I'm about to have some programming done and because I have some 30 lb injectors I can put in, figure now would be best time to install them. I'm just wondering if the stock injectors might be a little overstressed or would the new injectors be a better compliment for my package.

 

stock injectors will be fine, especially if you raise the fuel pressure over stock some. 30lbs will work just fine too as long as you program accordingly

 

I would go with 30's just for some insurance. Dont want to get that duty cycle too high and have problems.

 

Does anyone know what the max horsepower rating is for the stock injectors?

 

Fred says 400-425 crank HP. Mostly depends on your duty cycle. For the price of them, as cheap as 150 used they are a good idea. Many online calculators are available, and Dave based on your trap speed I can tell you you need/could maybe even pick up some HP with bigger injectors.

A friend of mine picked up 15 rwhp going to 30lbs from stockers, he was in the 360 rwhp range.

 

i used 24# injectors on my old setup (cc305, stock heads/bottom end, shorties, and bolt-ons). they were maxed out at 103% of their duty cycle above 6000 rpm's.

i'm using 36# injectors on my new setup (ported stock heads, aggressive hyd. roller, LT's, etc.). they are using 76-78% of their duty cycle at 6800 rpm's.

i considered going with 30's on this new combo, but went with 36's to be safe. i asked a few people and the consensus seemed to be that 36's would be fine with good tuning.

 

Thanks for the replies. I figured the injectors may have been on the borderline so I figured an upgrade was probably necessary.

 

You dont need it, unless your pulse(Duty) cycle go above 98%.

 

huh? i'd be concerned if duty cycles were above 85%.

 

What are the stock injector sizes, something like 24lb right?

With that said, if it's true, then stock injectors are good for about 307.2hp at the crank.

How to determine the correct injector size for your setup, formula:

If you don't know what kinda' power you will be making use this formula to find out what the injectors that you are considering are good for:

((Injector size) x 8 x .8) / .5 = (Crank horse power the injectors are good for)

If you know what kinda' power you will be making use this formula to find the optimal injector size:

((Crank horse power) x .5) / 6.4(which is the same as 8 / .8) = Injector size required

 

Good post.
I have been using 24 lb SVO injectors since my rebuild. I though I had been getting valve float above 6000 rpm, but that might have been my injectors being over stressed now that you bring this up. I may have to invest in some 30 lb injectors now and just get the PCM prgrammed accordingly. Anyone else have 24 lb injectors with Hot Cam and LT4 heads have my problems?

 

I had the same problem I was running a cammed headed high compression motor on the stock 93 injectors and getting what I thought was valve float above say 6, I switched springs to no avail. i then went to a bigger pump and 32 #er and it magicly went away..lol

 

Hmmm....what were the torque numbers on the pulls with what looked like valve float issues? I have a dip at about 5600 that didn't go away with new springs :

http://afrashteh.com/dyno4.jpg

If I remember correctly, you have a 383. I have 30 lb injectors now (was absolutely necessary as the 24s were tapped at 4500). What pump did you go with?

-Alex

 

Dang, I think we are on to something here. For me it happens around 6,000 rpm. Sometimes it does not sputter, but most of the time it does. It's so bad that I set my shift light to 5800 and I should be able to shift at 6200, but I can never make it that high. Come spring, the 24 lb. injectors are gone

 

I'll agree with what other said. For most of our setups, 24lb/hr just wont supply enough fuel.. unless youre running a tiny tiny cam.

Run the 30's for sure.. can only help