to do an SC down the road.