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Technical Flathead Porting: Soup to Nuts . . . Pictures, Details and Opinions

Discussion in 'Traditional Hot Rods' started by Bored&Stroked, Nov 22, 2009.

  1. Hi!
    Joined: Oct 4, 2006
    Posts: 731

    Hi!
    Member
    from SoCal

    How is this done? Im in a similar situation right now.
     
  2. Pete1
    Joined: Aug 23, 2004
    Posts: 2,073

    Pete1
    Member
    from Wa.

    Plug one hole in the pattern and redrill it.
     
  3. Jack Gifford
    Joined: Jan 24, 2012
    Posts: 15

    Jack Gifford
    Member
    from Phelps, NY

    "... Soup to nuts..."? Where are head chambers discussed- I may have missed it?

    I may have something to contribute (hint: think valve unshrouding).
     
  4. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Just contribute.

    Valve unshrouding is well documented in the modern flathead books. Generally, it is done on machines not available to the backyard builder...unlike porting.
     
  5. Jack Gifford
    Joined: Jan 24, 2012
    Posts: 15

    Jack Gifford
    Member
    from Phelps, NY

    I haven't read any "flathead books". I'm curious if it's now common practice to barrel-shape the chamber walls surrounding the valves? The point being, to maximize flow while minimizing loss of compression ratio.
     
  6. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Joe Abbin, who has probably done as much flow bench work as anyone on flatheads, now recommends a simple plunge cut above the intake with a radiused cutter - I don't have the dimensions handy.

    Not quite sure what you mean by 'barrel-shape' though.
     
  7. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Joe Abbin, who has probably done as much flow bench work as anyone on flatheads, now recommends a simple plunge cut above the intake with a radiused cutter - I don't have the dimensions handy.

    Not quite sure what you mean by 'barrel-shape' though.
     
  8. Jack Gifford
    Joined: Jan 24, 2012
    Posts: 15

    Jack Gifford
    Member
    from Phelps, NY

    Barrel-shaped is the most simple description. The objective being to give greater valve-head-to-wall clearance while the valve head is off the seat, than when seated. It can't be accomplished by a plunge cut straight down from the deck surface of the head; a dynamic boring head on a CNC mill is the elegant approach. When I built billet heads for one-lung alky engines (for modified garden tractor pulling) I used a normal offset-boring head on a manual mill, feeding the head laterally into the rotating radiused tool (both intake and exhaust). I never got the heads (w/blocks) onto a flowbench, but the customers had good results on the track.
     
  9. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Well, there is a bang for the buck perspective too. A plunge cut with a radiused cutter is going to be significantly cheaper than a CNC program...bear in mind, you're talking relatively small improvements in flow in only the upper RPM ranges. Not viable for street use, really...
     
  10. Kustom Dick
    Joined: Nov 8, 2009
    Posts: 169

    Kustom Dick
    Member
    from Finland

    What do you guys think about this sharp edge before intake valve seat (shown in picture between numbers 3 - 7)? My friend told me I should porting the short side of intake port just like this before the valve seat, not make it smooth and round. Air flow would be better in tight turn.

    [​IMG]
     
  11. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,350

    38FLATTIE
    Member
    from Colorado


    Air doesn't like tight turns! I'd try and 'straighten' it as much as possible.
     
  12. Kustom Dick
    Joined: Nov 8, 2009
    Posts: 169

    Kustom Dick
    Member
    from Finland

    I agree with you, but he justify it that sharp corner suck air flow to valve. He hear that from "cylinderhead expert"... And that pic was in internet too...
     
  13. Kustom Dick
    Joined: Nov 8, 2009
    Posts: 169

    Kustom Dick
    Member
    from Finland

    What you think about exhaust baffles, any proven benefit or is flow getting worse?


    [​IMG]
     
  14. Vergil
    Joined: Dec 10, 2005
    Posts: 785

    Vergil
    Member

    My understanding is, as the air/fuel passes through the port some of the fuel droplets will be moving against the surface of the 2, 3, 7 side, as the air moves over the sharp edge the fuel will be sticking and sliding on the surface and pool under the sharp edge making for large droplets which will be harder to atomize in the chamber for combustion.

    Vergil
     
  15. Pete1
    Joined: Aug 23, 2004
    Posts: 2,073

    Pete1
    Member
    from Wa.

    That didn't work for me.
     
  16. Vergil
    Joined: Dec 10, 2005
    Posts: 785

    Vergil
    Member


    Did the sharp edge help for you?? I like different experiences that worked for others.

    Vergil
     
  17. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,350

    38FLATTIE
    Member
    from Colorado

    I have a hard time believing a sharp edge will be beneficial, even if it were on the Internet, or CNN!

    I think what most here may be overlooking, is the fact that all this pretty, really cool looking porting ,may not be doing much good!

    Ask anyone who ports for a living, and has a flow bench.To a man, they almost all say what they thought worked before they had a flow bench, isn't what really worked! That's why I laugh when someone says they know how, "because they just do", or say they do it "by the seat of there pants"! Lol!

    I think we can all agree, knocking off the sharp edges, and 'straightening' out the corners, as much as possible, will be somewhat beneficial. IMHO, though, without putting it on a flow bench, to measure results, you'll never really know how much you COULD have improved the head, with the same amount of effort.
     
  18. Pete1
    Joined: Aug 23, 2004
    Posts: 2,073

    Pete1
    Member
    from Wa.

    No sharp edges.
     
  19. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Joe Abbin has spent quite a few hours on the flow bench with various mods. He's got some good data.
     
  20. Jack Gifford
    Joined: Jan 24, 2012
    Posts: 15

    Jack Gifford
    Member
    from Phelps, NY

    Why are we discussing a view of an OHV port in this thread about flathead breathing?
     
  21. Awesome thread!!!
     
  22. fenderless
    Joined: Mar 31, 2006
    Posts: 1,286

    fenderless
    Member
    from Norway

    Hey D

    If your gona use the the baffels, and they came with studs that are threaded all the way? Don't use them, as they will stretch very easy.
    Use stock studs or order a set of ARP ones.

    ..............................
    Taildragger&fenderless
     
  23. Kustom Dick
    Joined: Nov 8, 2009
    Posts: 169

    Kustom Dick
    Member
    from Finland

    I have ARP studs.
     
  24. BillWallace
    Joined: May 6, 2011
    Posts: 132

    BillWallace
    Member

    The problem with these ports isnt just the sharp radius but the angle of entry is very curved & there is not much that can change that. The biggest single gain in manufactured ports is in the pocket behind the valve. Reducing any sharp edge & straighten the port in that area.
     
  25. plan9
    Joined: Jun 3, 2003
    Posts: 4,065

    plan9
    Member

    Looks great!!

    i decided to leave the exhaust baffles out, not enough time to do it last year but i have no data to say its beneficial or not.
     
  26. knucklepower
    Joined: Jan 9, 2009
    Posts: 148

    knucklepower
    Member
    from .

    bump, and save it for me:D, will do the same
    thanks for the good info
     
  27. Flat32
    Joined: Sep 14, 2005
    Posts: 27

    Flat32
    Member

    Ode to Flatdog, I miss him and think of him almost daily. When our coupes were running in the fifteens, mine mid and his low he lamented his quest to get into the fourteens was frustrating and chose to go supercharged. At that time he challenged me saying if I could show him a 14.999 or lower timeslip he'd take the blower off his '34 and continue his quest N/A.

    I set my goal at 14.5 and got it, but not before he checked out.

    I concentrated my efforts on chamber shape and continue to tweak it. Latest rendition pictured here.

    http://i646.photobucket.com/albums/uu187/Flat32/CHAMVOL_zpsb388c1c8.jpg

    Flat32
     
    nitro29 likes this.
  28. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,350

    38FLATTIE
    Member
    from Colorado

    Flat32, that's a real interesting shape! I'd sure like to see a side shot, to more fully understand the shape.

    I'd sure be interested in talking to you-I'd like to try that chamber design on my blown flathead, and compare the results!
     
  29. Model A Mark
    Joined: Apr 30, 2008
    Posts: 1,273

    Model A Mark
    Member
    from dallas
    1. Holley 94 Group

    yes please flat32, will you exsplane the chamber shape.
    thanks
     
  30. Flat32
    Joined: Sep 14, 2005
    Posts: 27

    Flat32
    Member

    Open where the air wants and needs to go, closed where it doesn't to keep CR high, 10-1 on my engine, and angled to enhance rotation (swirl) into the cylinder. Side of chamber opposite exhaust side is cut deeper, closer to the stud, and beyond the gasket line, yellow in the picture.

    Intake is shrouded at back and when open has little clearance over the top.

    Exhaust flow may seem somewhat blocked off at the cylinder, but Flatdog flow tests on exhaust showed flow out of the chamber tends to go sideways from the intake side and it makes sense that the flow is influenced by the exhaust port flow direction past the valve.

    Picture is a tweaked version of what's on my engine now. Good enough to get me a 13.822 timeslip, but needs the tweak to get targeted 13.5.

    Flat32
     

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