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350TBI swapped for 454TBI

Discussion in 'The Garage' started by mtrdrms, Dec 15, 2005.

  1. mtrdrms

    mtrdrms 1/2 ton status

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    Has anyone done this? What do I have to swap besides the engine and TBI? Computer? Engine mounts? Radiator? Thanks
     
  2. 425 Xpedition

    425 Xpedition 1/2 ton status

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    Computer is the same. Only need to change the chip.
     
  3. 1-ton

    1-ton 1/2 ton status Premium Member

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    This is the same project I am going to be taking on. From what I have learned you will need to change the radiator, radiator mounts, fan shroud, and engine mounts. You will need a bigger 650 CFM (at least) TBI unit, and carburetor type intake manifold to TBI adapter. The control module and wiring harness should work as long as the engine is completely stock, but if you put a bigger camshaft in the engine, then you will need a custom tuned EPROM chip for your ECM, and more fuel pressure.


    I am sure someone will come along and disgree with me. No one ever agrees with anything I have to say.
     
  4. gmtech954

    gmtech954 Registered Member

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    tried it without swapping the prom in a friends burb and the rig ran like a bag of sh##. you need to switch both or you will def have problems.
     
  5. 1-ton

    1-ton 1/2 ton status Premium Member

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    The ECM question all depends on what engine you are going to swap with. In order for someone to give a correct answer, they need more details. For example, the ECM that controls the 350 TBI on my 1991 V3500, is the same ECM that would control the Mark-IV, TBI, 454 (LE8 engine option), if it had come with one. But if I where swaping in a vortec head, Mark-VI, roller cam 454, it would not work. And if you plan on putting any type of decent low to mid-range performance RV camshaft into your engine (which almost every one does) all bets are off on what type of factory EPROM is going to work on your engine.
     
  6. d'cheat

    d'cheat Registered Member

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    You need the chip from the TBI 454. The computer is located behind the glove box. There is a little access panel on the top of the cumputer. Pull that off and you will see a blue box with PUSH on it. This is the brain of your rig. Pull that from the 454 and swap it into your stock computer. thats all you need. The 454 computer will not bolt up to your stock 350 harness. You can only use the chip.

    Now, the radiator all depends on what stock one you have. There are 2 core radiators, and 4 core radiators. My rig has a 4 core stock, so that should be plenty of cooling. A 2 core barely keeps the 350 cool. Swap it out!
    It helps that I am also installing Dual Black Magic electric fans. Over 5000 cfm. :D

    Motor mounts: what ever the big engine has, will bolt right up. Replace the rubber mounts on your rig while the engine is out. If they are not allready worn out, they will be soon.

    Exhaust will bolt up stock like. :)

    Depending on the year TBI your swaping to, and from, you may run into one minor issue. Some of the TBI engines have diffrent connectors on the throttle body. Dont fret, you can splice them from one to another. Or, you can buy an adaptor. For the life of me, I cant recall the link to the place that sells that. Hmm... Do a search and Im certain you'll find out who.
    thats perty just about it.
    Its realy easy. Everything else is direct bolt on.

    Best of luck man!

    D'cheat
     
  7. Russ

    Russ 1/2 ton status

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    I am doing this exact same thing right now. I have a TBI 454 (actually a 489 stroker) hanging on the engine hoist right now under my carport that I am putting in place of the TBI 350 I just took out.

    I went ahead and used the computer and wiring harness from the 454 as the harness routed around the engine completely different from the 350 harness. Also there were a couple of things (ESC?, Knock) on the 350 harness that my 454 did not have. There are a couple of connectors that you will need to swap if you want to use the 350 harness as they are molded differently from one engine to the other. Carquest has a catalog and sells the weatherpak connectors, but they are expensive (I know as I replaced all the ones on my harness that looked bad).

    I am finding that the hard fuel lines from the TBI down to the frame are a little short for the 454 engine. I am going to try and pick up a correct set today from the Chevrolet place.

    I managed to find a set of the correct motor mount frame brackets for the 454 from the Chevrolet dealer also. I compared them side by side and they are the same physical shape, but the holes are drilled higher and in a different pattern on the 454 frame brackets since the 454 clamshell mounts are larger than the ones on a 350. The big 454 mounts would not bolt up to the 350 frame mounts and vice versa.

    BTW, this is in a 1988 crewcab dually. The 454 engine I am swapping in is from an 88 also.

    Russ
     

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