LT4 swap in 1970 by GMPP

Discussion in 'High Tech Retrofits' started by C4Racer, Mar 3, 2021.

  1. C4Racer

    C4Racer Veteran Member

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    Anybody catch this sweet ride?

    https://gmauthority.com/blog/2021/0...usses-lt4-powered-1970-chevy-camaro-rs-video/

    Looks a lot like mine!!

    Got me thinking about doing a EFI swap actually. I have been toying with the idea of buying a C6Z06 with the LT7 and so I started thinking - hey, why not put one in my 71.

    But after crunching a bunch of numbers it doesn't make much sense. Crate LS7 is $3500 more than a crate SL3 and you have to do the heads and cam to either one for about the same cost - so you end up with maybe a 600hp motor vs. a 580hp motor which isn't enough difference to justify the cost.

    So then I looked into the LT4 - and was surprised to learn they have reduced the price point to $15K. Well - that's interesting. It requires a bit more in controller and fuel system mods - but it isn't all that bad.

    Bottom line it would take about $22K to swap in a LT4, or $17,500 for a built LS7 or $14K for a built LS3 assuming buying a new crate motor and GMPP harness. And then I could sell the existing engine for $4K ish to offset so it's $10K/$13.5K/$18K

    Given the power point and cost the LS3 route sure seems like the sweet spot to me.
    For a real world budget vs. a corporate budget.
    And would the LT4 really add an additional $8K of value to the car? Unlikely. But maybe some decent percentage of it anyway. Hard to say.

    [​IMG]71Cam8 by C4RACER, on Flickr
     
  2. SPG

    SPG Bumblebee Builder

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    Thats actually the 2016 HOT ROD Power Tour car they used to show off the lt4 crate engine
    it's pretty nice
    Untitled.png


    As for what you should do, I'm biased, but go with the LT4 (no actual argument for or against, I just like the motor)
     
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  3. BonzoHansen

    BonzoHansen Administrator Lifetime Gold Member

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    It was at sema last time I went. 2017 I think
     
  4. C4Racer

    C4Racer Veteran Member

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    I have a 2016 with the LT1 btw. Great motor but the 406 is still more fun to drive. I figure a LT4 would just be insane in the 71.
     
  5. badazz81z28

    badazz81z28 Veteran Member

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    I can tell you, adding a $15K engine to your car doesn't necessarily add the equivalent to the cars value. If it ever came time to sell it, a potential owner would have to understand and appreciate the cost and work involved. Most people care less of the engine that's in the car and more about about how much HP and how fast it is. Point proven on your comparison of the LS3 and the LS7. From a HP stand-point, they don't seem much different, but the LS7 is a very different engine with high RPM and track in mind. Comparing it to a street purposed LS3 is not even close with a cast crank, powdered metal rods etc...The LS7 is a more robust engine. The LT4 is the latest and trending engine with 650hp. An excellent choice for a street car and I think hard to beat for the money. The problem is aftermarket support, its growing but its super easy to install an LS in nearly anything. The LT you're gonna have to do some research on accessory drives, oil pans, bellhousing etc. Completely do-able. If I was going to do a street car, I would go LT4 and if it was a track car, I would build a LS7 and bump the cubes to 440. A $17,500 built LS7should have more power than a stock LT4. My LS7 made 650hp, and I done only a cam and head work.
     
    Last edited: Mar 4, 2021
  6. C4Racer

    C4Racer Veteran Member

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    Some good input there. I’ll send you a PM would like to pick your brain a bit more on the LS7 because I am not as knowledgeable on these engines as I would like to be.

    Seems to me the rpm range is mostly about cam and head flow and intake as long as the bottom end can support it.
    The bore / stroke ratio of a LS3 is better for RPM than a LS7.

    LS7 is 1.03
    LS3 is 1.12

    Old school 377 is 1.18 and 355 is 1.16
    Even my 406 is 1.1 and this is not known to be a rev motor.

    now maybe rotating assembly weight and rod length play a factor here too. LS7 has 6” rods which is a good thing but so does LS3. Nodular iron crank vs forged - rods aren’t as good - pistons are similar. Similar head intake size but the LS7 is a 12 degree valve vs 15 so potential for more flow there I would think.

    dry sump is something I didn’t think about. That could be the difference maker but also more painful to plumb ? Coolers ? These are some details I need more info on.

    as far as build goals - it’s more of a track capable street car. Not just a cruiser. I plan to do track days again and some autox events. And extending RPM over my current 6200 limit is a big factor. Also would like to hit around 600hp and NA is preferred for me as easier to drive on a track less cooling issues and the tires can hardly hold 500ftlbs from the 406 so a big TQ / area under the curve power plant won’t make the car all that much faster. It runs 11s as it sits today fwiw.
     
    Last edited: Mar 5, 2021
  7. C4Racer

    C4Racer Veteran Member

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  8. 72BIGBLOCK

    72BIGBLOCK Veteran Member

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    Yeah I saw that car at sema before
     
  9. badazz81z28

    badazz81z28 Veteran Member

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    The LS7s RPM capability is in the valvetrain with lighter valves. Having rods that weight about 30% lighter than typical steel helps too. The valve guide issues were a factory defect which I'm sure is not an issue with the new crates engines. Additionally, the failures were only early in life and very small percentage. I had my heads checked out because it was an 2008 engine and NO issues. Texas Speed put them back together with the stock guides.
     
  10. C4Racer

    C4Racer Veteran Member

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    Yes I was thinking GM must have fixed that issue if they are continuing to build and sell crate engines with a warranty.
    Might be worth a conversation with one of the shops that work on these heads.


    Also - this one uses the stronger bowtie LSX block and looks to me like the same LS7 heads. Comes with a 2 year warranty. The valve guides just can't be a problem on this engine - they wouldn't be selling it.

    https://sdparts.com/i-24502328-chevrolet-performance-19417357-lsx454-crate-engine-627hp.html

    Interesting motor too - because that makes 627hp as it comes at 6300, so I would think that motor can easily rev to 6800 even with the cam it comes with.

    That motor is also one I will consider.
     
    Last edited: Mar 5, 2021

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