I've been trying to get some flow numbers from the builder of my motor. He built a 383 with Vortec heads and Vortec TBI intake, and had a third party build the TBI unit. Distance is the main reason for the difficulty of information exchange along with the fact that he seems to be away from the phone all the time. When I picked up the TBI unit, the best answer I could get was that "It flows right at 700cfm."

For the sake of tuning, I decided to take the injectors to be flow tested. They are a pair of 5235206*ACR as stamped on the top of the injectors, my best guess is 61 lb/hr. When I picked them up, the data sheet has a flow rate of 104 as tested at 20psi, I imagine that is a lb/hr number. How does that convert to the 13psi my fuel pressure regulator is set to? Where can I find how to convert the numbers?

 

I may be wrong but I'm pretty sure the following is correct:

The stock flow rating of the injectors is calculated using the stock psi of these car which is about 13psi as you said.

With the stock 61lbs/hr injectors you will get these numbers at 85% duty cycle:

13psi: 61lbs/hr per injector (Will support up to: 230hp)
20psi: 75lbs/hr per injector (Will support up to: 286hp)
24psi: 82lbs/hr per injector (Will support up to: 313hp)

After that, I would recommend bigger injectors.

I have a 355 with stock 81lbs/hr injectors (came off a 454tbi). I have my regulator at 18psi which will support 360hp.


If you need an exact calculation let me know or see if you can ask Bobr for a
calculator or Check this out:

I would like to send you my calculator but its not mine. (©)

http://www.dynamicefi.com/TBI_Fueling.php

 

All this is assuming you got a 2 injector setup.

 

Nice posts napster. I didnt know Rbob had those on his site. Well it looks like i'll be hunting for an AFPR because I have to run over 18 just to get my car to run semi right. Well im ordering the EBL so i'll do that see how well I can get it and then go from there.

 

Ya, Bobr has tons of info on his site and the EBL is the coolest thing ever invented lol

Also I would check this out:

http://www.tbichips.com/truckmods.htm (This will help both of you guys)

 

Yeah Ive read through that before. I have the holley tbi on it now. I wonder how I can verify if it really has 65 pph injectors like Brian say's.

 

I'm no professional about this but the 65lbs/hr is calculated according to the stock pressure (13-15psi)

If you run the "61lbs/hr" injectors at 15psi you will get those injectors to be 65lbs/hr

Or wait, you may be referring to the cop car injectors? Not sure if they are completely different injectors...

But anyways,
FOR example:

I have "81lbs/hr" injectors. When I run them at 18psi, my injectors now magically turned into 95lbs/hr injectors.

If I ran my injectors at the stock 13psi, then I have 81lbs/hr injectors just like I'm supposed to lol

lol not magically but you get what I mean.

 

I just wanna know if the holley tbi has 65pph injectors, im still in the tuning stages so I wanna know about how many lbs im actually running them out. I wonder if I can identify them by a number or something. I'll look into it.

 

Ah, I see. Well I did a quick search and found some info you may find useful. You probably already seen this stuff by just in case you havnt Ill sent it to you.

I'll PM you since I dont want to steal this thread.

 

Just noticed I never really answered your question... the 61lbs/hr injectors at 13 psi will not be enough for your 383 unless you have a 4injector setup.

I dont even think that 20 psi will be enough if you wanted to get the most out of your 383.

I would go with a 454TBI with the 81lb/hr injectors like my setup.

I've been looking into the 4 injector setups and they are really cool.

 

I don't know if these are stock injectors anymore, although they have a stock part number stamped on them. The engine builder had someone else do the TBI unit and says it flows right at 700 cfm (not sure how true that is though). 20psi was used to test the injectors and the flow rate was 104, unit of measure I don't know, but I would like to assume lb/hr. I suppose I'll have to call the shop that tested them and find out so I can convert the number for 13psi. I found a number of conversion calculators, including bobr's (I have EBL Flash too), and if 104 is lb/hr, all will convert to about 84 lb/hr @ 13psi.

Thanks for the info

 

Thats funny, I didnt think you could actually modify the injectors and change the actual physical flow rate of the injectors...

But if you have that injector flowing at 104 with 20psi then that would come out to be a 84lb/hr injector at 13psi... which is something I have never heard of.

Tried looking up an 84lb/hr tbi injector and wasnt able to come up with much.

Maybe they are 81lb/hr but then again they have a stamping of the 61 injector ? That sounds really weird... I would look into that. Hope they didnt give you #61 injectors.

 

I'm going to assume these are stock 5.7L 61lb/hr injectors. 104 is the flow in cc/cycle was what I got over the phone from the shop that flowed them. I couldn't get what the cycle was though.

I'll use these until I can get something a little larger that will fit the injector pod from a stock SBC TBI unit.

 

I thought so... I even had thought about looking for a calculator on Google and start converting 104 too and see if it matched up with 61 lbs/hr with another unit of measurement but I got lazy lol

Your going to have to up the pressure quite a bit to get it going ok and well in order to do that you may need to install a higher pressure regulator inside your TBI unit. Or you can just do what I did any install a block off plate inside the TBI and run an external AFPR on the return line and adjust the pressure as needed.

You might also need to install a higher flow fuel pump.

 

Yup. Variable regulator and new fuel pump are in my plans also. I need to replace the tank due to a leaking filler neck, the sealing surface is all munged up. I have a friend locally who has a tank waiting, and we'll swap at his place and install the pump at the same time.

While I'm looking for injectors, will a set from a BBC TBI fit the pod of an SBC TBI? I see all kinds of 454 injectors on e-Bay, but they're pretty vague on what they'll fit, not that I want to buy any there. Most are 90lb/hr @ 23psi which comes out to be only 67lb/hr @ 13psi.

 

Mmmm no I dont think thats correct. The 454 TBI injectors are true 81lb/hr injectors at 13 psi.

The 90lb/hr injectors are a bit more rare than the#80's.

But the pressure for these cars and trucks running TBI is 13-15psi stock.

Please read this:

http://www.tbichips.com/truckmods.htm

I promise if you take the time to read that it will answer almost all of your questions thanks to Brian.

I'm pretty sure the BBC TBI injectors (80/90's lbers) would fit the SBC pod but I dont think I would recommend it because I think that they spray wider due to the wider 2" bores on the 454 TBI.

I've hear the injectors dont really mess up to easily so you may be able to just buy a junk yard pair or ebay pair and send them out to get pressure tested and cleaned, if you dont have a local place to clean them out,

Go here:

www.injectors4u.com

 

I should have put that in quotation marks as to the flow at test pressure. I take a lot of e-Bay comments with a grain of salt.

I've been to both of those sites and found a lot of good info. I think I found a set of 80# injectors that may work when browsing through all the part numbers on Motor Man's site. I looked at the part numbers and the TBI system they're for and found my 5235206 injectors go to a TBI-220 system (doesn't mean much to me), and so does the 80# 17084304 454 injector. I'll give him a call and see what he can do for me...

 

Man im thinking about buying some 80pph injectors i found on ebay near me...new and flowtested. hmmm. I see mine are 65pph at 13 psi, im running 20something psi now.

 

I'm pretty sure that the ones I have are the 17084304 injectors.

If you guys need any 61# lbers just let me know I have tons of em lol Although they are pretty worthless for the engines we are building/running.

Well what are you trying to get going, UnderCover89TBI ?!

I'm pretty new to all of this too, I probably just started my project a bit earlier than you guys so I can hopefully help you guys out with all of the questions I had when I was getting my car setup going. By helping out others I'm learning as well.

 

Ya, If you ran the 80's you would be able to set your pressure at 13psi and you will have the same flow rate that you do now running your 65's at 20psi. You will need to do a few changes to your bin and you'll be set.

Your current setup will support 300hp so depending on the rest of your setup and engine you could up the pressure on the 80's and you should be able to get some more power out of it.

I notice everyone likes to run lower pressures and still have the same flow out of the injectors, I really dont know why but the sound of lower pressure with equal results does sound like a good thing.

Theres some benefits to lower pressures but in regards to drive ability if it works and runs good and you dont need more flow then you should be ok.

I got all excited when I found the thread in regards to the 140lb injectors until I read though it and the results crushed my thoughts on the idea. lol

https://www.thirdgen.org/forums/tbi/...jectors-2.html

 

lower fuel pressure and same flow equates to less of that rich smell at an idle. I dont even have EBL yet. That is getting ordered in the next few days so im running on a stock tune well i got a hypercrap chip in her. im not trying to get her going im just trying to get her right. I drive mine every day