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Thread: tune a holley carb

  1. #1

    Default tune a holley carb

    I run a Chevy 355ci all old school in an 85 Trans Am with stock th700r4 tranny and stock converter. I'm getting now 25l/100kms in city driving being very gentle. I wanna try to tune the Holley 750 4160 vacuum secondaries. I have on this engine to get a better gas mileage so here is what I was thinking to do if you could tell me if that would help or be worse etc...: Thanks.

    -Move the distributor vacuum advance from ported to manifold vacuum (should I then back the distributor to avoid to much advance?
    -Put a 50 power-valve as my car idles in gear (TH700R4 tranny) at 10'.
    -Put a spring in the vacuum secondaries housing that opens at the highest rpm (maybe the black spring).
    -Put a wire in the IFR (Idle feed restrictors) to limit the opening.
    -Leave the 67 actual main jets (70 originals).
    -Tune then the carb with a vacuum gauge to get the highest RPM.

  2. #2
    Join Date
    Dec 2009


    Absolutely connect the vacuum advance canister to full manifold vacuum.
    25°-30° of initial timing (idle) is perfectly acceptable, especially for bigger camshafts.

    8°-12° of additional vacuum advance is the typical limit (some canisters are adjustable).
    The timed spark port (on metering block) is only for stock emissions/EGR engines.
    A stiffer secondary spring may just cause you to step down further on the accelerator pedal and consume more fuel anyway.

    Wire inserted in idle feed restriction:

    1. To discharge nozzle from accelerator pump
    2. To main air bleed
    3. To main discharge nozzle
    4. To Idle air bleed
    5. Used with auxiliary air bleed
    6. Not used (not drilled)
    7. Dowel for metering block
    8. To curb idle transfer slot
    9. To curb idle discharge

    10. To timed spark port
    11. Fuel bowl vent
    12. To main air bleed
    13. To main discharge nozzle
    14. To Idle air bleed
    15. Dowel for metering block
    16. Used with auxiliary air bleed
    17. To curb idle transfer slot
    18. To curb idle discharge

    1. Accelerator pump discharge
    2. Main air bleed from main body
    3. Main passage to discharge nozzle
    4. Idle air bleed from main body
    5. Air bleed to main well
    6. Main body dowel
    7. Main air well
    8. Idle feed restriction from main well
    9. Idle fuel from main well
    10. Idle transfer to main body to curb idle adjusting screw
    11. Curb idle discharge
    12. Power valve channel restriction

    13. Fuel bowl vent
    14. Main air bleed from main body
    15. Main passage to discharge nozzle
    16. Idle air bleed from main body
    17. Air bleed to main well
    18. Timed spark passage
    19. Main body dowel
    20. Idle feed restriction from main well
    21. Idle fuel from main well
    22. Idle transfer to main body to curb idle adjusting screw
    23. Curb idle discharge
    24. Power valve channel restriction
    Last edited by Danny Cabral; 06-05-2010 at 05:48 AM.
    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/2800 RPM converter, M4602G aluminum driveshaft, FRPP 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 tires.

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