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Thread: Best practices - dual throttle bodies on a Tunnel Ram?

  1. #1

    Default Best practices - dual throttle bodies on a Tunnel Ram?

    I'm wanting to install a Holley HP EFI System on a 440 Chrysler with individual injectors in welded bungs. I want to run dual dry throttle bodies on a Tunnel Ram. Can I use 2 of the Universal 4BBL 1000 CFM 4150 flange throttle bodies, part# 112-588? I know there will be dual TPS & IAC. Could I leave the second TPS in place and put a block off plate on the second throttle body's IAC? Are there throttle bodies that would be a better choice? Would this cause any tuning issues? What pitfalls am I not seeing? Thank you.

  2. #2
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    Quote Originally Posted by nordyneken View Post
    I know there will be dual TPS & IAC. Could I leave the second TPS in place...
    Yes, use only one TPS and one IAC motor. The Holley ECU can run two IAC motors, but only one is required.

    ...and put a block off plate on the second throttle body's IAC?
    It can't be a simple block-off plate; that would leaves the IAC passage wide open.
    It must a block-off plate with a spring loaded pintle, such as this from Accufab: LINK.

    Are there throttle bodies that would be a better choice? Would this cause any tuning issues?
    If this isn't a high flowing, high RPM, race oriented engine build, 2000 CFM might be too much (poor port airflow velocity).
    http://vmaxmotorsports.com/?p=241 (Additional Information)
    https://forums.holley.com/showthread...6144#post76144 (Related Forum Post)
    You may also want to consider using progressive secondary linkage type throttle bodies, to ease off idle/low RPM response.
    https://forums.holley.com/showthread...4591#post54591 (Related Forum Post)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  3. #3

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    The other potential issue I see, is that the throttle bodies may leak enough air to render the IAC ineffective at achieving desired idle speed. Andrew

  4. #4

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    You probably won't need the IAC. You might have to run the idle a little rich (13.3-13.5 or so), but it's no big deal. I've got a 60's era Enderle stack manifold with no IAC, and it runs fine. I'd run both throttle bodies simultaneously, just be sure they're synced.
    Last edited by 3 window; 02-10-2016 at 01:29 PM. Reason: Correction

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    Quote Originally Posted by andrewb70 View Post
    The other potential issue I see, is that the throttle bodies may leak enough air to render the IAC ineffective at achieving desired idle speed.
    That shouldn't be a problem, because the dual throttle bodies will will be adjusted to inhale the same idle airflow, as a single throttle body. If not, the engine would idle higher. Also, the throttle blades are closed far enough to achieve an IAC position of around 2%, so it has plenty of range. If both the throttle bodies actually leaked too much air to idle reasonably, that's another problem.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  6. #6

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    Quote Originally Posted by Danny Cabral View Post
    ....If both the throttle bodies actually leaked too much air to idle reasonably, that's another problem.
    Unfortunately, I have seen this problem creep up. Even my dual OEM DBW throttle bodies leak enough, that my IAC ultimately degenerates to zero, and I have fiddled with it a lot. Andrew

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    Quote Originally Posted by andrewb70 View Post
    Unfortunately, I have seen this problem creep up. Even my dual OEM DBW throttle bodies leak enough, that my IAC ultimately degenerates to zero, and I have fiddled with it a lot.
    Maybe we're referring to two different scenarios. If the air leak is happening slowly, over time, then the idle speed screw is backing off (which is common). Initially, if a reasonable idle speed can't be achieved, even with the throttle blades fully closed, then there's too much leakage (which is what I thought you were referring to).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  8. #8

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    Quote Originally Posted by Danny Cabral View Post
    ...Initially, if a reasonable idle speed can't be achieved, even with the throttle blades fully closed, then there's too much leakage (which is what I thought you were referring to).
    This is what I'm referring to. I see Holley has some relatively new die cast throttle bodies. I bet those are better than what I experienced 10 years ago, with billet throttle bodies. Andrew

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    Quote Originally Posted by andrewb70 View Post
    Unfortunately, I have seen this problem creep up.
    ...that my IAC ultimately degenerates to zero.
    OK, I understand. Your above comments are what confused me.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  10. #10

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    I'm not afraid to admit when I've eaten a little crow. I was able to adjust my throttle bodies to the point where I get 5% IAC, and the desired RPM that I'm looking for (975 RPM). Andrew

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