TBIThrottle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.
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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.
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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.
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.
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.
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.
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.
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.
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.
what kind of an adapter plate are you looking for? One that will mount a larger base 454 onto a standard base intake?
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.
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!!!
