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Swapping a 454 for a 350

Discussion in 'Chevy Trucks' started by Alaska Boss, Sep 20, 2008.

  1. Alaska Boss

    Alaska Boss PlowSite.com Addict
    from Alaska
    Messages: 1,951

    I have a chance at getting an early '90's 3500 reg/cab SRW (just like what I now have) in good shape, but with a somewhat worn-out 454. This would be a parts truck/back-up to what I have now, but I have a nice & healthy 350 (TBI) that I'd like to replace the 454 with. I haven't done any engine swaps since the '70's when everything worked in everything. For those that have actually done this lately, is this pretty straight-forward? I'm sure swapping the computer controls, etc., goes with the engine, but since the wiring etc is all the same, are there any other changes that one needs to do? (exhaust, motor mounts, fuel lines, CC, etc?). First-hand, hands-on knowledge would be appreciated. Thanks:salute:
  2. lawnmasters2006

    lawnmasters2006 Senior Member
    Messages: 215

    the easy way is to install an but on a carburetor ...same gas millage..been there done that...not sure if u wold have to change the frame mount on those year..i swapped a 350 tbi w a new crate mtor ...an but a carburetor on it
  3. brad96z28

    brad96z28 PlowSite.com Addict
    Messages: 1,525

    Same gas miles on a carb, ar u nuts? Carb would be a step in the wrong direction for sure. U all know how fun chokes are and how a great a carb runs on a cold engine I wonder why they went out in the 80s. Exhaust Is not gona be the same I dont think. Was the 454 tbi as well? It motor mounts I think are the same. U would just want to use everything possible from the 350, harness, computer, I just dont think the y pipe will be the same from a big block to a small block.
    Last edited: Sep 20, 2008
  4. Milwaukee

    Milwaukee 2000 Club Member
    Messages: 2,180

    Plus carb would not work great because he live in Alaska so it get very cold then carb would be work poor.

    I say it easy but get all wire harness and computer do not cut wires because many people get motor for sale found they cut all plug:angry:. So good thing I have same one junk 351W so we use that for replace 351W.
  5. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    for tons of good info on the older 73-87 trucks check out www.ck5.com. thay have a efi tech section for tbi type stuff. and tons of good info all around.

    and carb not tbi what are you smoking? :dizzy:

    i love my tbi get better fuel milage and tourqe is stronger with easy starting.
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    The 350 will physically mount right in in place of the 454 with no frame mount/trans mods whatsoever but...

    You'll need the 350 accessory drive pulleys and related accessory brackets as well as the TBI components. You can use the alternator and PS pump as is. Possibly the A/C compressor (if equipped) depending on exact year and which style of compressor the 454 has as there were a couple different styles through those years. You'll need a small block Y-pipe and fan shroud also.

    Is it a manual or auto equipped truck?

    The electronic side of it is where the specific years and components of the truck are going to determine how easy the swap will be...need more details.
    Last edited: Sep 20, 2008
  7. Alaska Boss

    Alaska Boss PlowSite.com Addict
    from Alaska
    Messages: 1,951

    The 454 has a TH 400 behind it,... I know that will bolt up to the 350 no problem, so everything that controls that should stay the same. I just found out now that the 454 is a '89, and the 350 is a '92. The 350 has all accessories with it, so nothing off the 454 would be needed. I thought if this wasn't too much of a hassle, I'd be getting the biggest radiator, coolers, etc that came on those trucks, so a 350 would never overheat anything. Thanks B&B
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Ok, the TH-400 and complete 350 makes it a piece of cake. Use an '89-'91 350 ECM and you'll be good to go.

    But you'll wish you had just freshed the 454. :nod:
  9. Alaska Boss

    Alaska Boss PlowSite.com Addict
    from Alaska
    Messages: 1,951

    I also have the original ECM that came with the '92 350,... are you saying that I can't use it, but need one from a 89-91? (Because of the truck?) By the way, how much difference is there in weight between a 454 & a 350? Thanks again
  10. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Depends on which style ECM the '92 is as '92 was the change over year (in the trucks) from the old Mem-Cal equipped ECM's to the next generation EEPROM ECM's. But if you compare the two and they look physically the same then the '92 350 ECM is the old Mem-Cal style and will work.

    Weight difference is approx 140 lbs between the small and big block.
  11. ServiceOnSite

    ServiceOnSite Senior Member
    Messages: 950

    not when hes looking at the fuel bill at the end of the week
  12. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Won't be much difference under plowing conditions.