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Product Summary

External Ignition Box Required, HEI / Male Cap Type

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    Key Specs

    MFG. Part #8547
    BrandMSD
    Cap TypeHEI / Male
    Advance TypeMechanical
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    MSD 8547 Details

    If you have a slightly taller block or have decked the heads, the distance between the distributor mounting pad and the cam gear/oil pump drive may be different. MSD offers these Distributor with an adjustable slip collar with 1.5 of adjustment so you can be sure the distributor is installed correctly. The distributor shares the same features of the standard Pro-Billet Chevrolet model including a ball bearing guide, long sintered lower bushing and an oil seal. To trigger the MSD Ignition a maintenance-free magnetic pick-up is secured in the billet base of the distributor. Just above this pick-up assembly is an adjustable mechanical advance assembly.
    • Extra tall housing is designed for use with Alan Root, Donovan, Merlin and Rocket racing blocks
    • CNC machined billet aluminum housing and Dupont Rynite base
    • Adjustable slip collar mounting flange provides up to 3 of adjustment
    • Maintenance-free magnetic pickup and precision reluctor create stable trigger signals throughout the rpm range
    • Polished steel shaft is QPQ coated and guided by a sealed ball bearing and long sintered bushing
    • Advance plate and weights are fine blanked from chrome moly steel and QPQ coated for friction reduction
    • Mechanical advance assembly can be locked out for crank trigger systems
    • Advance weight pins are staked and tig welded to the plate
    • Nylon pads ensure smooth operation of the advance weights
    • Special oil tract improves lubrication to the distributor and cam gear
    • O-ring seals can be added to modified blocks to improve oil pressure control
    • Supplied with an HEI style distributor cap and rotor (accepts Cap-A-Dapts)
    • Must be used with an MSD Ignition Control
    • No CARB Exemption Order Number
    • Must be used with an MSD 6, 7, 8 or 10 Series Ignition.
    • Designed for racing blocks with maximum increased deck height such as Alan Root, Merlin and Rocket Blocks.
    • Extra tall slip collar provides nearly 3 inches of adjustment.

    Charts

    Rebates

    Holley Fuel Up Spring Savings Event 2026

    Save 10% instantly on select products across the Holley family of performance brands during the annual Holley Fuel Up Spring Savings Event 2026. Instant rebate period runs from March 30, 2026 through April 19, 2026.

    CARB Warning

    For race/ off road use or for use on pre-1966 vehicles.

    Emissions warning: this part only legal for sale or use in California for racing (competition) vehicles which may never be used, registered, or licensed for use upon a public highway, or if installed in vehicles model-year 1965 or older; motorcycles model-year 1977 or older; or off-highway recreational vehicles (such as off-road motorcycles and all-terrain vehicles) model-year 1996 and older. Any other use renders the vehicle tampered and not legal for use on California public highways (any public street or roadway, public dirt road, public park, or publicly maintained right of way open to the use of the public for vehicular travel). Violations subject to $37,500 penalty per violation per vehicle, revocation of registration, loss of use on California public right of ways, and proof of correction for tampering. There are similar restrictions and penalties under federal law and the laws of all other states with penalties under federal law of up to approximately $45,268 per tampered vehicle and/or engine.

    MSD 8547 Specifications

    KEY SPECS
    MFG. Part #8547
    BrandMSD
    Cap TypeHEI / Male
    Advance TypeMechanical
    GENERAL
    External Ignition Box RequiredYes
    Cap Terminal StyleHEI / Male
    Trigger StyleMagnetic
    Hall EffectNo
    Sync SignalNo
    Trigger SensorsSingle
    Gear MaterialIron
    Gear RotationStandard
    Ignition Box RequiredYes
    Mechanical Tach DriveNo
    Slip CollarYes
    Housing MaterialBillet Aluminum
    Housing FinishNatural
    Marine UseNo
    Sold in QuantityEach
    GTIN Code085132085477
    Customer Impersonation Script