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Thread: 305 to 350 engine swap question

  1. #1
    Ultra21
    My buddy just blew his 305 in a deck boat and can get a killer deal on a crate 350 long block. The 305 was a TBI motor and I was wondering what problems we're going to run into in the swap. What specific 350 components will be needed to keep the TBI in place. I'm thinking it might make more sense to get a Holley 600 and HEI distributor and keep it simple. The 305 is a 1997 and the 350 is the same generation so the intake manifold will bolt right up. (I don't know what the gen is yet but will find out) Any thoughts on this.
    Thanks in advance.

  2. #2
    Moneypitt
    Should be a direct bolt in, everything should fit from the 305 to the 350. MP

  3. #3
    Ultra21
    I was wondering about the computer, anti-knock and the TBI which seem to be engine specific. If we have to change things like computer and TBI, or anything else that could get to be a pain and expensive, would it make more sense to just simplify things and go without the FI? dump the computer and go with a carb and distributor? I'm worried we'll get half way down the road and get hung up on something.

  4. #4
    396_Z
    The knock sensor has to be changed, thats the only absolute thing. You may or may not want to change the actual injectors for the next size up. It just depends on how hard and long your bud plans on spinning the 350. The cheap upgrade for the TBI has always been using a 454 TBI since it does have larger injectors and flows better.
    Everything else is 100% interchangable.

  5. #5
    75spectra
    If this is a factory mercruiser TBI then it already has the 454 TBI unit on it. Mercruiser never used the small TBI unit. It should have the TBI bolted to an adaptor plate that sits on either a 2bbl or 4bbl manifold. Get the 5.7 knock sensor and use the cam out of the 5.0 unless you know what cam the crate motor has?

  6. #6
    Kindsvater Flat
    As long as the heads are late model (center bolt valve cover) the fuel system should be able to compensate for the larger cubes which isn't much if the engine is stock.

  7. #7
    Ultra21
    The motor is a later model with the center valve cover bolts (both engines). Do you know where the knock sensor is located? I was thinking it's in the ECM but am not sure. Also, how can I tell if it's a smaller TBI or the 454. It has a 4 barrel manifold with an adapter if that helps. I'm going to take a look at the manifold tomorrow and try to determine which unit it has on it. It is a stock 305 Volvo Penta motor in a Monterey deck boat.

  8. #8
    396_Z
    The knock sensor is mounted to the bellhousing flange of the block, just off the the side of the dist usually.
    Tell the incompetant assistant at the parts store you want one for 96 or so chev truck with a 5.7. If you ask for a tree-fiddy knock sensor he won't know what you want usually.

  9. #9
    Kindsvater Flat
    The knock sensor is mounted to the bellhousing flange of the block, just off the the side of the dist usually.
    Tell the incompetant assistant at the parts store you want one for 96 or so chev truck with a 5.7. If you ask for a tree-fiddy knock sensor he won't know what you want usually.
    Don't forget if its not in the computor they don't make it. Well at least thats what they tell me.

  10. #10
    396_Z
    We won't discuss how many "assistants" I've had out on the floor looking for the correct rear wiper blade for a 77 chev pickup, or in the back looking for 83 corvette parts.

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