brettmc

I need some larger injectors. AI recommends 36# for the h/c package they will brew up for me but after looking at an injector-sizing formula:

Injector Flow Rate (lb/hr) = Engine HP x BSFC /
Number of Injectors x Injector duty cycle

Using 500 hp, .5 bsfc and .8 for the duty cycle I come up with 39. So, with that in mind I'm looking for some 42# injectors.

Now for the schooling. Does brand make any difference? Why do some ppl use Ford injectors? Do I need a certain style/type for the LT1? Will any 42# injector fit the LT1 rail?

Injector fun

Brett

StealthFormula

iTrader: (35)

If your just running a heads/cam setup on a stock bottom end which I am assuming then the 36's will be sufficient. Many even run 30's like I do in a similar setup and along with my Racetronix 255 pump, I have all the fuel I need.

The Ford injectors also refered to as Bosch and SVO's and are popular because they are a very high quality injector. The 30's are the red tops, the 36's are the blue tops and the 42's are the green tops. They have the correct EV1 connectors so they directly fit an LT1 no problem.

With that said the blue top 36's are pretty hard to come by these days. There are other good injector manufacturers such as Racetronix, Delphi etc. that offer 37's and 38's. If you want to go with 42's I would suggest you get the green top Ford's. Running more injector than you need will not be an issue since you can take care of that in the tune. The only downside is that the 42's seem to be more money than the 36's/37's/38's atleast from my research.


Here's what the Ford green top 42#'s look like:


The 30's will be the same just red at the top and the 36's will be blue at the top.

brettmc

Thanks for the info. I got the EV1 connector part but what about the bottom that fits in the fuel rail? Is there some designation as to the style/type of that connection?

illusions

iTrader: (3)

You also want to know at what fuel pressure are the injectors rated at. not all injectors are rated at 43.5 psi some are 60psi. For an example purpose only, if you got a 42lb injector rated at 60psi when you install it in the 43.5psi system your flow rate will be lower than the advertised injector. same is true in the other direction. if you look at a 42 lb injector sized with 39lb fuel system and its installed into a 43.5lb system you will see greater fuel pressure than the advertised amount.

djjab57

iTrader: (17)

L.E. recomended the 36# for my build and better fuel pump but couldnt really find any so i just went with the 37#

ws6t3rror

iTrader: (3)

Brand doesn't make much of a difference but the design/style of injector does. Without having you go through and try to figure out what is good and what isn't, I will just say go for some of the bosch "design 3" style of injectors. They are pretty easy to spot because they are skinny like an ls1 injector. The fast 36lb injectors fit this, or you can get some from fuel injector connection for less money. These injectors produce a very fine droplet size they are also very quick and as a result precise compared to other injectors, also if you find your fuel flow lacking they can be run up to 60psi without having problems (btdt got the shirt).

Also understand that while the formula you posted is correct it is making some VERY safe assumptions. Your bsfc will very likely not be 0.5 most times it will be in the 0.43-0.45 range on a well built engine. 80% duty cycle is again very safe.

Having said all that and tuned a BUNCH of h/c lt1 cars, its quite a bit harder than most people think to max out 36lb injectors. You trust AI to port your heads and select your cam and supporting pieces for you, but you don't think they know what it takes to fuel one of their combos?

brettmc

Thanks for the info man. You raise a good point. While I do trust them on the injectors, I am looking to the future also. This h/c combo is going on a stock rebuild bottom end. At this hp level (and considering my leadfoot), there's really no telling how long it will hold up. Hopefully it will be together for a while but if it does implode, I would like to move the entire topend onto a forged 383 or a 396 and use a power adder, most likely a small hit of nitrous.

Brett

01fxst

I used 42# with my 383 and after tuning they are working fine. Not sure if it is worth it, but I paid a few more dollars and bought matched injectors. I figured it couldn't hurt to have them flow matched closer than the manufacturer will.

James Montigny

iTrader: (13)

I ran SVO 30# on my H/C 350, they did fine but I was really pushing towards the 85% duty cycle.
36# would have been a better choice.
I run 42# Racetronix (Lucas) injectors in my 383, they're more than enough.

Going a little big won't hurt you, going too small will.
Just be sure the tuner knows what brand and size injectors you have.

Flow matched, or not ... it's up to you. I prefer to have mine as close as possible.

brettmc

fuel injector connection has some VERY attractive prices. I also found some 42# green tops for < $250 at an auction site.

1 Craz28

After purchasing Bosch 36#er's I realized that they are 3/16th's too short! O'well they are'nt leaking?

dangalla

i have been told that choosing an injector that is to big for your application will decrease fuel atomization and power. not to mention that a bigger injector is harder to get the idle right

i am running SVO 30's at around 85% duty cycle, i think 36's will be just fine for your application but i wouldnt go any bigger

stevo9389

i got my 42s on buyfordracing.com when they had a sale for $200.

ryanisfast

question for you guys. I'm running a cc503 size cam with stock injectors, but the motor and heads are untouched. Will I be ok with the stock size injectors. Is there more power to be made by switching to bigger injectors or is it more about reliablity and not getting too close to maxing out the smaller injectors?

BTW, I still have yet to get the car tuned. I'm saving up to get it Dyno Tuned.

StealthFormula

iTrader: (35)

I ran the cc503 with stock heads and stock 24# injectors without any issues. I am not aware of where the duty cycle was but most people run the stock injectors with cam-only swaps and have no issues whatsoever. With that setup there is not more power to be had with larger injectors. Best bet is to check out the duty cycle when you get the car dyno tuned and go from there, but injectors are not something I would invest in yet.

1badzee

iTrader: (12)

My old setup was a VERY mild heads/cam (similar to hotcam) on a 355 and I was running 42's with no issues.. It was tuned, idled fine, made pretty decent power and felt good while driving. ::shrug::