Starting to assemble the injection system for a 406 SBC, mild hyd roller cam, ported alum heads and headers.

What is the largest injectors I can use and still have a smooth idle and crisp throttle response?

In a mild 400 you can probably run any injector you want that is compatible with the factory ECM drivers (i.e. anything except ultra exotic low impedance injectors)

I'd run at least 30s, probably bigger in a 400 just because there is no reason not too. Idle and throttle response issues are only caused by people that think you can run an injector without setting the PROM to know what it has. Or if you're running a really big cam such that it doesn't move any air at idle and you hit the minimum pulse width for the injector.

Thanks Ed

Sounds like I can use 36 to 42 lb/hr injectors without too much trouble.

What I'm looking at is injectors in the 58 lb/hr range. This way I wouldn't need to raise the fuel pressure to outrageous levels on smaller injectors to keep up with the engine.

Wondering what these 58 lb/hr injectors would do to my idle quality?

36#injectors are good to about 625 HP with the fuel pressure in the 50s. The 58# ones you will need to make about 740 HP to work good. Just remember that you want to run the most pressure you can without injector lock and thats at 70 plus on most injectors.


Or try this link http://www.mustangworks.com/analyzer.html

Go to the fuel analyzer for more help

Jerry

the largest u will need is 30#'ers. well SVO 30's. im running 26#'s @ 60 psi and i run lean.. 28s would be enough, but since i want to add a nitrous kit or s/c. actually i can run the svo 30's * and run them at 45'ish psi* and that be more then enough now.

*edit* as far as peopel saying u need 36-42, 50 lb injectors.. are u even reprogramming ur computers.. cause 36 lb injectors are overkill on a mild 400.

I'm assuming that he is going to be working on his PROM. You're playing with yourself if you go through an engine swap and are running non-stock injectors and just trying to kludge it all together.

And thats why i said i'd run at least 30s, maybe bigger. Dunno if he's runnig MAF or SD but it doesn't matter. As long as the chip knows what it has a 400 will have no problem idling with those injectors. And there is no such thing as overkill when it comes to injector. The lower your duty cycles are, the better, just as long as your minimum idle pulse width doesn't dip too low.

Ed, you hit the nail on the head. Does anyone know if the minimum idle pulse width will dip too low using 58 lb/hr injectors at fuel pressure of 43 psi?

BTW, this will be a SD and I will being tuning the ECM.

Just out of curiousity, why do you want to run such a big injector on your setup? My vote is for 30# SVO injectors at 45 or so psi...

Cost for the injectors is a big item initially and then the real key is minimum pulse width. Like Ed said, ideally go with the biggest injector you can afford/tune to use.

In my case with the my heads a fairly mild cam and good heads, I am shooting for 450-460 HP, but I want to be able to have at least 500 HP with my 30# SVO injectors.

So...what are you trying to figure out? Getting these big injecotrs used or something?

This will be a boosted engine, about 12 pounds tops. That's how I calculate some 750 hp.

Also, I have a nice set of 58 lbs/hr injectors, but can sell them and buy different if I need to do that.