Bought a TBI off the classifieds here on TGO last week. In the pictures, it looked like a Marine TBI. Got the TBI in today and it IS a Marine TBI. The first marine TBI that I bought had the Pink/Purple 1994-1995 high pressure injectors in it (75# @ 28 psi, 46# @ 11 psi) and had a 28 psi fuel pressure regulator. Well this 2nd one has the same 2" bores, the 28psi regulator and a pair of injectors that I have never come across. I did some internet searching and have been unable to pin-point their flowrate. I can tell you that the engine they came off of based on the TBI casting. They came off of a Marine 454 making roughly 385 FWHP @ 4,600 rpm. My guess is they are around 100# @ 28 psi, but I cannot gaurentee it. I am looking for more information on these injectors. If anyone has run across them and has information please let me know. T Yellow/Black color code with Rochestor markings 25170301*ACR and 5176 GM The TBI is casting 17096259. The neat thing I found about the spacer is the fact that leading from the TBI pattern to the carb oval pattern are little grooves machined into it. They are rough to the touch and seem like they would help A/F atomization and mixture distribution.

are the throttle body housings the same size as regular throttle bodies? You said it has a 2" bore, I'm wondering if the 454 trucks got the same thing.

Nevermind....I didn't see your pics at first.

Wow Fast...that is quite a find. I am very interested in your findings...

JB

Fast,
I have a sheet somewhere that lists G.M. injector color codes along with their psi ratings and application. I'll see if I can dig it up this weekend and post it for you and others. I'm thinking there 95's but dont quote me on that till I check.

Fast, Sorry No luck. The link I was thinking about didn't list the injectors you were refering to and its probably the same link you checked also.


http://www.diy-efi.org/gmecm/compone...injectors.html

That TBI in the picture looks very simular to the one I just bought! I was amazed when I set it on top of a performer intake and it bolted right up. I'll take a few pics. The spacer on the bottom of mine is a little thicker though...probably almost 2 inches thick. I'm really curious about it's application.

That is an interesting find.I don't know if this link to Turbo City will help but it's an injector chart with flow comparison.
http://www.turbocity.com/default.php?cPath=16_30

I know this is 2 years old, but I just came across this post and thought I'd add to it for future reference.

25170301 injectors are marine injectors and can't be found anymore. I have pulled apart about 6 of these TBI units with these exact injectors in them. I sent them off to be cleaned and flow-tested and they are ~760cc/min @ 14.7psi. This is the exact same flow rate as the 5235206 5.7L TBI injectors when tested at 14.7psi.

Hope this helps.

Does anyone have a part number for that GM adapter plate?

what kind of an adapter plate are you looking for? One that will mount a larger base 454 onto a standard base intake?

I found that out as well. Its just that they are the true high pressure design like the high pressure 4.3 sized injectors in the 94-95 TBI 454 trucks. The 25170301s ran with a 28-32 PSI regulator and flowed substantially more than the ~760cc/min when running at 32 psi.

Yes, you are correct. I tested them at 14.7psi as I do with 90% of my injectors and they flowed 760cc/min. At 30psi they flowed around 1050cc/min.

I have found that the typical "90lb" 5235231 injectors don't do well above 30+ psi. The higher the pressure above that the more they "shut" down or lose their flow. "80lb" 17084304 injectors do much better and have a nice linear increase in pressure up to about 40psi then they lose as well.

Just some info for those who like this kind of stuff. The only reason why i tested at these pressures was because of an old "dude" at ACDelco who I have spoke with a while back and he stated he would test all his TBI injectors at or around 75psi just to prove they could handle it.

I have had a few customers who have needed high pressures to support their setups.

Kind of a fun project.

Obviously, the marine injectors and the 94-95 7.4L injectors are designed for higher pressures.

DC,

Can you test injectors for voltage offsets etc? I want to learn more about getting real world values about injectors.

There is gold in these here revived posts!

I guess the most appropriate response is I'm exploring my options.

I have what I can only assume is a 305 TBI unit. I also have a larger 454 unit I got on ebay that has the 74# @ 28 psi injectors. I want to make about ~300hp. Now the math says that for that amount of power the roughly 500 CFM of the standard TBI should be sufficient. However I doubt it would work with the small plenum of a dual plane manifold, so I want to use a small single plane like a victor jr. That way I can tune the plenum size with spacers to make it perfect for my application.

So guess what I'm looking for is a is a 1-11/16 TBI to square bore adapter plate.

Those plates are easily found on eBay. I am designing a plate now that will adapt the 7.4L TBI units that have been bored to 53-54mm to the single plane/square bore intakes.

Once that is done then i will focus on the adapter for stock SBC TBI units and stock 7.4L units as well.

So for a standard TBI, the bores aren't wider than a standard square bore carb interface? That's good to know.

Not too sure what you mean regarding the bores, etc.

Here is a picture of a typical square bore intake gasket and the stock 5.0L-5.7L TBI gasket.

As you see the bores of the TBI are wider than the intake area of the carb gasket. This requires an adapter that transitions the 44mm TBI bores down to fit within the gasket. This way you don't have fuel dumping onto the ledge of the carb intake. Most adapters don't do the transition and most are not concerned with it, but i am way too particular, lol.

The carb intake is oriented in the wrong position in the picture, but the opening is still the same... Just thought I'd point that out because someone on this board would, lol!!!

ever hear of wall wetting?

that is an example of ledge wetting !

What if you made an adapter that turned the TB 45 degrees like some of the old single plane intakes had carb mounting bosses turned?

im sure they could make it work. but on a 2 yr old thread I doubt thier is a need anymore

Its funny you mention this, those injectors are going to be used again on my Van. Have an Edelbrock Victor Jr 4bbl intake, the square bore Marine adapter, and that TBI unit along with a 7427 PCM and a 4L60E.

The TPI is going onto an E85 burning 12.5:1 Vortec 355 that is going into my brothers 1980 C10 truck to replace the 305.

Sounds sweet man

It has a forged 9:1 383 in the Van if that tells you what I built the motor to run on the track with. The small pill is 75, and the large 125. Will be spraying an additional 200 hp over what I make (450 ish)NA

Have a stock rebuild that I did on a 4L80E in the garage should I need it.

im going to spray mine someday. My pistons are forged too. But I dont wanna do it until the car isnt my daily....cant afford to blow and be out of a car.

You're always up to something cool Fast. What ever happened to the 310 that was in the van?

My brother managed to let it freeze sitting in his C10 when it got down to 15*F this past winter. Good job brother, pushed the core plugs out of the block under the motor mounts. Not sure if the block is trash or not, but was already working on a nice high compression 355 to replace it with. The C10 is not a daily driver, but we intend to set it up to run good 1/8 mile times on N20.

The 310 still runs great, no visible signs of cracking, but I have fear for it when the water jackets get some pressure in them.

This is some of the last videos made of it running.

http://www.youtube.com/watch?v=sWlqAgpEyhc

My brother and I are mainly playing with the Mopar Truck bandwagon lately. 4.7s Dakotas and 5.7 Rams. He has the Dakota, I have the Ram.

http://www.youtube.com/watch?v=H7dYtz2xga8

http://www.youtube.com/watch?v=lxBsOGQsR0s

You can usually remedy the problem by grinding the mounting flange on the intake. Most have enough material to provide a decent radius for the transition. You could so a sideways mount, but that would need the use of a custom bracket for the cables.

Regarding big injectors .....

There was a guy who used to work at the place I had my driveshaft balanced who has/had a rock crawler with a stroked 454 TBI. Apparently, TBI is pretty popular with off roaders.

Anyway, we got to talking, he showed me the rock crawler, and showed me some dyno runs he'd done he week before. I don't remember what they were, but they were impressive. I asked him how he got enough air and fuel for a stroked 454. He was running one of those huge sleeved throttle bodies, and he said he was running Brazilian injectors. In Brazil, everything runs on ethanol, and require much bigger jets/injectors because of it.

I found a Brazilian GM parts site and a couple of Brazilian car forums where TBI was being discussed, but my Portugese is nonexistent.

Yes those injectors do exist. I believe the reason for their existance is to allow the use of high ethanol content fuel. That may be particular to South America back in 1980's early 1990's when TBI systems were used OEM.

and tbi is popular with rock crawlers because at different angles carburetors can be finnicky, where the fuel injection is not, and tbi seems to be pretty simple to them comparable to a carburetor

Except in the 80s they were Carb, it wasn't until the mid 90s that they got TBI and they used it until around 2000, then switched them to MPFI. The really big TBI injectors were on the 4.1 TBI, AKA the old 250 I6, single barrel feeding 6 cylinders~150 hp on alcohol. I have been telling people of their existance for YEARS now. ~125-130 lbs/hr each, they make them to fit the later style HD C60 series pod as well.

Mexico/South American market is a really weird one. They made the 99+ NBS Silverado's with the old 5.7 Vortec under the hood and built a TBI L31 from 96 through 98.

For what they are the 250 TBI I6 is not a bad running engine.

http://www.youtube.com/user/biemmi#p/a/u/1/ytUv4Vn9afM

Yeah, but the problem is finding them.........