492 vs 186 Heads

Discussion in 'High Performance Modifications' started by airarbiter1, Dec 16, 2004.

  1. airarbiter1

    airarbiter1 Member

    90
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    Jul 16, 2002
    New Windsor,MD Baltimore
    Does anybody know for sure how much more hp the angle plug #492 GM heads make over the #186 heads with 2.02/1.60? Is it just the angle plug or do the heads have a different port designs that flows better?
     
  2. rustbucket79

    rustbucket79 Veteran Member

    Other than a slight difference in casting or machining tolerences, they will create similar power. The angle plug is supposed to be beneficial when running dome pistons, but from a visual standpoint shifting the electrode 1/4" or so towards the exhaust valve doesn't look like it would make any difference (that is strictly an opinion, with ZERO fact supporting or dismissing it)
    Neither of those heads will have flame hardened exhaust seats and will require lead additive for running unleaded fuel.

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    Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
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  3. airarbiter1

    airarbiter1 Member

    90
    0
    Jul 16, 2002
    New Windsor,MD Baltimore
    So a set of Dart Iron Eagles either 180cc or 195cc heads would be a BIG improvement over either of the GM heads?
     
  4. PONYEATER

    PONYEATER Veteran Member Lifetime Gold Member

    2,796
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    Nov 2, 1999
    Arlington, WA
    any new aftermarket head will out perform a older gm head.(there are exceptions so don't flame me)
    For the simple improvements of combustion chamber design help with a better flame front.


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    Arron Spitzer
    1979 Camaro "not Stock"
    Tech/ Sales
    Randy's Ring & Pinion
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  5. Marv D

    Marv D Veteran Member Lifetime Gold Member

    In brute flow numbers yes, but without the cam and compression to take advantage of the increased flow of the Iron Eagles, you would be shooting yourself in the foot on a street motor. Huge flow numbers tends to make for soggy low end torque numbers.

    I don't know how much I agree with rust on the angle plugs, being there is so much rumor, mystery and theory associated with the angle plug design. It's become a 'standard' in upper end performance heads so there must be something to it, but I would welcome any solid proof as to 'why'. Relocating the plug slightly to place it more in the incoming stream of the cool intake charge should help cool the plug. You can 'theoritically' run a slightly hotter plug. (a consideration only when your running a cold racing plug in a high compression, high HP motor) And the plugs should run cleaner and last longer without fouling. Should also help in keeping the cylinder from loading up and fouling at low rpms against the transbrake etc. But again,, I think this is all theory and can't remember even where I heard it. I can only assume GM and the aftermarket head manufacturers have proved on a dyno that the angle plug design has merit, or we'd see straight plug in the upper end comp heads. In a motor where burn rates happen in milliseconds at 6,7 or 9grand,,, I wonder how they really determined that putting the spark kernel 'over here' was better than 'over there'.

    As far as 492 vs 186 castings. The 186 is a slightly lighter casting (less than 1 pound as I remember), both are 64cc and all the info I have says both flow in the 208-215 range as-cast with 2.02 intakes. Probably of more importance is the angle plug location with small tube headers brings headaches in headers available for the 2nd Gen. Camaro, Do a search and you'll find PLENTY of post about angle plug heads and finding a plug that keeps the wires away from the headers. If you already have the headers, bolt them up against the angle plug heads with plugs and wires and see how well you fit. That alone may make the decision for you. There ARE headers (usually the 1-3/4") that will work, but it's worth checking out before you bolt all the pieces together in the chassis.
     
  6. hhott71

    hhott71 Veteran Member Lifetime Gold Member

    14,377
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    Mar 30, 2001
    Joplin Mo. 64801
    Canfields, afrs or Pro/Topline would be a big improvement over the darts
     
  7. Mwilson

    Mwilson Veteran Member

    Im runnin 186's I love them but i woulda trashed'um if i had known that i would have this much money in 35 yr old technology!
    If they are free use'em if your gonna pay for them by some pro topline's!

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    1972 Camaro 350 factory heads 1.94/1.5 street driven full interior
    93 octane everything works 7.59
    89.54 mph
    Never owned a trailer never will!
     
  8. Mike-78 Z-28

    Mike-78 Z-28 Veteran Member

    1,904
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    Mar 4, 2003
    ElDorado Arkansas
    The "Smoke" said anything over a 12-1 piston in a 350 starts to build a wall of fuel around the plug due to the dome which is why they moved the plug.

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    1978 Z-28 purchased new by me -$6750
    Click here to view present state photo
    Look above for glory days.
    1994 Formula
    1982 350 S-10
     
  9. rustbucket79

    rustbucket79 Veteran Member

    "Relocating the plug slightly to place it more in the incoming stream of the cool intake charge should help cool the plug. You can 'theoritically' run a slightly hotter plug."

    Uh Marv, the plugs are aimed towards the exhaust valves, but you already knew that. [​IMG]
    That was supposed to be a benefit, since the mixture nearest the hot exhaust valve would be better atomized. I Agree there must be a benefit since all the high end heads run them, and I as well would like the proper answer.
    One other thing, the factory heads had a much lower plug location than most aftermarket heads making them poorer in a dome piston application compared to an aftermarket higher plug located head.

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    Custom Auto, your source for quality machine work, cores and new parts at competetive pricing right here in British Columbia 1-888-563-4050
    A Canadian, EH? (with a 10 second street car)
     
  10. pdq67

    pdq67 BANNED

    10,496
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    Jul 26, 2001
    Columbia, MO, USA
    I wonder how well a set of the 50 cc chambered, 200 cc port heads that Powerhouse sells would perform on a flat-top piston motor that is high compressioned and combinationed to take advantage of them???

    pdq67
     

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