Rec port intake on Oval port heads?

Discussion in 'Competition Camaros' started by Bigdog, Nov 12, 2009.

  1. Bigdog

    Bigdog Veteran Member Lifetime Gold Member

    1,223
    0
    Jun 30, 2006
    Lake Jackson, Tx.
    I have a chance to pick up a Victor intake that is fully plumbed with a fogger system for a steal, but it is a Rect port intake and my heads are the GMPP 502 heads which are oval port.

    I have read where guys have used a Rec intake on an oval port head with no issues before but could not find any of those article in a search now that I need verification...

    Have any of you done this, or are doing it now or is it something I should just stay completely away from?

    Thanks.
     
  2. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member


    .

    I know and heard about dozens of guys doing oval intake on square port heads.
    Nobody I know has had good luck, doing it your way.
    It might work on a very mild type combo, but I would definitely not even think about it using a fogger.
    You don't want stuff bouncing and banging all over the place in there.

    If you really really just have to get this one. You can always epoxy the runners.
    The picture shows my heads with the corners ovaled out and some epoxy added.
    If it's that cheap, maybe you can buy and resell for a quick buck or two???
    Good luck.


    [​IMG]

    .
     
  3. Bigdog

    Bigdog Veteran Member Lifetime Gold Member

    1,223
    0
    Jun 30, 2006
    Lake Jackson, Tx.
    Thanks John.
    For the money I'd need to put back into it to make it right I think I will just wait and either add a fogger onto the port matched intake I have now or go ahead and get a halo plate system that was my original plan anyway.
    Cost will end up being the same and it will be done correctly.
    This was just popped up on the radar this morning and seemed like a good deal at the time, if I had rect heads it might have been.
     
    Last edited: Nov 12, 2009
  4. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

    8,847
    0
    Dec 8, 2000
    Republic of Texas
    Dave,
    Don't even sweat it. The Rect port works fine on ovals. Just us a rect gasket.
     
  5. mrnitrous

    mrnitrous Veteran Member

    581
    0
    May 12, 2008
    Anaheim Ca
    I'm with mrdragster on this one 100% the intake charge will be hitting a wall... never good.
     
  6. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

    8,847
    0
    Dec 8, 2000
    Republic of Texas
    It's an old trick that actually works good despite what all the magazines and internet experts would tell you.

    Very few "port matched" heads and intakes are actually matched anyway... If they aren't doweled, there is no way to confirm the intake is sitting where the holes are lined up...

    I've BTDT on this one as well as many other guys who ran into the 9's.

    Maybe the "wall" helps keep the fuel atomized but in any case, it's nothing to sweat.

    Go look under some BBC powered Comp Eliminator guys hoods ;)
     
  7. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member


    .

    Comp guys are some pretty slick guys. They absolutely know what they're doing.
    They also do not use N2O unless you run A/PM, like my car.
    All I know is there is no way in heck, I'm shooting something at 1000 PSI,
    and something at 7 PSI and something being drawn in by vacuum into a runner
    and then have it run into big *** protrusions in the runner.
    I'm not an expert, but I do have a small understanding of suspension and atomization of fuel particles.
    You want it mixed up and high velocity. Super mixed up and getting slowed down by big chunks of metal in the way,
    is not going to fill a cylinder as full. I would much rather have the higher velocity.
    Which I've seen many many times when guys hog the heck out of their heads and actually lose power.

    I also know my stuff lines up pretty damn close. I use a smaller gasket and trim to the ports.
    I look down the runner and line it up before torquing down the intake. If there is any lip, it's extremely small.

    Oval intakes, on rec heads has been around forever. I've never done it, but guys swear it helps with driveablility.
    Rec intake on oval heads, I just don't see it helping, and definitely not with a fogger.

    I'm going to ask some guys that know way more than I do, their thoughts later.

    .
     
  8. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

    8,847
    0
    Dec 8, 2000
    Republic of Texas
    The OEM and many aftermarket intakes the oval design will not cover the rectangular ports, so you have a massive vacuum leak going that way.

    Some combos have used the aftermarket oval intakes on a rect head. This should be helpful with reversion but if it actually helps the power, then heads are simply too big and you are using the intake to keep velocity up.

    The rectangular port intake on oval heads give you some plenum volume.

    It's another case of people over-thinking things and worrying about port matching is a good example. It has ben proven to work in many cases even though there is a large mismatch, but obviously it isn't a real issue or there would be power loss and other side effects.

    One very good example of this working is Ed Bigleys low 10 second 468 with OEM ovals and Eddy RPM Air Gap in rect port version.
    I believe there are some other similar combos being run by the TC guys into the 9s. Maybe Bob Wests?

    It's just nothing to sweat even with N2O. N2O may be going in under pressure but it becomes gaseous and will flow right along with the rest of the air/fuel mixture into the mismatched port. :)

    I understand air column theory and all that, and how some think the air is being pushed into the intake and into the mismatch at the intake/head flange but in reality the engine is "sucking" air in (vacuum created by piston drawing atmospheric pressure air into a lower pressure cylinder) and in that case the mismatch is just a larger volume of air available at the port entry.
     
  9. Bigdog

    Bigdog Veteran Member Lifetime Gold Member

    1,223
    0
    Jun 30, 2006
    Lake Jackson, Tx.
    Good info from boh sides and definetly worth looking into.
    By the time I got back to the guy to even discuss it in more detail it was already gone.

    Back to the drawing board now.
    May just look into a plate system for now to get back into the comfort zone with Nitrous again.
     
  10. 1980RS

    1980RS Veteran Member

    1,512
    0
    Jun 17, 2006
    Boy I don't know, I am with mrdragster on this one. If you spray it and a cyl. or 2 goes lean that you might melt some parts. Without spray most likely be ok, Not worth the chance on spray IM0.
     

Share This Page