L31 to LT1 swap?

Discussion in 'Engine Performance + Maintenance' started by Hobie, Jan 13, 2020.

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  1. Hobie

    Hobie I'm Awesome

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    I got an offer today for a LT1 out of a 96 Corvette. The car had 38k miles, and was wrecked. The engine will include intake to oil pan (I'll try to get the accessories as well,) engine harness, and the PCM.

    Now my L31 is on its last legs, oil pressure at idle is around 10 PSI, and leaks oil from about every point possible, and it sounds like I've got some piston slap.

    I do have another L31 that I've tore down, but havent given the machine shop the go ahead to start on the block and heads. So since this LT1 has come up, I'm considering the option heavily.

    I have a 411 PCM ready to send off, and I'll go with a basic rebuild on the LT1 if I grab it. I will also be swapping it to a 24x setup to get rid of the opti spark ignition.

    I've looked around on here, and I'm not seeing anyone who has done this swap, although I have a feeling someone has. What kind of headache would you guys reckon I'll be getting myself into if I go ahead and perform this swap?
     
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  2. McBroom

    McBroom OBS Enthusiast

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    As long as you get the wiring and pcm it's a breeze.
    I think the most difficult part is the motor mounts. Might have to turn them around. If ya pass on this deal pass it on to us.

    The Blue Mule
     
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  3. Supercharged111

    Supercharged111 I'm Awesome

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    Motor mounts ought to be fine as is I would think. Lucky you, the 411 can run the OBDII LT1.



    FWIW I unplugged my cam sensor and drove around for a couple weeks and noticed zero change in driveability or mpg.
     
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  4. Hobie

    Hobie I'm Awesome

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    I'll have to see if I can find run-out diagrams for both the 411, black box, and the PCM in the Vette.
    On the motor mount part, arent the Gen1 and Gen2 small block the same mounts?
    And if I do pass it up, I'll definitely be posting it up on here for one of yall to grab!
     
  5. Hobie

    Hobie I'm Awesome

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    @Supercharged111 I was figuring the LT1 would be able to run with the 411, I'm sure there will be compatibility issues somewhere in the swap, and that's the biggest reason I'm asking for advice right now. It's going to be a headache for sure, but it sure would be cool, and different!
     
  6. Supercharged111

    Supercharged111 I'm Awesome

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    I neglected to specify in my last post you don't need the expensive ass 24x to run the LT1 on a 411 and delete the opti. Watch the first 2 minutes of that video. It is stupid cheap/easy to run the LT1 off the 411.
     
  7. Hobie

    Hobie I'm Awesome

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    A few issues I see after watching the first 5 minutes. Although the 24x can be expensive, I would assume a lot more tuning capabilities can come from it, just as adding a 24x to a factory L31. But the guy explains that he stabbed a vortec distributor into his LT1, but I thought the LT's didnt have a hole in the back of the intake manifold, but did have the bore in the block, if another intake was added, a distributor could be used.

    Also, would it be wrong to assume the 24x cog/crank sensor from a LS based engine would work on a Gen1/Gen2 small block?
    I havent looked into the fine details on the size difference between the two, but I would assume they are fairly close, if not the same. Maybe next time I'm at the J/Y I'll see if I can grab a cog, and measure it as well as the one piece crank I have laying around
     
  8. L29Sub

    L29Sub I'm Awesome

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    '96 Vette should be an LT4. Much better engine. Should have s red plenum and aluminum heads with "D" ports.
    As stated, the motor mounts are about 2" forward of other cast iron SB block engines. A flat plate will adapt. Probably S10 conversion mounts will also work.
    Install a new Optispark and plug wires. The opti is an issue in the waiting. A real PITA to get to. Otherwise, excellent engine. They run cooler due to reverse coolant flow.
    If you find cast iron heads, it isn't a Vette engine. Caprice and other B cars had cast iron.
    Aluminum heads on Camaro and Vette.
    Not all LT1s are 5.7. Some are smaller. Run the numbers. 9C1 was the only good cast iron head LT engine.
    The red plenum 96 was the best.
    Grab the fuel lines too. They are oddities.

    Sent from my SM-G965U using Tapatalk
     
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  9. Hobie

    Hobie I'm Awesome

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    The Corvettes in 96 had three options, the LT1(auto cars), LT4(Grand sports), and LT5(ZL1). Now, this engine is an aluminum head, silver intake from an auto Corvette, so an LT1 would be the designation.

    Engine mounting will be looked into more, and thank you for updating the info that I have seen being 2" foward. I will look into S10 mounts, and possibly reverse camaro/corvette mounts?

    Due to having to do two tune ups on a family members LT1, I will refuse to keep opti spark, yes they run very well, but I will not have that design in a daily driver, that's just plain stupid honestly. I do enjoy the lower coolant temps than a traditional Gen1 small block, and I love the reverse cooling design.

    The 4.3 L98 I believe is what you are mentioning about the smaller engines, and personally, I wouldnt mind either or. Although the 4.3 would have to be built differently than a 5.7 due to the displacement, but we had a 4.3 V8 in a 48 chevy. It had tons of power, and a safe redline of 7500RPM.

    The engine has not been pulled from the car yet, I'll be going to look at it this weekend to see how it runs, and the overall condition.
     
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  10. Supercharged111

    Supercharged111 I'm Awesome

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    24x and 4x crank reluctors use the same OS, so identical tuning capabilities.
     

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