882 to 186 heads. Any gains?

Discussion in '1970 - 1973 Specific' started by Bob1970sbc, Feb 22, 2018.

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  1. Bob1970sbc

    Bob1970sbc New Member

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    Feb 22, 2018
    Switching out my 882 heads for a set of 186. Will I see a difference
     
  2. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Ringgold, GA
    You're going from a 76cc combustion chamber to a 64cc. That can produce both positive (more compression) and negative (more pinging) effects. What's the rest of the engine combo? I'm guessing this is not a 1970 LT1 engine?

    BTW - welcome to NastyZ. :)
     
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  3. Bob1970sbc

    Bob1970sbc New Member

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    Feb 22, 2018
    Also going to replace the 2.73 open with a eaton style posi. Considering 3.08, 3.36, or 3.55. Th 350 tran. Tires 26" tall. Thoughts?
     
  4. Bob1970sbc

    Bob1970sbc New Member

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    Feb 22, 2018
    Haven't broke in it yet. I figure stock 350
     
  5. Bob1970sbc

    Bob1970sbc New Member

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    Feb 22, 2018
  6. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Ringgold, GA
    You'll see some gain in power with the increased compression ratio, which may require premium fuel. I wouldn't guess at a number. Are both the same valve size?

    Have the heads been checked by a machine shop for cracks, warped deck, etc? With these heads getting close to 50 years old, a lot can be wrong.
     
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  7. Gary S

    Gary S Administrator Lifetime Gold Member

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    Bismarck, North Dakota
    On a 70 Z28 engine with domed pistons, the 186 head gave 11:1 compression. On the 70SS engine with flat top pistons, the 186 head gave 10.25:1 compression. If you have dished pistons common on later engines, the compression will be lower than either of the above combos and with decent gas, should be a very streetable compression ratio.
     
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  8. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

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    San Jose, CA, USA
    Neither set of heads are particularly good. Going from the 72cc to 64cc combustion chamber will bump compression from factory 8.5-1 up to ~9.6-1 that's good for more power, but will also push you into the land of 91 Octane fuel.
    Gears are really going to depend on what you're doing with the car.
     
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  9. Bob1970sbc

    Bob1970sbc New Member

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    Feb 22, 2018
    I've had the car for ten years or so. Bought it off a preacher who said the Motor was recently rebuilt and bored 30 over. Mild "RV" cam. 1406 edelbrock performer intake. I've added a good HEI. Full headers and exhaust. Cars just a weekend driver nice weather car. Just want a little more pop on the street. Not a drag car. I would guess the pistons are flat topped or dished. The heads look in good shape. No porting. New springs and look to be the smaller valves pressed in studs shaved or plained on combustion side. Look ready to install. Got them from a guy that works at a machine shop
     
  10. Bob1970sbc

    Bob1970sbc New Member

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    Feb 22, 2018
    Date codes on the heads are February 24th and 17th 1969. I figured they may have been married to an engine at the factory. I did some trading to get them and would say I got about 300 dollars in them. I also wondered if they might be worth more to the 69 z28 guys. I see big numbers on e bay but they seem unrealistic. If I got a profit from them I could put that towards better heads
     
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