LT vs LS

Discussion in 'High Tech Retrofits' started by Camaromurph, Jan 5, 2019.

  1. Camaromurph

    Camaromurph Veteran Member

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    Hey all - Anyone doing LT swaps yet? I love the LS/T56 in my 68.

    Since the engine and trans in my new 79Z28 are not original I was thinking LS3/6L80E but have been doing some research into LT1/8L90E. I know that in either case the trans might be a bit of a stretch from a ground clearance stand point but will use a T56 Magnum or 4LXX as a fall back. I plan to keep the car stock ride height so not sure how much of a concern these auto trans' will be. I have read people with lowered cars have ground clearance issues but I don't plan to lower. On to the LT vs LS question.....

    For anyone that has done the LT swap so far what are the significant differences that may pose roadblocks compared to the LS swap.
     
  2. SPG

    SPG Bumblebee Builder

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    I've looked into this a fair bit
    Most people will tell you to do an LS swap because it's been around forever and there is significantly more support and you can get blocks for far cheaper in junk yards as they're more common.
    LT engines are fairly new (excluding the ones in the 90's...no one really uses those though) so they offer less support and if you have questions it will be harder to get answers. But as time goes on this will be less of an issue, but as of right now they come with a price premium, so most people will heavily push you towards and LS, your wallet, your money really.

    In terms of transmissions, from what I have found they're both similar sizes so any issues you have with one, you'll have with the other. You'll have to cut up car to get it to fit as it's larger than your th350. Here is a helpful page with measurements


    I'm putting an lt4 in my car, primarily because I just want to and think it would be cool, for more budget minded people an LS is the way to go.
     
  3. badazz81z28

    badazz81z28 Veteran Member

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    If its between a LS3 and a LT1, a LS3 is a no brainer IMHO...There is no significant performance advantage over the LS3 and there is much more aftermarket support to get a LS3 up and running in your car and will cost less in the end (zero headaches and guess work). On the other hand...cost per HP is better served with the LT4 (even over a LS7). Where are you gonna get 650hp in a crate engine form for $13,500? Its a pretty good bargain considering you just drop it in and go...No tuning not to mention it will not drive like a cammed/aggressive engine. I know someone will chime in about have a LS1 that makes 650hp, but its not going to run smooth and idle at 750rpms. I would go that direction if I could do it all over again (which maybe I will one day)
     
  4. SRGN

    SRGN Veteran Member

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    LT is direct injected. If you want to make more power than stock, you are bound by the limits of the stock fuel system, unless you budget a lot for fuel system upgrades. The way around has been to use a set of intake manifold mounted injectors, run by a second fuel system, controlled by an aftermarket ecm. The second set starts to come in when needed to compensate for the stock fuel system limitations. If you eliminate the direct injection, there is not much advantage to the LT platform over the LS.
     
  5. badazz81z28

    badazz81z28 Veteran Member

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    GDI is not good for the valves....I think there are some sacrifices for that little bit of gained power
     
  6. SRGN

    SRGN Veteran Member

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    Biggest problem we've been running into is carbon buildup on the intake valves. Without the atomized fuel spray to wash away oil running down the valve stem, or cool the intake valve, the result is a very nasty valve and intake port. It is quite common on GDI engines, and expensive/time consuming to resolve. In the car, we generally remove the intake manifold and blast with walnut shells to break up the carbon deposits.
     
  7. Camaromurph

    Camaromurph Veteran Member

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    Great discussion so far everyone. I have read that intake valve issue on the new GDI engines as well. I have to admit the only reason I started looking at the LT1 is it seems to be the only engine the GM crate engine and trans combo comes with the 8L90E. The 8L90E is slightly shorter centerline of shaft to bottom of pan and with all the ground clearance issues I’ve read about online with the 6L80E every inch would count. The 8L also seems to have been put on a diet compared to the 6L. The HP difference between the LS3 and LT1 is not important for my project.

    Since the Z is well equipped my plan was to make it a great cruiser with all the amenities. My 68 is nice but without AC or PW and such I hesitate to drive it to work during the summer months. Goal for the 79 would be to be able to drive it any day hence the AC and PW and reliability and mileage of the newer Powertrain.

    SPG - great build thread. I’ll be folowwing your progress. I don’t plan to start buying until April so I have time to follow others projects and do more research before I pull the trigger.
     
  8. Camaromurph

    Camaromurph Veteran Member

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    Oh, and I forgot to mention, stock appearing outside and inside as the reason I bought the car is for a Fast Times at Ridgemont High recreation. The car I bought is already correct for the movie car except stripe color.
     
  9. SPG

    SPG Bumblebee Builder

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    In that case you'll want to get a built up 4l60e, there are a lot of mixed options on that so I'm not going to recommend anything specific. a 4l80e will still require you to hack up the inside of your car. (at least from everything I have found)
    As for the t56 I don't know enough about it to comment, I just know the magnum will require you to hack up your interior, I don't know if that's also true for the older ones off an LS1

    Also what movie car are you making?
     
  10. badazz81z28

    badazz81z28 Veteran Member

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    The Magnum fits in the sec gen with ease, not so much for the F-body version. I hacked my floor brace for the f-body trans...very heart breaking
     

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