1970 3927186 cylinder heads

Discussion in 'Original Drivetrain Topic' started by 2ndGenCrazy, Nov 3, 2017.

  1. 2ndGenCrazy

    2ndGenCrazy Veteran Member

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    I have a set of January 1970 date matched 2.02/1.60 186 heads I would like to sell. I am curious if the early date (for Z28) adds value, and what is the value? They were recently serviced by a machine shop, but I have not torn them down to inspect them. They have stock spring diameter, screw in studs and guide plates.
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    They should have good value for someone with an early Z28 who needs a set. Also, the LT1 Corvette used the same ones so somebody with a car like that might be interested too.
     
  3. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Early heads do tend to have more value as they appeal to a somewhat larger audience. You are going for the date code guys which like to stay within about 4 weeks from car build date for heads and blocks, so folks with a mid January build cars to early to mid February build cars, in my opinion. Those guys will be most interested. Otherwise, as a general group anyone with a 1970 Z28 or LT-1 Corvette who are not so date specific but who are at least looking for the right casting numbers and details (screw in studs and guide plates which can be easily added) will be interested. The '186 heads were also used on other applications like 350-350HP 'vettes (without guide plates, but with 2.02-1.60 valves) and 350-300HP (maybe others?) with 1.94-1.50 valves from 1969-1970 on any Chevy. I'm pretty sure that these particular heads were from the Flint Michigan plant which was the only plant that had the tooling to unshroud the 2.02 intake valve. Tonawanda also made these heads, but only with the 1.94 intakes.
    Someone please correct me if I am wrong on these details.
     
  4. l16pilot

    l16pilot Veteran Member Lifetime Gold Member

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    ^^ I think you pretty much nailed it, Dave.
     
  5. 2ndGenCrazy

    2ndGenCrazy Veteran Member

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    Upstate New York
    Great info Dave.

    A few years back, I did a mild resto on a "born with" 70Z.
    The heads were both cast F 27 0
    The block was F 23 0
    The engine stamp was V0701 CTC
    The build date was 07C, late week.
    Norwood car.

    I made an Excel sheet with as many dates as I could find on the car with the help of this site.

    The engines were also in Nova Yenko Dueces (168 total IIRC)
    as well as other COPO applications, probably Nova.
     
  6. Gary S

    Gary S Administrator Lifetime Gold Member

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    70lt1z28
    Your list appears essentially correct with the possible exception of the 350hp/350 L46 on the Corvette. Colvin lists that one as having the 3947041 heads. Also, with all the other applications such as the Z28, the Corvette LT1, and the Yenko Deuce there was a mix of 3927186 and 3947041 heads used. Also, on the 300hp engines with small valves, there was a mix of both castings used. These two castings are essentially the same.
    That doesn't take anything away from a good set of 186 heads as they were probably the most commonly used head for the Z28 and the LT1.
     
  7. COPO

    COPO Veteran Member Lifetime Gold Member

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    Make sure the heads were pressure tested too.
     
  8. 2ndGenCrazy

    2ndGenCrazy Veteran Member

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    Upstate New York
    They look very good, so I have decided to strip them down and have them cleaned and pressure tested. They appear to be original 202/160 heads, but no way to be sure.
    Were the heads cast at more than one foundry?
     
  9. 2ndGenCrazy

    2ndGenCrazy Veteran Member

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    Upstate New York
    I will be dropping the castings off for pressure test this week. I expect them to pass as there is no visible evidence of any coolant leakage in the most critical areas around the valve seats. The dates are A14, and A15 1970. Are there any suggestions for value if I decide to post them up in the for sale section? I am exploring shipping options as these weigh 45# each.
     
  10. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    To tell original 202/160' look to to see if the intake valve area in the combustion chamber has had a machining operation. This will remove the rough cast finish in this area of the combustion chamber. If it has been machined and the heads have not been previously rebuilt and the larger valves added (and unshrouded by the rebuilder), than it is a factory large valve head. As I said in an earlier post, only the Flint plant had the tooling to unshroud the large intake valves in the combustion chamber. While it isn't definitive, it is most likely then they were cast at Flint. Tonawanda was the other location that made these and while it is theoretically possible that between casting and machining they were moved from one plant to another, I sure can't see a good reason why this would happen.
    These heads also were used on the Corvette LT-1 and L-46, but in the latter with press in studs.
     

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