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  1. #1

    Default After market heads

    Is there any advantage to using after market cylinder heads. Is the cost worth it or is it best to stay with the original factory setup?

  2. #2


    What year and what are you trying to do with the car?

  3. #3


    A general question. The consensus seems to be that the stock heads are already well engineered with the later dog leg style even more so. When I read the Edelbrock data it indicates (as an example) a combustion chamber volume of 56cc, intake runner volume of 185 cc and an exhaust of 70 cc. What do these numbers mean and how do they compare to the stock specification? I also noticed that exhaust valve diameters are slightly smaller than the factory specification. What bearing would this have. Looking for reliable reliable streetable power in the 450 to 500 HP range

  4. #4


    I was asking what year for the same reason - oval port vs. dogleg. I'd go with the consensus as the dogleg heads flow really well, oval port not so much.

    The stock combustion chamber volume for the doglegs is 58cc (stock oval port is 51cc). So 56cc would give a slight increase in compression ratio from the 58cc heads. As an example going from 51cc heads to 58cc heads equates to a .6 drop in compression, i.e. 10.2:1 down to 9.6:1 (larger volume = less compression). There's a formula for it but I don't have it in front of me.

    I don't know the stock intake/exhaust runner volume so I can't compare the two. Valve size can affect air velocity but that is also a question I can't answer with specifics.

    In my opinion, if you were looking to upgrade oval port heads with the Edelbrock heads then you've got a big enough difference in performance to make it worthwhile. Realistically, I think it's going to be tough to get reliable, streetable power in the 450-500 hp range though 'reliable' and 'streetable' could be subjective. However, 400 hp is doable in an engine that isn't too temperamental.

  5. #5


    Thanks again for your answers. I have a buddy that works in an engine reman shop, I'm itching to get him an AMC motor to build (it would his first). Yes 350 to 400 HP is more practical, after all the cars are very light.

  6. #6


    You're welcome. If you haven't already you might want to look at this thread
    There may be some ideas in there that you'll find useful.

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