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carb -> tbi

Discussion in 'The Garage' started by budweiser_man, Sep 27, 2005.

  1. budweiser_man

    budweiser_man Registered Member

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    went out wheeling this past weekend went up a few hills and my truck was cutting out from lack of fuel. well being this is not my daily driver I can take if off the road for a couple of weeks and it is not a big deal.

    so is it worth it is the first question.
    who has done it?

    I have been around fuel injected vechicles and have been tuning them for a while, wiring is no big deal for me. I will be using the setup off of a 87 or newer gm truck. My trucks is a 74 blazer will the intake manafold work off of a tbi?

    here is a list of parts I have came up with so far of what I need

    intake manfold
    throttle body injector bank
    computer
    wiring
    linkage for the throttle and tranny
    fuel pump(s)


    other questions are:

    is there a intake pump?

    temp sensor?

    fuel pump relay setup when does it turn on when you crank or the key is in the run position?

    aftermarket setups?


    thanks
     
  2. k20

    k20 3/4 ton status

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    Location:
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    There is a temp sensor, mounted in the manifold, that send a reference to the computer. The fuel pump runs for a few secs when you turn it to run, to pressurize the system, and then begins running when you start it. The relay on the tbi trucks is on the passenger side of the firewall, near the distr. Depending on the trans, there may be another relay hanging next to it. I dont remember which is which, without looking at the wiring. The pumps are in tank units of course, and the tanks are different between carb & tbi I believe. Atleast in all the replacements I see 87+'s are different than the carbs.

    I think the tbi manifold will bolt up to your 87s heads, I think its just the vortecs it wont, but I have been wrong before.
     
  3. budweiser_man

    budweiser_man Registered Member

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    sorry for not saying before

    the truck is a 74 blazer

    350-t350-203

    would it be possable to run a external fuel pump with the carb fuel tank or would the pickup in the tank not be able to handle it?
     
  4. zero cool

    zero cool 1/2 ton status

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    Holley makes adapters to bolt a Throttle Body onto a stock manifold. At least a stock carter/holley squarebore pattern. I'm halfway through doing this to an AMC 360 in my trail rig. (edit: I just checked. You can get a q-jet manifold to TBI adapter so you don't have to change intake manifolds or stack adapters...)

    For sensors, you need the temp sensor (bolts into the water passage), knock sensor (bolts into the block), oxy sensor (in the exhaust). I think everything else is self contained in the throttle body and computer. The throttle body contains it's own bypass pressure regulator. Rebuild kits come with a new spring. Any fuel pump that supplies at least 15 psi and sufficient flow (I forget how much off hand) will work fine. You don't have to get a specific GM in-tank fuel pump if you don't want.

    Painless wiring (http://www.painlesswiring.com/) makes a good conversion wiring harness with all the plugs you need and instructions on wiring it up.

    Howell (http://www.howell-efi.com/) makes full conversion kits and sells some of their parts.


    edit again: There's a lot of usefull info and helpfull people over on the third gen f-body site that can answer a lot of TBI questions. http://www.thirdgen.org/techbb2/ Check the TBI and DIY PROM areas on the forum for information.
     
  5. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    I've recently put a '90 engine in my '78 using an external pump and filter. (Turbo City). I think a TBI manifold will fit your heads ok but the the middle 4 bolts holes and upper surface where the underside of the bolt heads touch down are wrong but can be 'modified'!!
    My best advice to you would be buy a COMPLETE set up from someone. (often for sale on our 'for sale' forum) as that conversion will 'nickle and dime you to death' if you only buy some of it first off.
    You want all the sensors (coolant, oil, knock, O2,map) fuel relay, EGR valve and solonoid (if you're running one) and the correct distributor and coil. Make sure the throttle body has got the TPS and idle air stepper.
    I use a Painless Performance loom but you may score a stock loom from who ever you buy the rest from and just use what you need from it. Personally I'd recommend the Painless one as it's soooo easy to use!
    If you do a search you'll find quite a bit on the subject.
    It's a bit of a long slog but well worth it in the end when you're going nose first down a real steep wet, slippery gully and your motor doesn't miss a beat....unlike your heart :D
    Good luck.
     
  6. uglyangelracing

    uglyangelracing 1/2 ton status

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    I have a complete 87 TBI if your interested? Just make me an offer.
     

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