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454 to 350 swap

Discussion in 'Chevy Trucks' started by malibulxi, Sep 5, 2011.

  1. malibulxi

    malibulxi Junior Member
    Messages: 5

    I recently inherited a 1998 Chevy 3500 dually with a 454 vortec. The motor is shot, but I have a longblock 350 with less than 20k on it. (came from a roll over) Would this be a relatively simple process to swap? Would the transmission need to be swapped as well or would it be ok? Any other thoughts or suggestions would be great.

    Oh, one more question. How much of a fuel mileage difference would there be? If it's too much of a hassle, I may just rebuild the 454.

    Thanks in advance.
  2. MikeRi24

    MikeRi24 Senior Member
    Messages: 562

    I would rebuilt the 454. The 350 is a great motor, but thats a lot of truck for it. You're prob going to need the transmission to go with the 350, not to mention the engine computer, transmission computer and all the wiring harnesses....as I said, rebuilding the 454 sounds good to me.

    THEGOLDPRO PlowSite Veteran
    Messages: 3,136

    you wont likely see much over 7-8 mpg in the 454. its a total gas hog.
  4. malibulxi

    malibulxi Junior Member
    Messages: 5

    Yeah, I think you are right. I am looking at a rebuilt 454 with a 4yr/40k warranty for $1895 with free delivery from Maine. http://marshallsmachine.com/ has a bunch of motors available for many different vehicles.

    Before I jump in on a already rebuilt motor, any suggestions on where I can get a decent rebuild kit for my 454 online?
  5. MikeRi24

    MikeRi24 Senior Member
    Messages: 562

    If they are charging that for a rebuilt one WITH a warranty AND free shipping, get that. To rebuild your engine the right way, its going to need to be town down and have everything machined and thats probably going to cost you at least a grand right there, and then if the reason the engine blew was due to internal failure, there still might be something wrong with your block or heads. Then you're really out a lot of money. Even if you're able to find someone to the machine work on the cheap and it all checks out and you put it all together yourself, if something not EXACTLY right and 2,000 miles down the road it blows again, then you're really screwed. $1895 for a new one with a warranty sounds good to me...
  6. BlizzardBeater

    BlizzardBeater Senior Member
    from Maine
    Messages: 420

    I have to agree. That's a great price on a 454 rebuild and warranty. That warranty is the big ticket. Even the best builders can miss a bad block or weak journal or main once in a blue moon. With a warranty, it's one less thing to worry about.
  7. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    tranny will bolt up no problems to small block.

    but major problems is the obdII computer system. lots of stuff might need swaped for sensors from 1 to the other and reflash of the pcm to run the 350.

    also the full front engine drive system for pulleys and belts will be diffrent.

    so basicly by the time its done your money in the bank dropin in the same thing that was pulled on the newer 96-up vehicles unless you have a whole doner vehicle there next to it to swap from.

    fyi ask if the warrenty is gen person or comercial aproved. since you will be using this truck for work.
  8. Holland

    Holland Senior Member
    Messages: 605

    your looking at a considerable amount of work to swap. Trans would be fine, but you'd need to swap the pcm, harness, exhaust.... The list would go on and on. A complete donor truck would be easiest. And if your longblock doesnt have vortec heads you'll need them and a vortec intake to keep it fuel injected. i vote for to keep the 7.4. Just make sure you get a vortec replacement. Even if its just a shortblock you're getting. Or if your rebuild what you have, you have no worries! Good luck with whatever you decide!

    If you have any questions, i'm good with both the smallblock and big block vortecs. Our pulling truck is a 98 with a 7.4. Still a vortec and still fuel injected. Needed a bit of dyno tuning to make it run tho! So we've had it apart quite a few times!

    (little tip to, when you go to pull the 7.4 be careful with the egr tube. They're expensive and a dealer only item!!!)
  9. malibulxi

    malibulxi Junior Member
    Messages: 5

    Thanks for all the info! I think replacing the 454 with a 454 would be the best idea. Especially since it will come with a 4 yr/40k warranty. The warranty included is good for both commercial and non commercial uses. I suggest everyone looking for a rebuilt motor check out that company that I posted earlier in the thread.

    Thanks again for the info!
  10. mule585

    mule585 Member
    Messages: 74

    deff. stick with the 454 i love my 2 trucks with them. they will pull any thing you put behind them.im avg. 11-12mpg empty if i keep my foot off the pedal (which is hard to do) 7-9mpg with a full mowing trailer. overall great engine!!!