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Thread: LS7 build done

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    Default LS7 build done

    For a F1c procharger starting at 15lbs frank at total power beefed up the lower end and drivetrain.Im slowly breaking in the engine and clutch.I will post dyno results soon. Cant wait to put the whistler to work.

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    Moderator catbert's Avatar
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    The dyno results will be interesting. It should be a beast, regardless.
    There are times for thinking, and times for acting, but the art is in the balance


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    LS7 build done 6 Shooter's Avatar
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    Default They run awesome, I remember my scoot in Art's...


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    Good luck with this project. I hope you won't be in a bad spot if the project has a major failure. I believe using the 427 LS7 block was a major mistake if the goal was max HP and Torque for this project. GM used the 6.2L block in the LS9 for several reasons. The main reason being that the cylinder walls are thicker and strong to handle the stresses under boosted conditions. I believe the LS9 is running about 10 psi of boost. Your adding about 50% more boost to a greater displacement. I don't know the expected HP gain but it will be substantial. Block failure will most likely occur over time. You may get ten good runs at the track and the eleventh would be a major catastrophic failure. The real question is how much long term boost will the engine handle before signs of a impending failure show up? Hard to say... My best estimate for long term boost level is 5-7 psi of boost. More boost would be asking for reduced engine life. Next issue...Why the Procharger? Its very noisy. This may bother if you have to listen to it for hours. My choice would have been the Edelbrock E-Force supercharger. Its like the factory unit on the LS9. It's a positive displacement unit that runs quiet and doesn't take up a lot of engine compartment space and fits under the stock hood. It's boost level is in a reliable range for long term usage.

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    "Z Wiz" is right.

    An LS7 on 15 PSI is a potential disaster waiting to happen.

    There are two main reasons a supercharger, especially one with that much boost, is problematic on an LS7.

    1) The cylinder walls are too thin. That's the main reason GM did not use the LS7 case for the LS9
    2) The compression ratio is too high. To keep the engine out of detonation is going to require either a very retarded spark schedule or racing gasoline.

    The only way to make an LS7 with a Procharger durable for a reasonable amount of time is not drive it under high boost.

    No doubt, you're going to move ahead with this project regardless of our comments so, let me offer a few last suggestion:
    Make damn sure whomever you have calibrate the engine controls understands the potential detonation problem and knows how to address it. Start with 100-oct unleaded racing gas in the tank, then back down the octane to pump gas as the calibrator reworks the spark schedule. The retarded spark will have the engine running hot so make sure your cooling system is appropriately modified.
    Last edited by Hib Halverson; 10-11-13 at 10:53 AM. Reason: added content

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    Quote Originally Posted by Hib Halverson View Post
    "Z Wiz" is right.

    An LS7 on 15 PSI is a potential disaster waiting to happen.

    There are two main reasons a supercharger, especially one with that much boost, is problematic on an LS7.

    1) The cylinder walls are too thin. That's the main reason GM did not use the LS7 case for the LS9
    2) The compression ratio is too high. To keep the engine out of detonation is going to require either a very retarded spark schedule or racing gasoline.

    The only way to make an LS7 with a Procharger durable for a reasonable amount of time is not drive it under high boost.

    No doubt, you're going to move ahead with this project regardless of our comments so, let me offer a few last suggestion:
    Make damn sure whomever you have calibrate the engine controls understands the potential detonation problem and knows how to address it. Start with 100-oct unleaded racing gas in the tank, then back down the octane to pump gas as the calibrator reworks the spark schedule. The retarded spark will have the engine running hot so make sure your cooling system is appropriately modified.
    I expected no less,so if its ok with your doctors i will post dyno numbers any way

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    When I lived in Phoenix, I knew a number of happy 427 Procharged C5 and C6 owners. As in all balls to the wall mods, you have to approach it carefully by managing both boost and tuning, and water injection doesn't hurt. But the others are right - without careful total engine management, engine failure can be almost instantaneous.
    There are times for thinking, and times for acting, but the art is in the balance


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    LS7 build done 6 Shooter's Avatar
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    Quote Originally Posted by catbert View Post
    When I lived in Phoenix, I knew a number of happy 427 Procharged C5 and C6 owners. As in all balls to the wall mods, you have to approach it carefully by managing both boost and tuning, and water injection doesn't hurt. But the others are right - without careful total engine management, engine failure can be almost instantaneous.
    Water-alcohol injection, provided the system is calibrated properly and the supply tank is big enough, would likely be a practical way to solve the detonation issue but you still have the problem with lots of boost, cylinder wall strength and head gasket sealing.

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    Quote Originally Posted by Hib Halverson View Post
    Water-alcohol injection, provided the system is calibrated properly and the supply tank is big enough, would likely be a practical way to solve the detonation issue but you still have the problem with lots of boost, cylinder wall strength and head gasket sealing.
    ...and that's what engine management parameters are all about. It does work, and the tool is a tuner who knows the limit of the system. I don't think anyone would expect an unbridled blown LSX to survive. I just checked with my friend in AZ - he has 27,000 street/strip miles on his C5 427. I don't expect he uses lots of boost too often, but it's there. I don't know what his boost is limited to. He won't say.
    There are times for thinking, and times for acting, but the art is in the balance


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    Guys,
    Let him have his fun!
    Just because my LS7 went BOOM on the Dyno does not mean his will.

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    Quote Originally Posted by toppthat View Post
    I expected no less,so if its ok with your doctors i will post dyno numbers any way
    Ah...let's see...the build was done two months ago and no numbers. Still waiting to see the chassis dyno results from the LS7 with 15-pounds boost.

    Also, I'm waiting to hear how Catbert's "tuner" can make the engine live on 15 psi.

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    Quote Originally Posted by Hib Halverson View Post
    Ah...let's see...the build was done two months ago and no numbers. Still waiting to see the chassis dyno results from the LS7 with 15-pounds boost.

    Also, I'm waiting to hear how Catbert's "tuner" can make the engine live on 15 psi.
    If you're referring to my rebuilt LS7 with a F1c at a stock pulley setting of 10lbs. No I have completed the break in,but have to wait until weather allows me to return to my builder to install Cry02 heads up software for blower and tune. Looking at rims and better traction for now.

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    Quote Originally Posted by toppthat View Post
    If you're referring to my rebuilt LS7 with a F1c at a stock pulley setting of 10lbs. No I have completed the break in,but have to wait until weather allows me to return to my builder to install Cry02 heads up software for blower and tune. Looking at rims and better traction for now.
    I guess I'm confused a bit. I could have sworn the OP in this thread said "starting at 15 pounds", but I've been wrong before.
    Whatever.

    When you had your LS7 rebuilt, what was done to the lower end?

    Did the engine builder run it on his dyno?

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    Quote Originally Posted by Hib Halverson View Post
    I guess I'm confused a bit. I could have sworn the OP in this thread said "starting at 15 pounds", but I've been wrong before.
    Whatever.

    When you had your LS7 rebuilt, what was done to the lower end?

    Did the engine builder run it on his dyno?
    My builder,Frank at Total Power started with mast heads,kooks headers,comp cam,fast 102,N.W102,and a vararam.It worked out great,so i told him to do whatever it takes to my LS7 to make it and the car itself safe for a larger procharger. Ross coated pistons calles ultra rods,magnum crank twin oil coolers,Cry02 intercooler chiller and a lot of machine shop work. Clutch driveshaft trans and halfshafts. Coilovers and swaybars about sum it up.Its broke in but the final tune has to be done before any hard driving. Im not new to all the hard luck LS7 stories. I wont get into the cost but if i wanted a LS9 or a E Force i would of got one. I love the new sound,and when its dynoed i will post results.

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