SLeePer350

As the question states, at what point should one consider 36lb injectors on a N/A 350? Yes this means cam and heads are totally allowed and any other bolt on possible. Just no boostin' or strokin'

I am simply curious because when doing all the formulas based on duty cycle and the brake specific variable, I feel like I am getting numbers that are too high, even though I am using relatively conservative input #s.

I just want to know who is actually running 36's on a like setup, or conversely, who knows for a fact that they are too much? [The only answer I don't want to hear is that getting 36s gives you "room to grow".] I am talking about this specific setup and only this one.

The reason I am asking is because I am in the process of picking an injector for my car and I am totally set on SVO 30s, but am curious as to what a 36 would have to offer if the need is there, thats all.

Jon A

I'm running SVO 30's near 80% with a cam on the stock heads (calculated two different ways). I think I'll be upgrading to 36's when I have the heads done. How much power are you planning to make?

SLeePer350

My plans are always changing, but the goal is anywhere from 370-380 rwhp. Of course I could fall shy of this, but I feel the potential is there. I already have heads and cam, and the project so far is basically Jordan Musser Stage 2 ported intake, CSI water pump, walboro 255, reworking exhaust to a massive true dual setup. Car already has most other bolt ons on top of that.

TenaciousZ

I think you'd be alright with just 30's

kmook

On a previous setup i had, i had 36#'ers and they were at 80% DC with around 400rwhp.

SLeePer350

kmook, were the 36s a perfect fit or a bit too much?

i have been getting a range of answers, saying that 24s are good to 400rwhp, but 30s seem common too, occasionally you run across the 36s...

kmook

You cant really go to big on injectors. It's not like if 36#ers work good for me at xxx rwhp and you have 200rwhp less than me than 36#ers won't work for you. Also go bigger and then you dont have to get new ones when you do future upgrades and make more power.

Also look here:
http://www.rceng.com/technical.htm

1 Nasty Bird

all you give up with a bigger injector is a tiny bit of idle fuel control really. You could run 72 lb injectors theyd run OK at high rpm, but fuel control would get worse as the rpm's dropped. Its all about how long the injector is "open" there is a limit to the minimum time its open. worst case scenario if you need a 30 and you get 36's youd run slightly rich at idle, but you can tune the time theyre open and be fine, just dont go too crazy and get something like 48s. Does any of that make sense? its been a long day at work and im rambling i think lol

hvyss

I agree with 1Nasty Bird It is dependent on the the injector pulse width ( time the injector is on). Example my Impala with ported AFR heads and a Hotcam on stock 24lb injectors had a pulse width of 22. Meaning that (the max being 24) my injectors were wide open all the the time at WOT. Now I have a Comp Cams 230/236 XE with the same heads, on a 350 but went to a SVO 30 lb injector and the pulse width is now 14 at WOT. So to me unless you are going to use a large shot of NOS(over 150 shot and not a stock rotating assembly) and a large cam the 30lb SVO's are more than enough to serfice your needs. I hope this helps.
HVY SS

BPS

30 vs 36
both will work fine - get the set that's cheapest.

I'm running 36 but only because I use to have a small blower on the car.

But there are no gain and the computer will adjust - as Nastybird said - there may be an issue with low RPM fuel control with much larger injectors but not between 30 and 36.

you will have to program your PCM and input the new injector size and basic pw data

Jon A

OK, I think 30's would get the job done then. I guess my situation is different--on a cool day I'm already in the 360-370 range so I'll be looking for a lot more when I have the heads done. Enough more that I don't think 30's would be optimum.

SLeePer350

I think I am just going to go with some 30s then...I figured since they are SVO I'll end up getting closer to 32lbs out them anyway going from the Ford to GM fuel pressure. So I should be more than covered.

Is there anything else to look for as far as maintenence or performance tuning besides resetting the pcm to accomodate the bigger squirters? (especially because the injectors will most likely be a used set to save a few bucks) I am assuming that the installation is just plug-n-play once the fuel rail is off?

thanks

johnny o

You don't 'reset' the pcm you will need to reprogram it. I am guessing that you know this but just saying it in case you don't.

TenaciousZ

since they are used injectors, check the 0-rings, I re-installed mine after the head swap and one of them tore. I didn't notice ti'll I was driving it for a day or two.

SLeePer350

woops you got my type-o, yeah i definitely meant reprogram....this will be the second time bryan herter at pcmforless.com will be tuning the car...he does great work and i am sure he care take of a simple injector swap.

another quick question - should i expect to be ok running the stock pump with 30s?? i have a walboro255 sitting at my house, but i dont know when i will get around to putting it in. should i absolutely have this pump in before i do the injectors or doesnt it matter too much, at least short term??

thanks, sorry for the dumb questions...