I have searched, but I cannot find an answer to my question. I am trying to find the actual part # for 90 lb injectors. No one seems to know. I found "GM 5235231 *RPD" on Z28Boy's website. But that number doesn't cross reference with any available part #. Now this is where it really gets confusing. I emailed the technical department at turbocity.com with the following letter: On several other 'tech' forums the 2 types of injectors that you sell as Part # 630-121 are listed separately and described differently. The injectors with "black/blue" color codes are listed as 80#/hr injectors. The injectors with "red/blue" color codes are listed as 90#/hr injectors. You list both of these types of injectors as 75#/hr injectors. I am certainly not disputing your info. However, I was interesting in buying a set of the 90#/hr injectors. Can you offer any further explanation and description of the injectors in question? Thank you for your help. Here's their response: Injector rating is subjective with regards to the pressure that they are flowed at. We use the flow ratings of Rochester. The 75# injector would be an 80#-90# flowed at a higher pressure. It is a way to make you think that the injector is bigger. Here's the web page in question: Turbo City - Rock-It Parts Can anyone clear all of this up for me? Are 80 lb & 90 lb injectors really the same? If they are not the same, does anyone have the 90 lb injector part #? If no one has the actual part #, can someone at least tell me exactly which vehicle the 90 lb injectors were used on (I've read totally different answers to this question as well)? Thank you for any and all of your help.

I needed to get home for the injectors numbers before I could post. . .

Years ago I ordered and received the GM# 17111784 injectors (ordered by this part #). These are supposedly the 90#/hr units. They are paint marked at DarkRed/DarkBlue.

And have the laser etched # of 5235231

They are basically an 80.5 #/hr injector. I am running them at 22psi on a hot 327. If they were a 90#/hr injector this engine would be well over 400 HP. Which it isn't.

One very open item is the actual fuel pressure for the flow ratings. The GM service manual states serveice pressure as being 9 to 13 psi. This doesn't help with the actual flow. At these low pressues even a small change in pressure will affect a large change in flow.

RBob.

Ok, about the injectors is true. However, by doing the math which is a constant...An 80 lbhr injector which GM normally rates injectors at 12psi FP. At a 90% duty cycle (which is a bit high, 85% is much better) would in theory support roughly 320HP.

Now, if you increase the FP of the same injector to 22psi and the same duty cycle you could, again in theory support 433HP and you will be flowing slightly over 108.3 lbhr. Duty cycle and regulated FP will determine the flow rate and supported HP. This is of course all based on just two TB injectors.

This may not be what your asking, but as you can see you really don't necessarily need a higher injector to achieve a higher lbhr. just increase FP and do the math.

BTW: A 90 lbhr injector @ 12psi 90%dc with support about 360HP and @ 22psi will support 487HP and be flowing 121.8 lbhr. Do you need that much gas?? Just my .02

Thank you very much!!

Hey Fade...I can send you a spreadsheet that I modified to do all the calculations for any number of injectors, engine, stroke and the BPW value to enter into your ECM etc...to see what the outcome and the supporrted HP will be. It's real handy to have, your choice. Let me know where to send it if you want it.

how about we get that sheet in web format for the site then....

snflupigus...I sent you mail and attached the spreadsheet for the injectors. Enjoy!

http://www.users.bigpond.net.au/ben_...ctorsizing.xls

also calcs you BPW.

thanks to Ben 73. world record holding TBI owner.