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Thread: Sniper loud whistle/hiss normal?

  1. #1

    Default Sniper loud whistle/hiss normal? SOLVED!

    Hey all. Got it running pretty well, and I'll have more questions on fine tuning. But for now, it has a pretty loud whistle from the TBI at about 3/4 throttle? It's just at one particular throttle setting, and I just want to rule out a vacuum leak or some other nonsense. Is this normal? Thanks.

    EDIT: No more whistle! As per a few people's recommendation, I added a spacer between the TBI and intake manifold. It needs to be a 4 hole spacer, not open, and people have reported good results with a 1/4 thick gasket. I went with a 1/2" phenolic spacer and it completely eliminated the loud noise.
    Last edited by BrianSanDiego; 08-28-2017 at 03:44 PM.

  2. #2
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    This is usually a vacuum leak or the IAC valve. You might want to try a little more IAC Hold Position.
    If the idle speed screw/IAC Position relationship is correct (see below) this shouldn't be a problem.
    If you'd like to eliminate the IAC valve as a possibility, temporarily block off the IAC air inlet port with a piece of tape.
    Quote Originally Posted by Holley Sniper EFI Quick Start Manual
    IDLE SETTING/THROTTLE PLATE SETTING
    Once the engine is up to operating temperature, the idle speed can be set to what was configured in the Wizard.
    To do this, open up the Initial Startup gauge screen that was used in section 17.0. With the vehicle in neutral,
    adjust the idle screw until the IAC Position reads between 2 and 10%. While adjusting the screw if the TPS
    Position reads begins to read higher than 0% cycling the ignition switch will recalibrate the TPS back to zero.
    NOTE: Do not attempt to set the target idle speed and IAC position until the engine is above 160°F!
    http://documents.holley.com/199r11193.pdf (Holley Sniper EFI Quick Start Manual - "Idle Setting/Throttle Plate Setting", Page 12)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

    Default

    Yes, it's much louder than the IAC. Loud whistle almost like a blow-off valve. I thought it was part of the Sniper EFI design, glad I asked! Thanks for the info, I'll troubleshoot & report back. B.

  4. #4

    Default

    Did you ever resolve this problem? I added links of mine.
    https://youtu.be/18CED4mljO0
    https://youtu.be/d4QSOQG3cjE
    Last edited by Micribs; 04-21-2017 at 09:26 PM. Reason: Add link for videos

  5. #5

    Default

    Nope, still have a loud whistle. I checked for vacuum leaks, unplugged the PCV, etc. and its still there. As loud as it is its hard to imagine everyone doesn't have the same noise, but I guess not. If it's not "normal", all I can think of is that that it might be somehow be caused by the way the TBI mounts to my older multiple bolt hole Edelbrock manifold. I plan on swapping that out eventually, partially because of the whistle. We'll see! B.
    EDIT: Micribs, that's what mine sounds like too. Really conspicuous when I'm driving too.

  6. #6

    Default

    My car runs fine and I'm glad you noticed it in video. I called Holley Tech and they said it was gasket between manifold & Sniper. I changed it with a thicker Fel-Pro one, because they said the thin stock one in the kit would act like a blade of grass between your fingers when you blow on it and whistle. Which made sense so I made sure there was no gasket hanging over the edge when I replaced it, and it still didn't change. My motor is a 396" Big Block Chevy with a Edelbrock Air-Gap intake. If you cover throttle body with you hand the whistle goes away.

  7. #7
    Join Date
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    Determine if this is happening due to a manifold base gasket issue or the IAC valve. If you'd like to eliminate the IAC valve as a possibility, temporarily block off the IAC air inlet port with a piece of tape.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  8. #8

    Default

    Danny, is that the triangular port towards the back of Sniper? If so, I covered that with my fingers and the car started to die? Unfortunately, I'm laid up because I just had a knee replacement and will be a couple weeks before I'm back out in the garage.

  9. #9
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    Quote Originally Posted by Micribs View Post
    Danny, is that the triangular port towards the back of Sniper?
    Yes, the triangular air inlet port between the two secondary throttle bores.

    If so, I covered that with my fingers and the car started to die?
    But did it stop the loud whistle?

    Unfortunately, I'm laid up because I just had a knee replacement and will be a couple weeks before I'm back out in the garage.
    Sorry to read that, I hope you recover quickly.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  10. #10

    Default

    Thanks for replies Danny. As soon as I can get back out there, I will check & follow up.

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