LT vs LS

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

  1. SPG

    SPG Bumblebee Builder

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    if you're comparing the 90's LT to current LS then yes, an LS is better
    but he's talking about a gen V LT engine which comparable (and some would argue better) than an LS. Current generation LTs will be the future and will become more and more common and eventually get the aftermarket support an LS has

    LS are popular because they're in everything and it's easy to get parts, LTs are so new they have less support...but slowly but surely.
     
    dave@ztech likes this.
  2. badazz81z28

    badazz81z28 Veteran Member

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    If you break it down....The LT is an LS variant. The LS was a clean sheet design over the SBC. I don't see the LT as a "better engine" (Not yet anyways). As time goes on the LT will become more popular as GM transitions to all their vehicles getting the LT engines. Right now the aftermarket is very supportable of LS engines and new crates are affordable and easily accessible to many budgets. I could ne wrong...but I highly doubt in 10 years cars will have LT engines like cars have LS engines today. I think LS will still be widely used and more popular than the LT engines.
     
  3. linenoise

    linenoise Veteran Member Lifetime Gold Member

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    I am with badazz. LT was a leap into new tech. the one after it might be better but it did not give enough power or justification for those extra parts and complexity. Now the LT5 supercharged version(https://www.jegs.com/p/Chevrolet-Pe...rged-62L-755-HP-Crate-Engine/7118244/10002/-1)
    750 HP supercharged would work. but than you got all the super charger parts and weight.
    Thats why I went big cubes. you know what they say in the bone yards, there is no replacement for displacement. Low rpm power rules for seat of pants fun.
     
  4. 76z28

    76z28 Veteran Member

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    How as your t56 install?
    I know you have a different frame etc, but I am curious.
    I am going to be installing one into my car and had a few questions about shifter location. Where did yours come up?
    Mine will be behind a big block making around 530 to the wheels, similar to your ls7 I think. How do you like it?
     
  5. BrewInfusedYeti

    BrewInfusedYeti New Member

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    I just started the process of gen V LT1 swap for my 2nd gen Frankenstein. I'd agree it is a bit more difficult to track down brackets and parts, however, due to an extremely similar block design to the LS3, most accessory kits transfer over with the use of the LS3 waterpump and LT1 truck harmonic balancer. Wire harnesses are marked up a bit as it's new tech but not by much. The reason I went LT was price, my donor block and 8l90 was ~500 more than an L99 with 6l80 that had more than double the miles. (26k vs 70k miles) dirty dingo supplied me with motor mounts that tie into the clamshell mounts and according to their site the trans tunnel should accept a 6l80 without modification (no notes on 8l90). I'll find out pretty quick if I need to cut the trans tunnel.
     
  6. badazz81z28

    badazz81z28 Veteran Member

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    If you can hunt them down the SC engines LT4 and LT5 are nice engines that you wouldn’t need to do any upgrades too. If the time comes, I think I’ll still want to stick with the LS. Make the 427 a 440.
     
  7. hot72rod

    hot72rod Veteran Member Gold Member

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    There is a little confusing going on here, The OP started talk about a 6L80 and a 8L90. These 2 trans are large in size and will require tunnel mods.

    Then the 4L60 and 4L80 were brought up, I can tell you from experience that these will fit into the trans tunnel with no problems.
     
  8. BrewInfusedYeti

    BrewInfusedYeti New Member

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    Take a look at this:
    https://paceperformance.com/p-28983-gm-transmission-dimensions.html

    The dimensions differences between the 4L60, 6L80, & 8L90 are minimal length wise. The biggest problem is height, with the 6l80 and 8l90 being ~2" taller than 4L60.

    This post from another site shows a 6l80 going into a 2nd gen without tunnel mods:
    https://www.pro-touring.com/threads/108673-2nd-gen-F-body-w-6L80e
    There's tons of photos and the trans has adequate clearance with the car at stock height, at the lowered front end stance there was not adequate clearance (~2.5").

    The 8L90 actually has a shallower pan then the 6L80 and is shorter height wise ~.25". Length of the trans from bellhousing to tailshaft (F in the diagram) is 26.795", it matches between the 4L60 and 8L90. The biggest problem is the height of the trans mixed with the stance of the vehicle. If you are running a stock height vehicle, you are safe to run a 6l80 or 8L90 without tunnel mods. Once you lower the stance on the front, expect to be close to the ground and expect to cut the trans tunnel to accommodate pushing the trans up into the car further.
     
  9. hot72rod

    hot72rod Veteran Member Gold Member

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    When I say bigger in size I'm not referring to length. I'm talking about the dia. of the main body.

    Also thy are using BRP mounts which put the motor in the stock position of a sbc, that was a big benefit for them. Lets face it not everyone is using a $500 swap mount kit from BRP.


    Here is a quote from the page you linked to.

    "I'm surprised I haven't found this thread. I put a LS3 6L90 under my 71 trans am clone. The 6l90 is huge and has awful ground clearance. I raised my trans tunnel as much as 3" in some areas and raised most of the driveshaft tunnel. I have my motor a lot farther back which required more work. I honestly dont think the 6l80/6l90 will work well with out major modifications."
     
  10. RattleCanZ28

    RattleCanZ28 New Member

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    Just to chime in... the new LT 8L series are even larger than the 6L series. When you look at the 6l80 cars (my old man has a 2010 ss) and the way the cars are setup... the engines and transmissions intrude much further into the cabin than the small hump that is in the 2nd gens. The control of the 6L/8L series is MUCH more complicated. I went through The Tuning School's 6L trans tuning class along with the GenV LS platform and there are exponentially more controls related to those transmissions. I've only seen one stand alone controller for the 6L's and nothing yet for the 8L's. So standalone controls for the 8L series is pretty much a no-go.

    As for those that are looking at the L86/L83 (LT gen V truck versions). The cranks in the L83's aren't provisioned for a manual. The L86 that I looked at for my 73 RS did have one, but the pilot bearing hole needed to be honed out a bit for the TR6060 to fit properly.

    The direct injection system will handle anything but large amounts of boost. If you want to throw a procharger at it and rock 12psi... the stock injectors will work fine. You don't have to calculate for TAU (gas build up on the intake runner that gets boiled off before it's used in the combustion process) and the precise command of the DI injectors allow for a much high AF ratio.

    For those that want to run turbos with large amounts of boost, you'll have to look at a secondary injection system. I don't believe the OEM ECM will handle this, but most of the larger name ECM manufactures can be piggy backed to handle this.

    The "Bad for the valves" is just that oil vapor gets coked onto the back of the intake valves. Stock DI systems don't spray fuel onto the back of the intake valve to keep it clean. If you go with a secondary fuel injection system, this mitigates the majority of this. For stock systems, you can install a "catch can" system that pulls the oil vapor out of the PCV system so that it doesn't accumulate in the intake tract. (Still happens.. just not as much)

    Along with my 73 RS, I own a Focus ST as a daily driver. So boosted DI engines is no new thing to me.
     

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