Cam lift question.

Discussion in 'High Performance Modifications' started by JoshHooper, Jun 26, 2013.

  1. JoshHooper

    JoshHooper Member

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    I dont really know much about the cam i put into my 355. What can I do to figure out what the lift is and stuff? I really wanna know how to figure out the lift because i am looking into a set of Vortec heads. Thanks!
     
  2. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Trying to figure valve lift? Simply multiply cam lift times rocker ratio. So if cam lift is .330 and rocker ratio is 1.5, valve lift will be .495. Just be aware that most cam manufacturers advertise lift with 1.5 rocker ratio.
     
  3. JoshHooper

    JoshHooper Member

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    thanks bud. I have done a little research and i kinda think my cam has a little over.500 lift. And Vortecs only support .450 lift, correct?
     
  4. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Vortec heads will support more lift if you notch the push rod holes.
     
  5. JoshHooper

    JoshHooper Member

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    How do you do that?
     
  6. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    The major problem is the retainers hitting the valve stem seals and guides. GM performance says .475" is the max on stock vortecs. The seller "AlexsParts" on ebay sells a spring and retainer kit that lets you run up to I think .550 lift on un modified vortec heads. Use a dial indicator on your rocker to get a rough idea of lift if your engine is assembled. Dial indicator on the lifter body would be more accurate if the intake is off. An engine I helped build for my friend is running a Comp 275 DEH .462/.482" lift cam on vortecs w/ Z28 springs w/ the inner damper removed. The retainers hit the valve stem seals at .510" on his heads when I checked it. I advised him that was close as hell but he decided to run it, and it has been running for several years w/ no problems. But that really reinforces that the .475" max spec really is it
     
    Last edited: Jun 27, 2013
  7. JoshHooper

    JoshHooper Member

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    Thank you. I really need a good set of heads haha
     
  8. AJ_72

    AJ_72 Veteran Member

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    For a Vortec alternative look into the Iron Eagles at Aerohead Racing .

    Chevy High Performance mag did a test of these heads and got pretty good numbers with them.


    Granted, it's a 383 IIRC, but it'll give you an idea of what they're capable of. They were nearly the same average HP and torque as the Vortec heads on the same engine even though they have a larger combustion chamber by 10cc's.

    Here's the full article.

    Cylinder Head Vital Specs - Power Curves

    BTW, they're not rebuilt. CHP made a mistake when printing that.
     
  9. grzewnicki

    grzewnicki Veteran Member Lifetime Gold Member

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    It will only run you between $75-$100 to get the valve guides cut down by a machine shop. You can also buy the tool to do it, but it costs almost as much.
     
  10. HyPer

    HyPer Veteran Member Lifetime Gold Member

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    The cheapest way to gain a little cushion room(either turn the secondary groove into the valve stems, or get 2 groove valves)is to remove the valve seals on the guides and run an O-ring and umbrella seal setup, like the older engines had before the days of emissions. The valve guides and valve stems will love you alot longer running the older setup too, as it increases lubrication for the guides and stems. The only reason they moved to seals, was to help pass cold start emissions.
     

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