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Oval port heads and rect port intake?

Discussion in 'The Hokey Ass Message Board' started by flattyAndy, Nov 27, 2013.

  1. flattyAndy
    Joined: Jun 2, 2008
    Posts: 8


    I'm sure it's been done but have any of you guys had it work out and actually run ok? I have a bitchin tunnel ram I want to run but can't afford new heads

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  2. bobby_Socks
    Joined: Apr 12, 2006
    Posts: 938

    from ǑǃƕǑ

    Yes. The rectangular port intake can be run on oval port heads, have not done the tunnel ram but have used other intakes with single four barrel. Just remember not to over carb...
  3. michev
    Joined: Aug 22, 2010
    Posts: 96


    I've done it running a rectangular port Dart intake on my oval port heads. The engine would RPM about 600 higher over a Holley Strip Dominator intake.
  4. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,779

    from Oregon

    Have a friend who's using a rectangle port tunnel ram on oval port 454, and it doesn't run well. If it's a good buy, I'd get the tunnel ram and either resell for profit, or try to trade for an oval port tunnel ram. I'm running an oval port Weiand on Edelbrock oval port heads with twin 600 vac. sec. Holleys, and it works so nice!

  5. robyyo
    Joined: Sep 8, 2005
    Posts: 236

    from Orange CA

    I don't think you should run a rectangular port on an oval port.
  6. Harell Los Angeles
    Joined: Dec 26, 2001
    Posts: 151

    Harell Los Angeles

    I've seen it where guys make the oval heads into pseudo rectangles by port matching them to the rectangle gaskets. Then let them quickly transition back to the oval port. Then it doesn't have a big weird non matching stop as it passes to the head.. Anyway that's one option.

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  7. M224SPEED
    Joined: May 12, 2010
    Posts: 171

    from Missouri

    Ran an L-88 square port intake on oval port heads for years,and never missed a beat,make sure you are using square port intake gaskets.
  8. I talked to Jeff Smith at Car Craft about this a while back. They had done some testing and in the 600HP range it didn't make a lot of difference.
    You have to remember that when the column of air is moving through the manifold and ports, the outer edge is fairly calm while the center is where the velocity is. At higher RPM it could cause some issues but you will probably run out of port size before it is a problem.
  9. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    from BC

    Well there you go. Couldn't be that he cant tune worth a shit.:rolleyes:
    Running a square port intake on oval port heads works well. Throw the square port intake on a flow bench, and map the port opening with the pitot tube, and the reason why will become clear.:rolleyes:
  10. saltflats
    Joined: Aug 14, 2007
    Posts: 10,744

    from Missouri

    I have some buddys that have done it with single 4 carb and clame to have been there best runnig street engins.
  11. hotrodarchaeologist
    Joined: Dec 4, 2007
    Posts: 501

    from Maine

    I ran a square port, single four intake on oval port heads on the BB 402 in my '57 Chevy. I just used what I had available at the time. It ran very well and would pull the front wheels off the ground running on the tuning problems...
  12. 1971BB427
    Joined: Mar 6, 2010
    Posts: 6,779

    from Oregon

    I don't think you can compare one intake with another. The differences in port shape on a hi rise, or lower intake, and the same differences on a tunnel ram with twin carbs are not equal. As well as a hi rise might work, tunnel rams don't seem to work as well with mismatched ports.
    Likewise for blower engines. Putting a square port blower intake on an oval port head will give all sorts of fits. I got my oval port heads this way. The original owner tried to put a square port blower intake on them, and never could get it to run right, nor could several good tuners. They finally swapped to rectangle port heads, and I bought the oval ports cheap.
  13. chevy57dude
    Joined: Dec 10, 2007
    Posts: 6,323


    With the amount of parts available these days, running mismatched intake / heads is a variable that could just well be eliminated. Everyone's combo is different, so someone else's setup could work fine but in no way indicates what would happen on your car with the parts you own. How about selling the rect. tunnel ram and picking up one that matches your heads? The Edelbrock Street tunnel ram I run is around $400 new and about 1/2 that on the used market. No, this doesn't address the OP question. But you could buy/sell/swap and end up with a matched combo for $200 or less.
    Joined: Nov 10, 2005
    Posts: 846

    from Holly

    Old time Super Stock drag cars used rec port intakes on oval port heads regularly.
    Last edited: Nov 29, 2013
  15. Lytles Garage
    Joined: May 6, 2011
    Posts: 621

    Lytles Garage

    Have had a sq. port tunnel ram on oval port heads for 13 years now on my model A pickup, many many miles ,works fine ! Chris
  16. ardyboy
    Joined: Mar 5, 2008
    Posts: 664


    Fel Pro has a couple of intake gaskets that they recommend for this application
  17. indyjps
    Joined: Feb 21, 2007
    Posts: 4,164


    Just epoxy the runners in the intake and port match them to the heads, I don't know the epoxy's name but have run several sets of heads that were epoxied to maximize flow on a flowbench.
  18. indyjps
    Joined: Feb 21, 2007
    Posts: 4,164


  19. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    from BC

  20. hdman6465
    Joined: Jul 5, 2009
    Posts: 654


    This has worked fine on my car for 29 yrs. Do you think I should change it now? I didn't know there was a problem till the experts chimed in!
  21. black 62
    Joined: Jul 12, 2012
    Posts: 1,895

    black 62
    from arkansas

    careful ---you are going to expose the whole "port match myth"...
  22. You bastards, now you got me rethinking a square port intake I seen !
  23. fab32
    Joined: May 14, 2002
    Posts: 13,985

    Member Emeritus

    Back in 1966 (late 1965 actually) a friend and I both bought '66 SS 396 Chevelles with 360 hp 396s (just prior to the release of the 375 hp version). For a very short period of time the Chevrolet parts book listed the 425 hp/427 rectangular port aluminum intake at the same price as the cast iron oval port intake. When we were informed about this oversight both of us ordered the rectangular intake...........cost us less than $40 each. Both cars initially used the single feed Holley that came on the 340 hp engines and both ran really good with a slight jetting change. I eventually put a 780 Holley (stock carb for the 375/425 HP 396/427) and it added 2-3 hundred rpm to the power peak.

  24. johnybsic
    Joined: Oct 8, 2009
    Posts: 612

    from las vegas

    People have done it Give it a shot. Intake gaskets are cheap enough. I was gonna do it with a big block cross-ram I have, But i didn't have a second carb so i just sent with a regular single carb oval port intake.
    Mothballed the cross ram, One day!

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