all the boltons. thanks

 

Depends on compression, and whether or not you are going to spray the car. I would recommend going with some 30 lb injectors if you do not plan on spraying.

 

There are too many variables to just pick an injector size by only knowing that it's a 396 with bolt ons. What kind of power are you expecting? Is it naturally aspirated? Give us a little more info on it.

 

lt4 heads ported from TEA,small solid roller,11.5 comp,58 tb. if i spray it will be a wet kit 150 shot.

 

im building a 396 too but i was gonna go with 36#inj. im gonna spray also but wet. if there a little to big cant you just program them down? id hate to see 94guy or myself buy some that were too small.

 

There are some calculators out there that will tell you what you need based on your expected HP output, NA, SC, N20. Interestingly one I found figured out that I needed 36lbers for my NA 383...I always thought that 30's would be enough...

 

When installing new injectors, the PCM gets reprogrammed so it knows what size they are and can operate them correctly.

But I was wondering this too ... is there any harm in choosing injectors with a little "head room"? Like ue 36# injectors when you only need 30# right now, but plan for the future.

 

I would say 36# injectors just so you have some room to work with. I'd say 30# SVOs would be alright, but like droptop said, you can always tune it to make up for injectors being a little big. If they're too small, there isn't much you can do.

 

I jsut ordered my 383 Nu-tek motor, I will be spraying it. I picked 30lbs SVO's and they will be fine. YOU WILL NEED PCM RE-TUNING. Due to the injector. SVO's are known to flow more than rating. Like 30 is like 32.5. I mean 30 is prob fine, even with the 150 shot, tuning will determine how much of a duty cycle, i mean 100 is bad, 80-90 is good but your nearing the max.

Too small is stock 24lbs so 30 you should be fine, 36 for safe measure.

 

"383=30lbs 396=36lbs" is definately not a good way of choosing what size of injectors to go with. You cannot make a displacement vs. injector size chart and be very accurate. You could take a stock shortblock with a great heads/cam combo and it could need the same size injectors(or bigger) as a 396 with a home port/shelf cam setup. SVOs flow more than their rating because they are rated at 36psi and our cars have 39psi stock. Also, as far as the 150 shot, 94 guy said he would be have a wet kit. When running a wet kit, fuel is added by the nitrous kit not the injectors. So, this wouldn't change the size of injectors needed. Not bashing, just trying to clear some things up.

 

I'm running MSD 55 lb./hr. injectors on my solid roller 396, but it's a little more extreme than "just bolt-ons".

According to the calculator below, with a maximum 675 horsepower, 0.5 BSFC and maximum of 80% injector duty cycle, 42.73 lb./hr. injectors are recommended. I have a little headroom, and the injectors won't have to work that hard most of the time.

http://www.smokemup.com/auto_math/fuel_injector.php

Of course one trick to get more fuel out of an injector at a given duty cycle is to raise fuel pressure, so you can "get away" with smaller injectors if you can raise the fuel line pressure adequately, assuming that you don't exceed about 82-85% duty cycle. At that point, it's probably time to start thinking about larger injectors.

 

Actually, the SVO's are rated at 39 psi, and the LT1's factory fuel pressure is 43.5 psi. This is why when you run the SVO injector at a higher fuel pressure, it flows more than it's rated at.

JR

 

I don't know where I got those numbers. Too little sleep I guess...

 

If you are going with a wet kit, injector size is not relavent. I'd say go 36 or 42 lb injectors because you'll probably be in the 420-440rwhp range. Of course, RPM makes a big difference - the higher you go, the more injector you need (due to duty cycle). The smaller you can get away with, the better IMO.

-Alex