Vortec Cylinder Heads: The Definitive Guide

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

  1. BlackDog82

    BlackDog82 Veteran Member

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    I once bracket-raced against a guy who had a 400" SBC in a late-'70's Firebird, that ran 12-flat with 4.11 gears:
    he shelled them on the starting-line one weekend, and I offered him a set of 3.42s from my '79 Z28 I had no-intention of using again (he had his-own set of 3.42s that he used instead ), and he ended-up running 12-flats again, at a slightly higher MPH with a lower trap-speed RPM.
     
  2. sschevellefan

    sschevellefan Veteran Member

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    My buddy is runnig a 406 and has 4.11`s and doesn`t seem to have any problems. I just wasn`t sure what gears would be best. I`m building a vortec 383 with flat tops, should be around 11:1. I`m going to home port the vortecs and gasket match them. i was looking at the summit racing version but I don`t think it will give me the right DCR to run on pump gas. According to the compressio calculator I use the crane cam that Dirt ran will do the job.
     
  3. Dirt Reynolds

    Dirt Reynolds Veteran Member Lifetime Gold Member

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    They might be just right for a 383 which could use a bit more RPM through the traps with it's smaller cubes. The reason the 4.10 gear was a bit much in my case is because the 413 is simply too large an engine for the Vortecs to feed at RPM's much over 6000 or so. But under 6000 RPM on a 400 -- Vortecs make for one heck of a fast street car! And - that is their stock in trade. :cool:

    BlackDog82 -- I figure my car would have worked similar to your post. Lesser rear gear would have allowed the engine to dwell a little longer at lower RPM where the engine made more torque.
     
  4. Dirt Reynolds

    Dirt Reynolds Veteran Member Lifetime Gold Member

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    There is no "problems" per se, with 4.10 gears and the 400. It's just that when running down the 1/4 mile track, at about the 1000' mark you can 'feel' that the engine is about done pulling at around 5800 RPM or so. So I figure either less rear gear or a taller tire to compensate would get the trap RPM down to where it needs to be (under 6000) and the car would run either slightly quicker or maybe the same times, but would stress the engine less running at a lower RPM.

    A bigger cylinder head of around 210-215cc intake runner volume and bigger valves would allow for more power higher up in the RPM band, but that wasn't my original intended purpose for that engine.

    But just running around on the street, the 4.10's are a real hoot. :bowtie:
     
  5. BlackDog82

    BlackDog82 Veteran Member

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    The racer and I had been discussing if his car would run as-well/better with less-gear before his problems, and decided that 3.73s would be best for him:
    when the rear end unhinged itself, his 3.42s, laying on the shelf, were thrown in as a stop-gap measure, and the car responded well.....

    in-fact, it was more-consistent than before with 4.11s, and we figured the few hundredths it gave-up to 60' made it less-liable to spin, and the motor obviously liked to grunt going down the track.
     
  6. sschevellefan

    sschevellefan Veteran Member

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    that might be his deal because he`s running 215cc pro 1 heads and a Isky 304 mega cam.
     
  7. derbyu02

    derbyu02 New Member

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    Ok, now i've got a set of Vortec 906's that someone installed 2.02/1.60's in , would these be a good choice for a mild 350 build? Aren't these heads suscepitble to cracking under high heat conditions? wouldn't the bigger valves make it more vulnerable to cracking?
     
  8. Dirt Reynolds

    Dirt Reynolds Veteran Member Lifetime Gold Member

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    As long as they pass a pressure test they should be fine.
     
  9. jsmart

    jsmart Veteran Member Gold Member

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    Engine Block

    Hey guys and girls,

    Round 2 of silly questions. Well this one is going to be easy for all of yall I assume. Either the block is trash or this is no big deal. I'm ready either way so let me know. Just finished after two weeks of soaking in WD-40 the teardown of my '73 block that was going to get Vortec heads and I found this!!!:eek:

    Is it the end of this block or can it be saved....again this is my first expierience with any of this so I have no idea. Before I take it to the machine shop hopefully one of you can tell me if it's fatal or not.:whine:

    Thanks!
     
    Last edited: Dec 28, 2007
  10. sschevellefan

    sschevellefan Veteran Member

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    Should be ok. Should have it magged though. The piston doesn`t ride on that part of the cylinder. Just have the machine shop radius it so it doesn`t crack.
     

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