Okay i am sure it has been asked before but are the 90lb injectors from a 1991 454CI TBI the same phisical size as the 40lb injectors from my 305 TBI?I would check them but the nearest parts store has to special order them with all the money down.It just seems like a waste of 65$ for one if it does not work!

If anyone can tell me the switch straight up for sure it would be much appreciated!

 

They are a straight switch, but your 305 injectors are 55#, NOT 40#.

 

Okay thank u much Fast355!I am still going to need the 90's either way!I really did not know they were 55#.They 90# will make perfect 200lbs at 60PSI Fuel Pressure!That is as long as the 454's are normally rated at 13-15 PSI like the 55#!If not i still got 200Lbs to go!lol!Thanks alot!

 

Why 200 lbs/hr out of each injector? Are you planning on trying to build 750 HP? I think the upper limit of a 2bbl TBI setup is around 500 FWHP with a bored 454 TBI unit. A 2.3" bore 454 TBI unit will flow about 850 CFM.

 

Well it is a pure project car that is getting a t3/t4 turbo and in all honesty i doubt i will ever hit 750hp!The reason i want 200lb injectors is that i have the capability to hit high horse power and not worry ab running out of injector!I am also thinking the higher the flow capacity the lower the duty cycle has to be!Is my thinking off?

Either way i will be able to turn them down to what works the best with my fuel pressure regulator.

 

Sometimes Bigger is not Better. Oversizing your injectors can cause problems with idle and low end performance. In particular the 454 injectors can cause idle problems when used on smaller engines. The 65# "cop car" injectors might make more sense for you, but it depends on your engine size, HP and RPM range. Do some more reading of the "stickies" in this forum before you blow your dough, all the answers are in here.

Paul T.

 

Okay thanks guys!I have alot of work and reading to do yet!lol!

 

The injectors are not linear either. Just because you run at 60 psi doesn't mean you will get 200 lbs per hour.

 

I thought 454 injectors were 72lbs, also? Or 80lbs? I know they're not 90lbs.

 

my 90's idle great at 14.5 psi.
I forgot the actual part number, but when I bought them I confirmed them to be actual 90# inj's.

 

I believe it was the 454ss that had 90# injectors.

 

I do realize that it is not a for sure thing that i will run 2oolbs all the time but it is probably the max they will ever see at 60PSI!i just need to know that stuff to set up my engine constants for my MS!Oh and as for weather they are 72# or 90# i will double check on All Data and Mitchell on Demand tomarrow morning!If they are 72# they may even work out a bit better for me from one of the earlier posts!At 60PSI the 72# will act as about 155# which should hold 526Hp!Either way i will post what i find on the injectors!

 

Sorry guys i can't put the argument to rest!If it is in Mitchell on Demand or All Data i can't find it.All i found was stock specific fuel pressures for them!

 

91chevz, can you give some more info on your engine size, max HP and RPM range?

Did you find that the 68# injectors didn't supply enough fuel for your engine or did you start right out with the 90# ones?

Thanks,

Paul T.

 

Alrighty then, I learned something today. A little Yahoo search revealed GM has put 72lbs, 80lbs, and 90lbs injectors into 454 TBI engines.

 

The 80 and 90 lb/hr injectors are common. The first of the TBI 454 engines around 1987-1989 had 90# injectors. In an effort to clean up the emissions GM switched down to 80# injectors. Finally in a last ditch effort they put the 72# injectors in. Be careful though with the 72# injectors, they are in reality 46# 4.3 injectors, running at 28-30 psi fuel pressure.

 

Hate to burst your bubble though. The stock TBI wont take much boost without leaking pressure and one T3/T4 will choke the engine out.

On my soon project im going ot use TWO innovative T4e 60's. those are big *** turbos.

for one turbo to be any worth while you'll be lookin at maybe a t76 at minimum or maybe stock dodge diesel holset. Optimal would be a t88 although that's just throwing ideas out not knowing the application or motor specifics

 

When I swapped in my new engine (GMPP 350HO), I knew my stock 350 inj's wouldn't cut it and I didn't want to take my fuel tank out to put in a new high pressure pump so I just bought some 90's and put an AFPR on the t-body. Did the math and the 90's at 14.5 psi can support 359 HP, which leaves some cushion on GM's 330 HP rating for the engine. I'm probably pushing the limits on my stock FP, but it held solid through about 8 dyno runs and I haven't had issues lately. My max duty cycle was I think in the 80's on the dyno, so I'm happy I went with the 90's.
-Passed emissions (I/M 240 dyno), also. no EGR, 2 cats ( 1 for each bank)

here's GMPP's site on the 350HO
http://www.gmperformanceparts.com/En...9711&engCat=sb

I'm using GMPP's vortec TBI intake bored to 50mm, a 50mm CFM-Tech spacer, 50mm xtremeFI t-body (with the 90's).
Mike

 

Okay i have a 357CI Small block all new parts 8.5:1 compression ratio never been dynoed!I swapped a 305 for it.I don't want to run it over 6800 RPM if i can at all help it!I am hoping for about the max on a TBI setup from the sounds of it!Praying i can get 500 HP.The only thing that has varied from stock is i put an RV cam in it!(202 heads bumped the compression up way to high for a turbo!)

The turbo is not a true T3/T4 turbo.Truthfully it came off my uncle's blown up 1991 6.2 turbo diesel!It is a IHI Borg Warner GM1!It is still in great shape.I had heard that this turbo was close to a T3/T4!I had also figured if it can supply a 6.2 with 10 PSI wastegated 5.7 should be a peice of cake!I know most you guys are thinking a diesel turbo is different from a gas!Other than spool rate that is not true.I am really a diesel tech playin with gas!lol! a turbo is a turbo!I would have used a Series 60 turbo but that turbo was just way to big!But i have seen one of those big ones spool up to 140,000 RPM!

I am figuring on hitting 10 PSI by 2000 RPM and holding it all the way through the RPM band!

All i had was the 55# injectors that came stock on the 305 so i have 2 injector comming in today that should be 90#!They come out of a 1991 K3500 P/U 7.4L.If anyone knows for sure these are not 90# please let me know.Either way my Megasquirt will tell me if they are to much and i will either decrease pulse widths or pressure!

Did i answer all the questions?If not sorry.Keep the input commin it helps to see others point of veiw!

Thanks!

 

Mike, thanks for that detailed info on your TBI setup. I'm considering swapping a motor with similar HP into my '91 Caprice wagon, I like the car a lot but I want more power. I'm looking hard at GM's HT383 crate motor, I like it because it has a pretty mild cam and a broad torque curve (this would be a daily driver) but still makes 340 HP. From your experience on the dyno it sounds like the 90's would be necessary on my engine swap also.

I've been looking hard at the same xtremeFI and cfm-tech parts you used, along with the GM Vortec/TBI intake so its good to hear that they worked well for you.

Did you burn your own chip or work with an outside chip company?

What HP did you hit on the chassis dyno?

Thanks,

Paul T.

 

I burned my own chip 260 HP on the dyno. A little low I guess, but I have big wheels and tires, 4x4 gear. I'm sure there are a few more ponies in there somewhere

plus I have a 9.5 inch 14 bolt rear axle and a mechanical fan which will be gone soon

 

Backing out a typical 20% drivetrain loss puts you at 325 HP, and as you mentioned you're probably burning off some HP with the big tires so the engines probably putting out around 340HP or so at the flywheel, not too shabby.

Paul T.