just wondering what cams people are running and what injectors you are using. im debating upgrading them, ive heard from a few people that ill need to do it and from most that i wont. ill be running a 230/242 114 LSA 544/576 with 1.6 rr's nitrous cam. my buddy with an 96 impala SS ended up running lean with just a hotcam so im a little worried. just curious to see how everyone else is doing fuel wise.
thanks
brian

 

From what I've read and heard you should be fine. What size injectors does the Impala have? Maybe they are smaller. Still odd it would run lean with just the Hot Cam.

 

thats what im hearing, i know when i spray a 150 wet shot ill need a bigger fuel pump. other than that im hoping ill be ok.
brian

 

The stock 24lb. injectors are sufficient to 450 HP. That's the absolute max. So unless your pushing 450 HP, you should be fine.

 

im hoping for 350rwhp NA and who knows how much with the wet shot. looks like when i run that ill need the 30# injectors.
thanks for your help rich.
brian

 

With the GM 847 cam I use 30lb injectors. my car made a little over 400rwhp so I don't think the stock injectors would have been sufficient.

 

No problem. Glad I could help.

 

grease-what are the specs on the 847 cam? rich-you meant 450 crank HP, right? and what electric cutout are you running?
thanks
brian

 

Flywheel. If there is any doubt in your mind that you are cutting it close go with the 30 lb. injectors. Especially if your going to be spraying. If not you'll wish you had. I'm sure you already know that.

I'm running the QTEC electric cut out.

 

234/242 @ .050, .539/.558 lift with 1.5 rockers, 112 ls. keep in mind I also have ported heads, but even with stock heads and the GM847 cam, I would have gone with 30lb injectors.

My previous setup was a ZZ-409 cam (226/226, .520/.520 lift) with stock heads and I used the stock injectors there.

 

What amount of HP are the 30#s rated to?

 

550hp maybe. i looked in jegs and the holley 36# injectors are rated at 650hp. so somewhere in between 450-650 id say, lol. probably since its smack dab in the middle of 450 and 650 they probably are good to 550 (30 is the average of 24 and 36).
brian

 

Im hoping to make 525HP with my stroker N/A and 750HP on the NOS. I am running 42 lb injectors.

Personally I would not trust the stock injectors to handle 450 HP.
The stockers dont like runnign at much more than 80% duty cycle....they tend to lock up

 

dido TriPinTaz. My feelings exactly!!

 

It seems that all of these "what injector size do I need" threads forget to mention one significant thing: RPM.

An injector that can support 400RWHP at 6000RPM may not be big enough for a car that makes 4000RWHP at 7000RPM. Same amount of HP, but different injector needs.

Why is this you ask?? It's all in the duty cycle. In my above example at 6000RPM, the injector has more time to stay open to dump x amount of fuel. At 7000 RPM, it has less time to dump what would most likely to be the same amount of fuel. So it needs an injector that can dump more fuel when open because it has a shorter time to open.

Hell, a stock 24# injector could probably feed a 800HP supercharged monster if it were to only be driving around town and never above 2000RPM. It's all relative.

Then, we get into fuel pressure. Higher fuel pressure = more fuel flowed at the same duty cycle.

Click here for a fuel injector calculator. Honestly, that calculator seems to be a bit on the conservative side, but should get you in the ballpark.

With my car running pig rich (which of course ups the duty cycles), on stock 24# injectors, I had them maxed out at 5800 RPM. Of course if I wasn't dumping so much fuel, they would haven't maxed out until probably 6200-6400. Regardless, they were too small for my setup (which include ported heads of course), and therefore I went with 30# SVO's.