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tbi to carb sending unit?

Discussion in 'The Garage' started by shaun89, Apr 24, 2007.

  1. shaun89

    shaun89 1/2 ton status

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    im switching my 89 k5 from tbi to carb, so i has the fuel pump in the tank, and im putting on a mechanical one. will the mechanical pump be able to get the fuel out of the tank or will i have to switch to say... an '82 sending unit? cant find anything on it.:confused:
     
  2. k20

    k20 3/4 ton status

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    I just converted my truck from FI to carb (before anyone pwns me, I am a mall crawler and was getting tired of fixing random problems), anyway. I retained the electric pump. The tbi is just a 12-14psi system, so I bought a 3 port regulator from holley, set it to 6psi, and I have no issues.

    A mechanical pump wont be able to suck it through an electric pump if you are dead set on a mechanical pump.
     
  3. SkysTheLimit

    SkysTheLimit 1/2 ton status

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    I'm in the process of converting my 88 from tbi to carb as well. Here's what you need to consider and why I did it the way I did it:

    What motor are you running and what motor will you be running in the forseeable future. the stock TBI pump with a regulator as mentioned above will work fine for a hot 383 or a mild big block. I'm really interested in how K20's setup is working since he's got a 496 like me.

    I went with a replacement carb sending unit and an external high flow fuel pump. The reason being, I have a hot 496. I figured this was the safer way to go for flexibility in the future. (some sort of forced induction down the road) I haven't got it all buttoned up and running yet but I know this set up will work for sure.

    You got options.

    EDIT: forgot one point. If you swap sending units and keep your TBI tank, you will need to install it backwards due to the baffles being in the way. Or so I've read. I haven't installed mine yet.
     
  4. k20

    k20 3/4 ton status

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    So far mine seems to be workin flawless. I dont turn 5k+ for extended periods so fuel starvation isnt a problem w/ the stock TBI pumps. The TBI pumps are just sittin there hummin along and when the otherside of the regulator hits 6psi, it just bypasses and returns to the tank. Seems to be working wonderfully actually.

    The wiring was the biggest pain in the butt, but thats mainly b/c I hate wiring with a passion lol.

    I have a moderate big block, desktop dyno says ~470hp, ~600ft/lbs, its a low rpm thumper, but she will stretch her legs every now and then. It has a 850 Speed Demon sittin up top, and it has worked flawlessly for the 2 months its been on there.
     
  5. BizeeB65

    BizeeB65 1/2 ton status

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    I'm still interested in your TBI sending unit if you still have it! PM ME!! :D
     
  6. SkysTheLimit

    SkysTheLimit 1/2 ton status

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    Cool. I got a few more race parts on mine so I turn a little more revs. Got a 850 proform/holley carb for it. In the camaro it had a holley black fuel pump so i stuck with that. I read the TBI pump could starve at higher revs. Dyno'd in the camaro at around 800hp/700ft lb. I'm tuning it down a little for more street manners but didn't want to risk it leaning out.

    What'd you do with the MPFI system?
     
  7. SkysTheLimit

    SkysTheLimit 1/2 ton status

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    PM'd
     
  8. shaun89

    shaun89 1/2 ton status

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    i acutally have a 400hp crate 350 and tranny in my garage waiting for me, so i was guessing the stock pump from tbi couldnt supply it, and i got a 80gph mech. pump, and 770 truck avenger, so since i cant suck through the stock sending unit, what year should i get? its a 31 gallon tank if that matters. thanks for all the help guys, u keep my truck alive:bow:
     
  9. Steve GMC

    Steve GMC 1/2 ton status

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    what ever year befor 1987. as long as it is deep (and for a carb) enough you can use it.
     
  10. shaun89

    shaun89 1/2 ton status

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    ok.....thanks steven........
     
  11. SkysTheLimit

    SkysTheLimit 1/2 ton status

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    I FINALLY got my carb sending unit installed in my tank. I always read that you had to install it backward in the TBI tank because of the baffles. Well, that's not true in my case. The sending unit and tank are keyed. It would only install 1 way. Even trying to fit it in, it'd still hit the baffles anyway. The solution became apparent when I compred the TBI sending unit with the carb sending unit. Theres a bit of a jog to one side on the TBI unit so the sender doesn't stick out so far.

    The solution, bend the float peice 180 degrees. Then it fits down there perfect with the sending unit installed in its correct orientation.
     
  12. shaun89

    shaun89 1/2 ton status

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    ooo cool, thanks for the heads up man, did u eliminate any of the hoses going into the sending unit, or just buy the sending unit with the correct amount and attach them?
     
  13. SkysTheLimit

    SkysTheLimit 1/2 ton status

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    The sending unit I got was the 3 outlet. It doesn't have a provision for a return line. I'll leave the return in the frame rails and just secure the ends up out of the way. You never know what the future holds in store.
     
  14. shaun89

    shaun89 1/2 ton status

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    oo ok, thanks for all the help man.:bow: ill post some pics when i get my engine in!
     

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