Converting TBI to carb question
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Converting TBI to carb question

  1. #1

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    Default Converting TBI to carb question

    I have a 97 Gen. VI with throttlebody injection and would like to convert to a carb setup. I figure the distributer would need to be changed to a vaccum or mechcanical advance unit. Anybody know what else is involved? I figure the electric fuel pump would need a regulator to get the psi down to 7-9 lbs. I believe at present it's putting out 30 psi. Any help would be greatly appreciated. TIA

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    i have converted carb engines to tbi. there is not much difference between the two. fuel pressure for tbi is 14 psi. a regulator may work but a tbi pump is supposed to have a return line to the tank so the pump is not overworked. bottom line, replace the fuel pump with a low pressure carb pump, swap the intake manifold and carb, remove the sensors and run it.

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    Thanks Sac, what about the distributer and the ECM? Do you just unplug and remove the ECM? The only sensors I'm seeing is a knock sensor and a water temperature sensor not including the ones to run the TBI unit map, iat, etc. The ECM is running the spark advance in the distributer thats why I was asking about having to replace the distributer. I would use an MSD marine distributer. Thanks for your input, doesn't sound like much is involved for the swap.

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    Don Johnson Don Johnson's Avatar
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    I have been looking into this convesion as well for an old Suburban I have. I believe you will also have to add a TPS, throttle position sensor, so that the computor can run the transmission. Otherwise add the aftermarket tranny computer which is expensive...

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    Don I'm looking into converting the boat motor from TBI to carb. Now going the other way with a vehicle is easy, many vendors have the complete kits, wiring harnesses, and stand alone ecms. It's done frequently in the Corvette world, LT1, LS1, etc. engine swaps into older noncomputer Vettes.

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    cfm
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    The computer controlled distributor from GM - ie: the 'external coil HEI' one used in many marine and all GM 87-95 V8 TBI engines - has a module inside that has a very good performance advance curve.

    Therefore, you do not need to replace the distributor.

    Yes, I have used it multiple times in carb'd applications.

  9. #7

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    Thanks CFM I'll be sure to keep that in mind, but if I remove the ECM where will the distributer get it's signal from to advance the timing?

  10. #8
    cfm
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    It's a magnetic pick up distributor that feeds the signal into it's own module. It's all self contained other than, of course, it's remote mounted coil.

    Again, the module provides it's own advance curve. When you set timing, set the total which I believe is all in around 3k. The beginning advance starts early so don't set timing by that. You'll have to double check but I think the total advance is around 20°-22° degrees.

  11. #9
    21 Daytona Outlaw's Avatar
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    does it have injectors in the throttle body?
    #55

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    Quote Originally Posted by Outlaw View Post
    does it have injectors in the throttle body?
    Yes, it's the basic two injectors in the TB.

  13. #11
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    Install an intake manifold, HEI distibutor (stand alone), carb, flame arrestor, 7 lbs electric fuel pump, and throttle cable bracket. Use your old thermostat housing, water trap fuel filter and temp sensors. Remove ALL the EFI stuff and sell it to me! CHEAP! PM me if your EFI stuff is for sale.

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