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Limiting HP for 87-91 fuel injetion

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wrathORC, Oct 19, 2002.

  1. wrathORC

    wrathORC 1/2 ton status

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    What is the limiting factor for horsepower on a 87-91 fool-injection system? Searches have proven rather fruitless and I know you guys are a plethora of information. I've been told that due to the design of the system only certain cams work well with it. I want no less than 200hp out of it. If I can squeeze 240 ponies out of a carbureted 305 I should be able to do it with a fool-injected one. I don't like gutless wonders.

    I've found a ragged-out 87 K5 and if I could pick it up for a few hundred I might get it. We're talking inner wheelwells rusted to the point where they don't look like they were ever there to begin with. This Blazer would become my off-road only vehicle, complete with sawzalled fenders, no doors, and bobbed backside. The whole point of this thing is to have something I don't mind if I add new "body lines" to. And after experiencing issues with long wheelbase trucks and inclines that make quadrajets complain what better solution than a butchered K5 that's got injectors?


    Thank you for your time,
    Brian
     
  2. TXsizeK5

    TXsizeK5 1/2 ton status

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    I read about this in peterson's once, how TBI engines are lacking in HP... but dont 350's come with 210HP already? Then headers would give it a little more umph. You can always throw on vortech heads. I would also like to know what cams work good with TBI engines? Thanks
     
  3. mattyblazer

    mattyblazer 1/2 ton status

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    I had a 350 with a carb in my 81' suburban, rusty old box screamed, I mean the truck was noticably fast. When I put her to rest I pulled the 305 out of my 87' blazer (dog), I replaced the 305 with the suburbans 350 and the tbi setup slowed it way down.
    I have the same size gears that the suburban had in the blazer, I put a gibson high flow cat back system on the truck with a high flow converter, a little better.
    Now I am in the process of putting an edelbrock header system that goes to the cat, with a jet stage 2 computer chip, some things gotta work.
    So at least for me the tbi system seems to limit the performance.
    I will post later today when the work is done and tell every one if it helped.

    Matt
     
  4. Derf00

    Derf00 1/2 ton status

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    Depending upon how far you want to go with the mods, the TBI and the computer are the limiting factors. The Third Gen web-site http://www.thirdgen.org/techbb2/forumdisplay.php?s=&forumid=17 is a great source of info. It is the general concensus of opinion on that web-site that over the counter chips are a waste of money and the only proper way to do it is with a custom chip for your vehicle. There are numerous other mods that will greatly enhance the performance of your 350, intake, cam, headers, and Vortec heads are the most common.
     
  5. bigblock454

    bigblock454 Clack Clack Clack Premium Member

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    I used to have a 90 Chevy 1/2 ton with a .060 over 350, CompUCams2030, headers, chip, roller rockers and raised fuel pressure. It ran great, it would burn both back tires (275 60s) with 3.43 rear gear 1/2 way through 2nd gear. I ended up breaking the crankshaft, sold it cheap and bought my K5.
     
  6. BigOrange90Jimmy

    BigOrange90Jimmy 1/2 ton status Premium Member

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    ditch the factory manifolds, or get the HD 350 manifolds (can't remember the years or trucks) or put on some headers, free(er) flowing exhaust, REBUILD THE THROTTLE BODY!!!! (it helps, trust me), ditch the smog pump if it's got one and if you can get away with it, change 02 sensor, K&N filter(s), some sort of cold air intake, and some other little odds and ends should help a bunch
     
  7. blazen_md

    blazen_md 1/2 ton status

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    Here is what I have done. K&N filter, poweraid throttle body spacer, flowmaster exhaust, and I have an accel super coil, 9mm wires, and bosch platinum +4 plugs. I know this isn't a whole lot but it doesn't run too bad. I heard the biggest cam that you could put in a tbi 350 is something
    with like a 220 or so duration, I am not sure about the duration I think it is around 220 but it is around the size of the one that comes in the ram jet 350. (this is all in a 90k5 with a 350tbi)
     
  8. imiceman44

    imiceman44 1 ton status

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    TBI praise.
    If you have the time, read this and you can see that TBI could be better than Carb or TPI for what we use the engine for.
    I know I had an 89 TBI350 and it was good, much better than my 79 350 4bbl.
     
  9. BigOrange90Jimmy

    BigOrange90Jimmy 1/2 ton status Premium Member

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    Just adding more info. This is coming from the Dec. 2001 issue of Petersen's. They say about the most you can expect from TBI is 360 hp. Supplying them with enough fuel and keeping them emissions legal are the huge limitations. A stock TBI 350 makes 210 hp @ 4000 rpm and 300 lb-ft of torque @ 2500 rpm. That's with the stock 9.3:1 compression ratio. Edelbrock, Crane, Comp, and Lunati all make cams for TBI. These range from 194/214 to 205/215.
     
  10. HarryH3

    HarryH3 1 ton status Author

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    The TBI setup on a factory 350 was designed to supply enough fuel for a 210 HP engine. Bolting it to an engine that is capable of more power gets complex. You can tweak the fuel pressure, install larger injectors and play with the computer programming to get it to feed a higher output engine. But at some point you run into the airflow limit of the throttle body. It can only flow a certain amount of air. So then you step up to a larger throttle body that will flow more air. And oh yeah, go back and reprogram the computer again. /forums/images/graemlins/wink.gif

    Holley makes off-the-shelf fuel injection systems that will run an engine up to 550 HP. There are some other companies out there (such as DFI) that will build a fuel injection system for any horsepower level that you can dream up. There is no limit to how much power EFI can make, it's just a question of how much you want to spend. The reason that you don't (yet) see EFI at the track is that the sanctioning bodies have rules against it, except in the street racer classes.
     

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