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Thread: Turbo Engine Recipe?

  1. #1
    Can anyone give me a good recipe for a Twin Turbo 350 chevy. I melted #6 piston and am ready to rebuild. Would like to compare ideas before I get into it.
    Spec's on current engine are as follows:
    Heads are new World Products 67cc heads (standard
    small valve versions with as measured 69cc combustion
    chambers - chambers were close to 70cc when received
    but I had to slightly mill them in order to true them
    up and then I equalized the chambers @ 69cc). Valve
    seats were multi-angled cut, and valves were "back
    cut" and radiused/polished for increased flow. Valve
    bowls were "ported/radiused". Valve size is 1.94"
    intakes and 1.5" exhausts. Total calculated
    compression ratio is 8.05:1. This is using head vol.
    of 69cc, deck hgt. of +.008" (total quench hgt. is
    .047" - .045" is considered minimum perfect for turbo
    engines), gasket vol. of 9cc (Fel-Pro #1014 .039"
    thick head gaskets), TRW forged pistons #L2441F with a
    as measured dish vol. of -23.5cc (suppose to be
    -21.1cc dish but measured -23.5cc). Bore is 4.030"
    diameter and stroke is stock 3.48" = 355cid.
    Rings are Childs & Albert Moly High Strength Plasma
    coated (dutile iron) with wider 1st & 2nd ring end
    gaps for turbo usage (.019" gap).
    Complete engine rotating assembly was balanced.
    Exhaust manifold gaskets are Fel-Pro with steel core.
    Cam is Crane Energizer #10003 (204 deg. duration @
    .050" tappet lift & with .427" valve lift. and 110
    deg. lobe separation). Cam is normally installed
    straight up with 5 deg. advance built in. This cam is
    retarded via 8 deg. offset bushing in cam timing chain
    sprocket for a total retard of 3 deg. (5 deg. advanced
    -8 deg. bushing = 3 deg. retard). Timing chain is a
    Cloyes Tru-Roller.
    Rockers are 1.52:1 Competition Cams roller tip
    Ignition timing is 8 deg. initial advance with an
    additional 24 degrees in the dist., all in by 2800 RPM
    (max. advance is 32 degrees total). Initial timing
    can be reduced to 6 deg. initial, but recommend not
    going below that. Contrary to popular belief,
    retarded timing (for long durations) does reduce
    knock, but then it increases combustion chamber temps.
    as well which then causes knock to return with a
    Note my thinking when building up this engine
    initially was to increase low end torque (for better
    hole shot), and use the turbo's to increase top end.
    I know that I overdid this on the low end and this
    caused the top end to suffer somewhat, and I told you
    about retarding the cam (8 degree retard bushing) to
    get back some of the top end. The new cam was the
    next step (according to my discussions with the
    experts- Gale Banks & Engle Cams), but I never
    installed it. It depends upon how you are going to
    use the boat (everything is a compromise). If you are
    going to ski, tube, etc. and bottom end is more
    important, then return the cam timing back to it's
    initial setting of 5 deg. advanced (replace the cam
    sprocket offset bushing with a "zero" bushing). If
    top end speed and high speed cruising is where it will
    be operated at, then leave it as is, or replace the
    cam with the new one (your choice either way).
    Frankly, as it is, I think it is a good compromise
    with great performance in all catagories (but we
    always want more).
    New Engle cam spec is as follows:
    #1002H (grind # TCS-2HYD). Duration @ .050" tappet
    lift is 216 deg. intake & 210 deg. exhaust. Valve
    lift is .458" intake & .440" exhaust. Lobe center is
    116 deg. Description per Engle: Turbocharger Hyd.
    Camshaft designed for modified engines with 8:1
    compression ratio. Power band 2800 to 6000 RPM. This
    cam will definately be weaker on the bottom end, but
    would wake up the top end considerably!
    [ August 17, 2002, 06:30 AM: Message edited by: Rayhill ]

  2. #2
    Jungle Boy
    I don't know if this will help or not, but last year when we were racing in New Zealand, there are many NZ'ers that were running turbo set ups on their jet boats. If you could hook up with a few of them guys, they may be able to advise you on what is working for them. I know that some of their boats were working real good and they had very few failures during the 600 KM race. There is a link to NZ boating on

  3. #3
    What fuel system are you running?are you running water injection or intercoolers? where on #6 piston did it fry ? intake or exhaust ?

  4. #4
    What fuel system are you running? Mechanical Holley Fuel Pump, Factory Intake, Quad-jet carb.
    are you running water injection or intercoolers?
    Neither. I have a brand new water injection system the previous owner opted not to use ???
    where on #6 piston did it fry ? intake or exhaust ? exhaust

  5. #5
    if you want the best advice call carson brumet/ brumet marine in pasadena he is the best turbo guy in so cal as far as i'm concerened

  6. #6
    I would run the water injection or intercoolers, sounds like you have a lean effect going on.twin turbos can run very lean if your carb is not jetted right. could I see any pictures of #6 piston, it would help me out in understanding what happened.

  7. #7
    Thanks all
    Been gone all week
    Here are a couple a pics.
    I dont have a pic of the piston yet.
    When I bought this boat I was very sceptical about having twin turbos. Reliability ????
    I figured the first sign of trouble and the turbos must go. But they are way too much fun!
    I want a dependable package if there is one?
    Thanks again
    [img]!9VTCRjjQ924jez4HOCmou0r8OrAyOfwk9XOBIpH m41jF7PyOyvM5K6Jhf2cNilRgEsxoxUjOnkyPbiXDGWcI1G2*d cVRTqKOo/CV-23ENGINESIDE.jpg[/img]

  8. #8
    Another pic!
    [img] pDj6XMVthtMdZA8kRPrzzbC6TLN7kXtFCyqnN!u*BUXdIQDaQB uAC4AcAA/CV-23ENGINE.jpg[/img]

  9. #9
    Thats an old M&W gear setup. I used to run one similer to yours on a 460 Ford. Is your fuel pump boost referenced to the air box? It could be the engine is leaning out from dropping fuel press. How much boost are you running? It is possible for the carb metering to go south when you get above 9-10 lbs and make sure you have the diffuser plate at the air inlet of the pressure box.

  10. #10
    The fuel pressure is referenced to the air box.
    Running 5-6 lbs. of boost.
    What kind of intake, carb., and fuel pump did you use on your 460 set up.
    What do you think of the M&W set up ????

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