Vortec Cylinder Heads: The Definitive Guide

Discussion in 'Engine Topic' started by MikeM79, Jul 4, 2006.

  1. larrylarry

    larrylarry Veteran Member

    1,313
    41
    Dec 22, 2011
    San Antonio Tx
    I worry about gas mileage in my DD, my 78 Z28 I don’t even think about it, it’s for burning it up as fast it can.
    I’d replace the bearings and rings and move up to roller lifters and cam. I’m using a roller cam that gives more torque & HP at a lower rpm, reaches its peak at 5 grand instead of 6 grand & above like most performances cams.
     
  2. djorgensen3

    djorgensen3 Veteran Member

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    6
    Oct 15, 2009
    Peoria, Az
    If you're sure you will end up at 10:1, I would absolutely put the vortecs on. You can run 91 or 93 octane and will likely be fine and you will appreciate the extra performance. And you won't have to change the cam unless you just want to.
     
  3. TheMadDoctor

    TheMadDoctor New Member

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    Apr 21, 2010
    Orlando, Fl
    My 79 is my daily driver, that's why I worry about mileage. Thank you for your responses, the heads I was looking at do have the steam holes drilled already, but the more I think about it, it seems like I will have too much compression for pump gas.
     
  4. djorgensen3

    djorgensen3 Veteran Member

    276
    6
    Oct 15, 2009
    Peoria, Az
    I ran 10.5:1 compression on a 350 here in Phoenix in the summers on pump gas and 64cc doublehump heads with no issues. And those heads weren't as good as the vortecs. Use the vortecs...
     
  5. larrylarry

    larrylarry Veteran Member

    1,313
    41
    Dec 22, 2011
    San Antonio Tx
    You would have to know how far down the pistons are in the cylinders or are they flat tops then how much dish the pistons have or how much the valve relieve is on a flat top piston. Then the compressed thickness of the head gasket you’ll be using & the chamber size of the heads then use a compression calculator. This will give you an idea of how much you have for compression. IMO 9.5 - 10 is about all you’d want for a DD.
     
  6. TheMadDoctor

    TheMadDoctor New Member

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    Apr 21, 2010
    Orlando, Fl
    I just looked around on the web, and the best reference I found came from the NHRA saying that my 73 400 had 19.5 dished pistons. I am assuming that this is a stock block, as that's what the guy I bought it from said, and I'll take my oil pressure as evidence to the fact. That being said, I reworked my compression in the calculator on the summit website, with a .03 MLS gasket, I would only be at 9.6:1 compression. That being said, I have no chance of arriving at a good quench number, unless I mill the block, but I'm pretty sure that the dished pistons don't do anything to help quench anyways. Should I be worried about quench on a DD? I know my current setup doesn't help it.
     

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