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Thread: need some input

  1. #1
    Electronic Ignition!
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    need some input

    Kicking around changing directions in my project truck, and I'm kind of at a loss as to which parts would be best suited for my application.

    I'm looking to modify a stock 94 TBI harness to basically a standalone harness, I'd like to also retain the stock instrumentation for the truck while installing this harness.

    Truck is an 84 C10 body, on a 4x4 chassis.
    Engine is a L31 Vortec replacement crate engine, completely stock with an Edelbrock Performer RPM (noon Air Gap).
    Trans is a 94 4L80e with an NP241 behind it with a cable drive speedometer.

    Here's where I come into my question of what the best route to proceed is... I've accumulated some TBI parts...

    A complete 94 454 TBI setup, originally on the 454 that was in front of my 80e. This is the high pressure, small injectors setup.
    Or
    Complete 94 2wd 350/60e setup. (I'm told this requires moving 2 wires in the harness to work with the 80e, and only used one VSS, as opposed to one in the trans and one on the output housing if the transfer case-making use of my cable driven speedo easy, plus it's already sized to fit my small block!)

    Is one of these harnesses going to be easier to modify to work with my application, or just be overall "better" to work with? Both run on a 7427 PCM, which isn't an issue as the truck the engine is currently in has a modified 7427 in it that I can use.

  2. #2
    Electronic Ignition!
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    Should probably also add that I have a 350 TBI, ridges removed-stock bore, injector spacer, AFPR, currently on the engine.

    The truck will be used as an occasional driver and work truck, as well as carrying a plow.

  3. #3
    Fuel Injected!
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    My opinion in your case. I did the same conversion in my old 77 crew cab but used an AZ SPD and Marine intake with ECM and TCM.
    Do you have twin tanks or single? I ran a set up in my open non tub tank and the pump burned up. It was a New Delco pump and it never ran lower than 1/2. Truck use was highway and once in a while city. Pump had 2,000 miles before failure. Low then later no pressure. (And I was warned of this @ Work from the Delco boys even...Duh The tanks in Michigan were so rusted it wasn't worht any time or $ on them. In TN that is not the case here.)

    My point is this: My set up used the right tank as main and left as reserve to pump into right. I used a GM 89 F-car sending unit with GM pump in my 77 tank. No TUB as yours does. I wouldn't do this again, use a main and then pump gas from one tank into the other even with a manual switch. I use a canister on both tanks.

    You should decide if you want to retain the twin tanks or single.

    I would begin searching for a 1987 TBI Truck tank or tanks. If you want twin side saddle tanks and a switching valve, you will need the dash tank switch w/pigtail, tank sw valve under cab, tanks with tubs, sending units and new pumps with socks. I bought a Spectra sending unit and had to throw away ALL the wiring, connectors, and inside splices that were China/India junk and very weak connectors. Spend the funds and get the good ones, the cheap will fail leaving you on the side of the road. The tubs are critical. Use Gates barrier EFI hose for this ethanol added fuel that eats rubber hose.
    I found in TN the used tanks were only 20-40 less than new aftermarket tanks. If you get used tanks, GET from the Filler neck,gas cap, and all the hoses to the tank. I needed the hoses as my filler size was smaller/larger from 77 filler to 87 tank. The vent hose was the same size. The Gates filler hose was 30.

    If you have an 4L80-E and use a GM PCM, follow this. For 1991-1993 4L80-E units, use a 91-93 PCM. For 94 up use a 94 up PCM up. There is a difference and if you swap the wrong combo the trans can fail from low and or hi pressures. Trans cooler lines. Don't use any rubber hose even the SS Rubber. It fails. Use steel and or Teflon lined SS hose. Parker is cheaper than other brands, if you get a corp discount.
    The wiring is your pick because you have to do the modifications to what you want. I found the tank/lines the biggest wall to climb.

  4. #4
    Electronic Ignition!
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    I actually harvested the entire drivetrain and harness from a 94 K3500 at one point. Sold off the longblock, and the transfer case (driver's side differential while my GM straight axles are passenger side differential -of no use to me.) So I have the entire 454 injection setup, and the trans it left the factory with.

    As for the tank issue, I've got an 87 tank I set back specifically for this purpose, though I was going to do a 350/TH400 swap in my 77, using 87 parts. That project is a ways down the road, and I may just keep it carbureted at this point.

    I guess my biggest question is, is the 454 TBI system overkill for my engine?

    I do like your idea of using one tank as a reserve, rather than using a troublesome switch. It would sure make plumbing a lot easier.

  5. #5
    Fuel Injected!
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    No, the 454 throttle body should work great on the Vortec motor after some tuning. Just make sure your throttle body adapter is sized for the bigger bores.
    1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
    1975 280Z, TBI 350, 700R4
    1953 M-38A1, TBI Buick 231
    1951 Ford Panel, 5.3 with 4L80E

  6. #6
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    Quote Originally Posted by fastacton View Post
    No, the 454 throttle body should work great on the Vortec motor after some tuning. Just make sure your throttle body adapter is sized for the bigger bores.
    I don't think my existing adapter has big enough bores. It is a .25" steel plate, and I've had sealing issues with it a couple times. Perhaps going to a thicker aluminum version would be a good upgrade anyways. Who doesn't like more plenum volume? As for the tune, where do you guys think I should start, since this thing is going to be totally different than my existing setup. I've heard just to take the Vortec timing tables and tune the fuel from there using the stock BIN. Should I use a 350 BIN, or start with the 454?

  7. #7
    Fuel Injected! jim_in_dorris's Avatar
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    Grease, If I was using a 454 TB, I would use the adapter that GM used. All 454 TBI's were mounted to 4 bbl carb intakes. Attachment 8942Attachment 8943

    I would use the 350 bin, what ECM are you using?
    Square body stepsides forever!!!

  8. #8
    Fuel Injected! sturgillbd's Avatar
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    The 1991 454 didn't use an adapter. I apologize for the out of focus pics but here is what the later 454 intake looks like. I also have one of the carb intake adapters.

  9. #9
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    Quote Originally Posted by jim_in_dorris View Post
    Grease, If I was using a 454 TB, I would use the adapter that GM used. All 454 TBI's were mounted to 4 bbl carb intakes. Attachment 8942Attachment 8943

    I would use the 350 bin, what ECM are you using?
    Jim, it's funny you mention all TBI big blocks being carbed manifolds with an adapter. This one didn't. I funny planned to take the adapter when I sold the longblock. The only issue with using a factory one is my intake is the factory adapter was for a spread bore, and my Edelbrock 7116 is square bore.

    Either way I go, I'll be using the same 7427 PCM.

  10. #10
    Fuel Injected! jim_in_dorris's Avatar
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    I would use a square bore to spread bore adapter, then the 454 tbi to spreadbore adapter. I honestly didn't know that GM didn't use the adapter on all 454's. I plan on using mine with the 454 tbi and the high flow low pressure 454 injectors when I build my next engine for my truck.
    Square body stepsides forever!!!

  11. #11
    Fuel Injected!
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    Quote Originally Posted by jim_in_dorris View Post
    I would use a square bore to spread bore adapter, then the 454 tbi to spreadbore adapter. I honestly didn't know that GM didn't use the adapter on all 454's. I plan on using mine with the 454 tbi and the high flow low pressure 454 injectors when I build my next engine for my truck.
    I have a factory TBI to square bore adapter that was on a 405 hp 502 Mercruiser in a houseboat.

  12. #12
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    Are there any advantages over these choices with the Mercruiser piece?

    http://m.summitracing.com/search/dep...erial/aluminum

  13. #13
    Fuel Injected!
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    Quote Originally Posted by Greasedog View Post
    Are there any advantages over these choices with the Mercruiser piece?

    http://m.summitracing.com/search/dep...erial/aluminum
    The 17-45 Holley is a good piece , have used many before I started machining my own.

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    2006 Forest river-Sierra 37' 5th wheel
    1999 Astro Van, L31 Vortec , 4x4 conversion
    1994 Pontiac Sunbird "Work ride"
    1993 K-3500 "Ex-diesel" 454/4L80E - '7427
    1992 454SS "Eh Stock" , Blower & '7427 swap .
    1992 S-10 434 SBC/Tremec - '7427
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 454/700R4
    1977 Olds 98 Regency 403/700R4

  14. #14
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    Quote Originally Posted by billygraves
    Trans cooler lines. Don't use any rubber hose even the SS Rubber. It fails. Use steel and or Teflon lined SS hose. Parker is cheaper than other brands, if you get a corp discount.
    just noticed this, dunno how I missed it before. I've got access to a place that can make me heavy duty high pressure hisses in any length and configuration I want. Parker swedged ends, Aeroquip
    Triple Crown hoses. I've used these hoses at a 3000psi working pressure on heavy duty tow trucks, with much success. I don't think I'll ever put them through as much stress as we did there, so they should basically last forever.

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