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Are these decent small block heads?

Discussion in 'The Garage' started by Midwestblue, Nov 18, 2004.

  1. Midwestblue

    Midwestblue Registered Member

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    HEAD CASTING #'S

    Here are all the casting numbers, and what I think they were used on. Would these be good heads to use for a 9 to 1 compression, fairly mild motor, around 300-325 horsepower?
    GM 11

    3973487...used on 71-72 350 LT1, 75cc chamber
     
  2. bluebomber

    bluebomber Newbie

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    those are pretty good heads i think 75cc chambers port volume is good too. for a whole listing of chevy castings numbers go to www.thedirtforum.com and find the tool box it has a list of a bunch with specs
     
  3. POWERMAD

    POWERMAD 1/2 ton status

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    Location:
    Oregon
    I have a set of those in the shed.
    This is what I came up with them.

    1971 Z28 Engine - LT1 330hp (gross, 275hp NET) Casting # GM P/N Description
    Block 3970010 4 bolt main, suffix codes: CGP, CGR
    Crankshaft 330550 Forged steel
    Heads 3973487 75.47 cc, 2.02/1.6 valves, screw in studs & guide plates
    Cam 3972182 3972178 symbol: (1) square Solid lifter - 0.458(I)/0.484(E) lift, 317I/346E duration
    Pistons Flat w/valve relief - yields 9.0:1 compression
    Intake 3959594
    Carb (A/T) 3989022 Holley List 4800, 780cfm , 4150 series - 4BBL
    Carb (M/T) 3989021 Holley List 4801, 780cfm , 4150 series - 4BBL
    LH Exhaust 3989041 Rear exit, log type w/AIR, 2.026 outlet
    RH Exhaust 3986330 Rear exit, log type w/AIR, 1.96 outlet
    Distributor 1112049 Manual Trans, RFI, single point w/vacuum
    Distributor 1112074 Auto Trans, RFI, single point w/vacuum
    Alternator: Delcotron 37 Amp, part # 1100837
    Water Pump: 3957170

    Cylinder head has swirl polished valves and chrome valve stems.
    Alternate cylinder head was 3986316 (unverified).

    It seems it was a decent head back in the day.
     

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