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  1. #1
    Lurker


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    Feb 2014
    Name
    Corey
    Vehicle
    90 C1500 SCSB
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    79

    Default LT1 TBI-Just for grins and giggles.

    OK, I screwed up when I rebuilt the top end of my 5.7 a year or so ago, and after swapping on the higher compression Vortec heads, I also switched over to Mobil 1 synthetic oil. Ive since been told this is a no no. At least Im doing my part for mosquito abatement..... Anyway, it has caused me to start thinking about what to do with my motor-rebuild it, or replace it. So, I have a 94 LT1 with aluminum heads, that has been sitting at the machine shop for a while waiting for me to give the green light. After a bunch of research, I came up with an idea. Thought I'd run it by you guys to see if I missed anything.

    So, my LT1 will be .040 over, and Im going to run the Lunati LT4 hot cam. Specs are 218/228 at .050 with .503 lift with 1.5 rockers. I'll be running 1.6s for .5635 of lift. I was originally going to run a TPI setup, but it would require running a 411 ECM and I have too much money at the moment in an EBL setup that I have the tuning software for already. I got to looking at the dual plane 4V intake from GM performance, and with a carburetor, it pulls 30 ft.lbs. over a stock LT1 setup. As I am already running a 4V manifold with adapter under my TBI, the thought occurred to me that the LT1 dual plane with a TBI could work out real well. Not only does it have the low end grunt of a TPI, but also breathes well into the 5800 RPM range-unlike the TPI. The cam is also good from 18-5800 RPM so that looked like a good fit too. This manifold will also let me run the stock distributor getting rid of the Opti-crap and send the proper signals to my ECM. The 10.5:1 compression with keep the efficiency up too and I should get just as good or better mileage than I do now.

    I put the numbers into my desktop dyno-including complete flow numbers for the LT1 heads and 490 CFM for the TBI. At the rear wheels its showing 416 ft.lbs. at 3000 and 337 hp at 4750. If I replace the TBI with a 454 unit, at the rear wheels, I get 426ft,lbs. at 3000 and 346hp at 4750. Looks like the throttle body will naturally limit over rev.

    Any thoughts?
    Last edited by Ccreddell; 06-21-2016 at 10:26 AM.

  2. #2
    LTX Master


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    Nov 2008
    Name
    Enrique
    Vehicle
    93 Z28
    Location
    Houston/Clear Lake
    Posts
    615

    Default

    I can't read your post written in black font....
    93 Z28, 383, PI 3200, Strange 12 bolt, 3.73, Strange coilovers, suspension, and going 24X... for three years or so.


  3. #3
    Lurker


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    Join Date
    Feb 2014
    Name
    Corey
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    90 C1500 SCSB
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    Default

    Sorry, that should work better...

  4. #4
    InActive Member


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    Nov 2013
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    1997 K1500, SS/SB
    Location
    Kansas
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    199

    Default

    Quote Originally Posted by Ccreddell View Post
    OK, I screwed up when I rebuilt the top end of my 5.7 a year or so ago, and after swapping on the higher compression Vortec heads, I also switched over to Mobil 1 synthetic oil. Ive since been told this is a no no. At least Im doing my part for mosquito abatement..... Anyway, it has caused me to start thinking about what to do with my motor-rebuild it, or replace it. So, I have a 94 LT1 with aluminum heads, that has been sitting at the machine shop for a while waiting for me to give the green light. After a bunch of research, I came up with an idea. Thought I'd run it by you guys to see if I missed anything.

    So, my LT1 will be .040 over, and Im going to run the Lunati LT4 hot cam. Specs are 218/228 at .050 with .503 lift with 1.5 rockers. I'll be running 1.6s for .5635 of lift. I was originally going to run a TPI setup, but it would require running a 411 ECM and I have too much money at the moment in an EBL setup that I have the tuning software for already. I got to looking at the dual plane 4V intake from GM performance, and with a carburetor, it pulls 30 ft.lbs. over a stock LT1 setup. As I am already running a 4V manifold with adapter under my TBI, the thought occurred to me that the LT1 dual plane with a TBI could work out real well. Not only does it have the low end grunt of a TPI, but also breathes well into the 5800 RPM range-unlike the TPI. The cam is also good from 18-5800 RPM so that looked like a good fit too. This manifold will also let me run the stock distributor getting rid of the Opti-crap and send the proper signals to my ECM. The 10.5:1 compression with keep the efficiency up too and I should get just as good or better mileage than I do now.

    I put the numbers into my desktop dyno-including complete flow numbers for the LT1 heads and 490 CFM for the TBI. At the rear wheels its showing 416 ft.lbs. at 3000 and 337 hp at 4750. If I replace the TBI with a 454 unit, at the rear wheels, I get 426ft,lbs. at 3000 and 346hp at 4750. Looks like the throttle body will naturally limit over rev.

    Any thoughts?
    Most of the guys here only think HP HP HP , torque is a foreign to them as braille

  5. #5
    Lurker


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    Offline
    Join Date
    Feb 2014
    Name
    Corey
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    90 C1500 SCSB
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    79

    Default

    That may be true, but there is expertise here too. And, most people know that you can only measure torque, and that horsepower is an equation....

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