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  • #1

    engine build

    Ok so some of you might know from my threads that I have the LT4 top end. The intake is in my shop and the heads are on the way. The car right now has 1 5/8 JBA headers, CAI and 1.6 RR. I have other stuff but not motor related. Anyway, what do you motor gurus suggest or what would you do if the goal was 450-500 rwhp? Will ported/polished intake/heads and a cam do it? Do I need a 383, 396 to get there as well? Would you got to four bolt main? Just remeber it has to be NA.

    Thanks,

    Jorge
    97 TA, M6, JBA ceramic coated headers, Borla Cat-back exhaust, 1.6 RR, 160 Thermo, LT4 knock sensor, CAI, Bils, Hotchkis all around, GT rotors, B&M shifter, Magnecor wires, Granatelli MAF
    In the shop LT4 Intake and heads.
    Tags: None
  • #2
    Just out of curiousity, is this motor supposed to pass CA smog?
    94 Black T/A GT, Advanced Induction 355, 3200 stall, built 4L60E, Moser 9", Baer Brakes, Shooting for 11s...

    Comment

    • #3
      What kind of trans you going to run? That will determine the flywheel HP you need to make to reach your goal of 500rwHP.

      4L60E: 500 / (1 - 0.83) = 602 flywheelHP
      T56: 500 / (1 - 0.875) = 571 flywheelHP
      TH400: 500 / (1 - 0.79) = 633 flywheelHP

      Need to narrow it down a little more. You will definitely need some 300cfm heads, and a fairly big (I'd guess 240/246 .600+/.600+ or even bigger) cam. I don't know if you're going to make it with the LT4 castings. You might be looking at a set of really big AFR's. If you're never going with a power adder, definitely go for a 396. Probably looking at close to 12:1 on CR. Marginal on pump gas, unless you keep the DCR low with a narrow LSA (~108-110) on the cam. If you're running an automatic, its going to need a high stall convertor, and at least 3.73 gears.

      Then you need a decent exhaust system. The JBA 1-5/8" headers will strangle a 600+ HP 396. They were very poor performers on my bolt-on stocker.

      Injectors will be approaching 50#/HR, and you need a much bigger pump to support them. That drives you into an external driver for the low impedance injectors, since the stock PCM can't handle anything over a 42#/HR high impedance injector. At that HP level you might want to consider an aftermarket ECU. Definitely need a 58mm TB or a Monoblade.

      My approach was to build an "emissions legal", mild street engine, with nitrous in two stages, 125HP for the street, and another 150HP for the track. With a relatively mild 10.8:1, 381ci, 230/242 114LSA 0.590/0.590 solid roller, and LT4 heads flowing approx 290cfm, I made 500 flywheel HP and 435rwHP through a T56. Push the button for the 1st stage of nitrous and it made over 550rwHP. Add the second stage and it made 670rwHP, but there was no way you could use that kind of power on the street with street tire.

      You're looking to make as much as 100-130HP more than that. Going to take some good parts.
      Fred

      381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor

      Comment

      • #4
        Originally posted by soCalTA
        Ok so some of you might know from my threads that I have the LT4 top end. The intake is in my shop and the heads are on the way. The car right now has 1 5/8 JBA headers, CAI and 1.6 RR. I have other stuff but not motor related. Anyway, what do you motor gurus suggest or what would you do if the goal was 450-500 rwhp? Will ported/polished intake/heads and a cam do it? Do I need a 383, 396 to get there as well? Would you got to four bolt main? Just remeber it has to be NA.

        Thanks,

        Jorge
        I have the LT4 top end, but its ported a bit. Im in the 450-500 rwhp range, but on a hundred shot of nitrous. The stroker set up adds a lot more torque.....over 550-600 ft/lbs to the wheels (which is what makes a street car "feel" fast.) Its defininately a little cheaper and easier to get there with a little help. I kind of like having the power there only when I want it......I find that my N/A motor is enough power to easily overpower my street tires (nittos) up into 3rd gear.....and if im at the track with slicks I can add the power at the touch of a button. Doing it N/A will take some $$$ and a lot of work....and then the streetability of the motor may be questionable. It has definately been done before though....
        96 WS6 Formula: Ram Air, 383 Stroker, Ported LT4 Heads and Manifold, 1.6 Crane Rollers, 58MM T.B., AS&M Headers, Borla Exhaust, Meziere Elec. H2O Pump, Canton Deep Sump Oil Pan, 100 HP OF TNT N2O!! , T56 Conversion w/ Pro 5.0 shifter, SPEC Stage 3 Clutch, Hotchkiss Subframe Conn., Lakewood Adj. Panhard Bar, Spohn Adj. LCA's, BMR Adj. T.A., Custom 12 bolt w/ 3:73's, Moser Axles, Eaton Posi, Moser Girdle
        11.6 @ 123mph (1.6 60' - getting there )

        Comment

        • #5
          OK looks like I need to add a few more things. The car has to pass CA smog, the car is an M6, needs to be streetable since she is going to be my daily driver and no Nitrous and maybe a supercharger. I would really like to keep it normally aspirated. Keep in mind this is just a fact finding mission here so if can't happen then it can't happen.
          97 TA, M6, JBA ceramic coated headers, Borla Cat-back exhaust, 1.6 RR, 160 Thermo, LT4 knock sensor, CAI, Bils, Hotchkis all around, GT rotors, B&M shifter, Magnecor wires, Granatelli MAF
          In the shop LT4 Intake and heads.

          Comment

          • #6
            500 RWHP is definately obtainable through LT4 heads, but it takes some work and some finess.

            First of all you are going to need some quality parts on the bottom end. Forged crank, forged rods, and forged aluminum pistons. I would definately recommend getting your block converted to a 4 bolt splayed main. You are going to need to have your main bores CNC line honed. You are going to want to run a quality bearing such as the Clevite's. I'd also recommend that you have the cylinder bores done with a CNC as well, and then torque plate honed at minimum.

            You need to have the rotating assembly balanced very well. This will be critical in dictating bearing life and freeing up some power as well. It will be critcal as well to run quality valvetrain componenets.

            You will need to run a 2.00" intake valve and a 1.60" exhaust valve. You are most likely going to be spinning the motor to at least 6600 to obtain 500 RWHP, so titanium valvetrain components would be a good idea. Another item that would help your valvetrain to live longer and free up some power would be to run a belt driven timing set. Jesel and Comp make a pretty neat adjustable belt drive that will fir the LT1/4. You can get to 500 RWHP with a hydraulic cam but it is going to have to be fairly big. Something over 242/246 duration and over .600 of lift" and a LSA most likely 112 or under like Fred pointed out. Another obvious option would be to run a solid roller setup. This would make the 500 RWHP much easier to get to. This would require solid lifters, a solid roller cam, springs for a solid cam, and at least chrome-moly pushrods.

            The stock PCM can handle larger than a 42 lb/hr injector with an impedance converter, but I wouldn't recommend it. I was making 488 RWHP through my LT4 383 motor with a 42 lb/hr injector. I never saw the injector go over 82% duty cycle so it was fine. I was also running a belt driven vacuum pump. This vacuum pump gave me 16 RWHP on the dyno. You are going to need a good adjustable fuel pressure regulator and obviously a good supporting pump.

            You are going to need your LT4 heads to flow at least 305cfm @ .600" of lift. This is usually right around a stage 3 port. LT4 heads can be worked to flow around 320 but this is where the finess factor comes in.

            I'd recommend using a 1 7/8 LT header. At the 500 RWHP mark, a 1 3/4 will be slightly restrictive on a 383, 396, or 409. A stepped header will give you even a few more ponies.

            It's going to boil down to how much time and $$$ you are willing to part with.

            Comment

            • #7
              Thank you Kevin ... great answer and some very interesting things I will need to think about.
              97 TA, M6, JBA ceramic coated headers, Borla Cat-back exhaust, 1.6 RR, 160 Thermo, LT4 knock sensor, CAI, Bils, Hotchkis all around, GT rotors, B&M shifter, Magnecor wires, Granatelli MAF
              In the shop LT4 Intake and heads.

              Comment

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