Chasing my tail... running in circles!
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Chasing my tail... running in circles!

  1. #1
    Senior Member Sharkbit's Avatar
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    Default Chasing my tail... running in circles!

    Just looking for some ideas here, been chasing this problem for close to 4 months. This has literally driven me nuts. Please help!

    Boat fires and idles perfect. Accelerates and cruises just great. When hammered it picks up pretty good then quits about 4800 and just kinda bangs...peters out. It just ain't right.

    19' Daytona jet berkeley pump A/B with all the goodies
    477 BBC 9.5-1 fresh only time on this thing was breaking in cam on test stand and maybe 5 hrs
    063 ovals mild port work
    Duration @ .050 241/249 .572/.590 LSA/ICL: 110/106 hydraulic flat
    single plane
    850 dp

    I have tried:
    replaced all power grounds, cables and switches.
    3 ignition setups, MSD and HEI (including running hot wire straight to battery) wires, plugs...
    3 carbs from running engines with similar setups
    used gas can straight to holley blue to carbs pressure never moves off 7 and bowls are staying full
    adjusted valves 2 different methods EOIC and TDC tried from zero to zero plus 1/2
    had valve springs tested
    pulled engine and degreed cam
    resealed intake
    shut off all water to headers

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  3. #2
    gn7
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    Quote Originally Posted by Sharkbit View Post
    Just looking for some ideas here, been chasing this problem for close to 4 months. This has literally driven me nuts. Please help!

    Boat fires and idles perfect. Accelerates and cruises just great. When hammered it picks up pretty good then quits about 4800 and just kinda bangs...peters out. It just ain't right.
    When you say "bangs" do you mean it actually backfires, or is that just a word you are using to describe it stops pulling?



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    steelcomp was here
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    Who's cam, lifters and springs? What are the spring specs?
    Same question as GN7...
    If God is your co-pilot, change seats!
    Acts 2:38, the perfect answer to the perfect question.

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  6. #4
    Senior Member Sharkbit's Avatar
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    It doesn't actually backfire or pop more a stuttering... kinda seems like a soft touch. But I tried a stock HEI and it does the same thing. The springs tested at 140lbs at the installed height.

    Here is a link to the cam Voodoo Hyd Cam Kit - Chevrolet Big Block 284/292 - Lunati Power
    Last edited by Sharkbit; 06-21-2013 at 05:17 PM.

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    Senior Member bp298's Avatar
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    Quote Originally Posted by Sharkbit View Post
    It doesn't actually backfire or pop more a stuttering... kinda seems like a soft touch. But I tried a stock HEI and it does the same thing. The springs tested at 140lbs at the installed height.

    Here is a link to the cam Voodoo Hyd Cam Kit - Chevrolet Big Block 284/292 - Lunati Power
    with nothing else to go on, on the trailer i'd disconnect the drive shaft, hook up the water and run it. put the timing light on it from idle to 5000. see if timing does something funny at elevated rpm.

  8. #6
    steelcomp was here
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    Quote Originally Posted by Sharkbit View Post
    It doesn't actually backfire or pop more a stuttering... kinda seems like a soft touch. But I tried a stock HEI and it does the same thing. The springs tested at 140lbs at the installed height.

    Here is a link to the cam Voodoo Hyd Cam Kit - Chevrolet Big Block 284/292 - Lunati Power
    Like bp said...check timing at rpm, but I'm also wondering about valve springs and valve train. That's a fairly agressive lobe for a HFT.
    If God is your co-pilot, change seats!
    Acts 2:38, the perfect answer to the perfect question.

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    Senior Member Sharkbit's Avatar
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    I have checked the timing all the way to max. It seems to like about 37 total the best.

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    Senior Member Sharkbit's Avatar
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    When I adjust the valves there are 2 that I can set the preload by hand. The plunger is super soft. Is that normal?

  11. #9
    gn7
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    Quote Originally Posted by steelcomp View Post
    Like bp said...check timing at rpm, but I'm also wondering about valve springs and valve train. That's a fairly agressive lobe for a HFT.
    No more aggressive than a Isky mega 292, I ran roughly the same seat pressure. I'm wondering if the lifters are up to the spring and the cam profile.



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  12. #10
    Senior Member Sharkbit's Avatar
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    I'm going to throw a set of lifters in it today. Any other thoughts?

  13. #11
    Senior Member MACHINEHEAD1's Avatar
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    A new set of lifters on a old cam? Not a good idea. Will run for just enough time to ID the problem (if its a lifter problem) before the cam takes a dump. 140 on the seat sounds right, and is enough to destroy the cam with a new set of lifters. You may get lucky, I wouldnt have that kind of luck!

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    Have you checked the fuel supply to see if it is getting enough fuel at the higher rpm? Sorry I missed your line about the fuel pressure.
    Last edited by VD Cruiser; 06-23-2013 at 05:29 AM.

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    Run a mechanical pump and see what happens. I had a same issue, turned out to be vapor lock due to vents. Fuel etc stayed just wouldn't flow .

  16. #14
    gn7
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    Quote Originally Posted by Sharkbit View Post
    I'm going to throw a set of lifters in it today. Any other thoughts?
    I don't think I'd try that. could turn out badly.
    You don't mention anything about fuel pressure, or anything about the fuel system, I.E. type pump, line size, fuel filter. Tank vents in the caps? Fuel tanks with fuel outlet on top with dip tubes?
    Like VD Cruiser posted, it could be a fuel delievery issue.

    You say the engine is new. You run this boat before with a different engine?



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