OWO head cross section pics

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  • #1

    OWO head cross section pics

    Sectioned a scrap OWO head to get a better idea what the ports look like. Pics:

    Intake


    Exhaust


    Exhaust short side zoom
  • #2
    Velly nice, cut through the guide too
  • #3
    This is nice, I've been meaning to start grinding on my VG33 heads.
    BLOZ UP.com
    It is not recommended to confirm proper installation by driving into walls or other barriers as this could cause personal injury or damage to the vehicle.
  • #4
    Need to do some similar cuts on a set of earlier heads so we can compare.
    Prius… because Pretentious wouldn't fit across the back of the car…

    Cheap, Fast, Reliable - pick any two

    My 1986 Turbo Build
  • #5
    jaqattack02;n769613 wrote: Need to do some similar cuts on a set of earlier heads so we can compare.
    I don't have any earlier V52, 21V or 85E heads to section. If someone wants to send me one, I can do it.
  • #6
    That would be cool, would be even better if someone could get the sections on a scanner.
    Prius… because Pretentious wouldn't fit across the back of the car…

    Cheap, Fast, Reliable - pick any two

    My 1986 Turbo Build
  • #7
    Pictures aren't loading over here. hmmm
    - VG30DET (HE341) 86 300ZX - 1982 280ZX Turbo - Headered NA 1986 300ZX 2+2 - 2000 Xterra -
  • #8
    Now, I've never ported heads before, but from what I understand the idea is to smooth flow as much as possible. That hard edge on the near side of the intake, and especially on the exhaust side, is it safe to smooth that whole transition out? Is there a reason why it should or shouldn't be touched?

    Build thread http://z31performance.com/showthread…-Paint-done-eh
  • #9
    Yea, a lot of what you're trying to do is the same as using mandrel bent exhaust piping, you don't want the gases to expand and contract at each bend, everytime you expand the cross sectional area, from the area before it, the gases lose velocity…

    For porting heads, there's another aspect to think about, and that is direction; you also want to shape the ports to turn the air to the ideal angle relative to the valve opening before arriving at the valve (intake side), which is why you see the near side hump
  • #10
    Mr. 510 has an interesting post on the nissan pathfinders forum about VG cylinder heads:

    There are two styles of VG heads, the early V52/21V casting and the later 85E/OWO casting. The 85E castings came out in mid '87 I think in Z31s. These are the heads of the "W series" VG30 that everybody wants due to their better intake port shape and cams. The OWO heads are found on all VG33 engines and are the same casting as the 85E but use the larger 10mm exhaust studs. This pic is a comparison of port molds of the early vs. late VG heads: One of the many good pics from the thread:
    [ATTACH=CONFIG]n770108[/ATTACH]

    You can see that in the early port the air rams into the far wall and has to make a 90 degree turn to flow past the valve into the cylinder. Not so good. The later heads are a HUGE improvement but left as-produced they do not flow any better because the exhaust ports are screwed up. There are big steps just above the valve seats that effectively reduce the diameter of the opening by about 3/16":
  • #11
    open up the top side of the exhaust ports, and youve got a real winner!
    Damn dirty angels....these cars!

    Current Daily Driver - 86 Turbo.
    Under the cover - THE BANANA… that needs to be re-energized.
    sigpic
  • #12
    How timely, I just flow tested some heads.

    I tested both heads on a SF600 bench, with a 3.3 sized cylinder bore at 28" of water.

    R-21v results

    Intake, average of all three ports.
    lift, flow
    .1, 57.33
    .2, 108.33
    .3, 144.66
    .4, 160.66
    .5, 163.66
    .6, 167.33

    Exhaust, Just one port
    lift, flow
    .1,43
    .2,86
    .3,97
    .4,99
    .5,100

    OWO results

    Intake, one port
    lift, flow
    .1,58
    .2,112
    .3,140
    .4,164
    .5,178
    .6,176

    Exhaust, one port
    lift, flow
    .1,39
    .2,89
    .3,112
    .4,114
    .5,115
    .6,115
  • #13
    Did you perchance flow at 0.05" increments?
    BLOZ UP.com
    It is not recommended to confirm proper installation by driving into walls or other barriers as this could cause personal injury or damage to the vehicle.
  • #14
    Made spreadsheet: https://docs.google.com/spreadsheet/ccc?key=0ArzU_jZP3kl4dGNySVdFVXBnTkJGWkFacGNQbGxOb 2c&usp=sharing
    BLOZ UP.com
    It is not recommended to confirm proper installation by driving into walls or other barriers as this could cause personal injury or damage to the vehicle.
  • #15
    I now have access to a SF600 flow bench so I will be flowing several different heads.
    I will start flowing every .050, and stop at .450, no use in going any higher, there really aren't any cams with that high lift to worry much over .450.

    We did a back cut on a set of stock valves and re-flowed both heads, the difference was negligible.

    I also flowed both heads with some minor porting, cleaned up the SSR, unshrouding, ect., they only picked up flow above .400" lift, so it really wouldn't help much in the real world.

    I working now on testing with the +1mm Ferra valves. We have to get the right tooling to open up the throat, and do a good valve job. They normally work with engines that have 2.5" valves so they don't have any small tooling.
    I also plan on testing with a 30deg. seat angle. The 30deg. seat is supposed to help with low lift flow, and with these engines that's all we have.
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