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Convert overhead to a flathead?

Discussion in 'The Hokey Ass Message Board' started by tommorookian, Sep 26, 2012.

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  1. I see lots of conversions of flatheads to overheads. Has anyone EVER found a way to convert an overhead into a flathead? A nice modern short block would make a good base for a flathead that would look good in any hotrod. Bigest problem would seem to be room in the block for the valve heads?

    I know, I know, I'm NUTS! Just tired of waiting for shadow rods aluminum flatty.
  2. Morgan91
    Joined: Sep 12, 2010
    Posts: 560

    from Australia

    I'm with you fuzzy
  3. It's something that popped into my head when looking at an all aluminium Rover/Buick 215 short block. Light, strong and easily available over here. Well - nothing's impossible given enough money, time and skill. The big problem with any OHV engine that I can think of is that there is no place for exhaust ports.

  4. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope

    I suppose you could cast up a new block that used all new innards from say a SBC or something, and some new heads,then engineer some valve train stuff. The cam on a flathead needs gobs more lift since there are no rockers to add 1.6 ratio.
    The big Q is, "WHY?"........
  5. propwash
    Joined: Jul 25, 2005
    Posts: 3,857

    from Las Vegas

    ya can do it - ya just need unlimited financial resources and a couple of good engineers on the payroll. You also need a decent foundry to manufacture the cylinder heads, machine shop to finish 'em off and when you're done, you'll own the most expensive mild horsepower engine around. Everybody will want to be YOU
  6. X2 on the WHY????
  7. I'm on it......
    Just as soon as I finish converting my hydraulic brakes to cable actuated manual brakes....
  8. Midget25
    Joined: May 2, 2012
    Posts: 168


    I bet right now you are wishing you didn't posted this.
  9. oldandkrusty
    Joined: Oct 8, 2002
    Posts: 2,141


    This is a question that I must admit had never occured to me. However, thinking about it, the major stumbling block has to be the block itself, pun intended! In a flathead the valves and springs and valve seats are all carried within the block itself whereas in an OHV all of those things are carried within the removeable heads. As far as I can see, converting from an OHV to a FH mandates that a new block be cast up and machined to accept the valves. Of course, new heads would also need to be cast and machined. I hate to say it, but this is an question that really never needed to be asked.
  10. Lytles Garage
    Joined: May 6, 2011
    Posts: 621

    Lytles Garage

    "Its better to be thought a fool, than open your mouth, and remove ALL doubt" I HATE FLATHEADS !!!
  11. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,625

    Rusty O'Toole

    You may have something. Not making an actual flathead out of an OHV but making valve covers that mimic the look of a flathead. Valve covers shaped like a finned aluminum head.

    Like those valve covers to make your Chev look like a 52 Olds.

    The first guy to do it would be a genius. The last 1000 would be douchebags.
    Last edited: Sep 26, 2012
  12. Piece of cake, cast a flat head with bungs for direct injection and poppet valves for exhaust. I am all over that, we should be able to drop the HP and torque by at least 60%.
  13. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,681

    Bruce Lancaster
    Member Emeritus

    Damn fool project! Go get the drawing board!
    Ain't no place to PUT the valves. Start with a very compact block, then, probably 215 or maybe a 302 Ford because of ridiculously short deck height and too short rods.
    Add complex casting atop block containing ports (we better put them all out the top like a Caddy, anything else puts us an order of magnitude further into insanity) and putting the valve pockets right over the tappets, probably with a bit of cant for better flow. Bore all the way through and add in cylinder sleeves long enough to go through cylinder portion of our new piece...connecting rods longer by the amount of thickness our new piece adds enough to put pistons back up to the top. Looong studs though everything from original locations tie the ridiculous thing together (once we add cylinder heads) and numerous extra studs surround the bigger chambers from just the upper casting through head...we can probably use the foundry down in the lunatic asylum's hobby shop, right??
  14. mustangsix
    Joined: Mar 7, 2005
    Posts: 1,379


    The perfect flathead v8 would probably use a SBC crank, rods, pistons, timing cover, timing gears, oil pump, water pump, and maybe even a SBC roller cam. Bellhousing and pan would be SBC as well as the starter. Use the SBC distributor.

    Then some enterprising person could cast up some Ardun style heads to convert it back to OHV!
  15. gearheadbill
    Joined: Oct 11, 2002
    Posts: 1,313


    This one of those 'joke' threads......right?
  16. Perrorojo
    Joined: Feb 25, 2011
    Posts: 357


    I convert nice pieces of sheet metal into little chunks of scrap every time I try to do bodywork. I don't see why you can't do the same with an engine.
  17. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,347

    from Quincy, IL

    Bruce, as usual, you are on traget..........but the attitude :eek:........... what happened at your birthday party :confused:........:D

  18. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,681

    Bruce Lancaster
    Member Emeritus

    Hey, I'm OOOOLD now! Attitude? I'm already designing the cores for the water jacket! Was gonna use this clutter of Chevy blocks, but they are too tall. Gotta find some NEW scrap to ruin! Somebady call the guy with the Ferrari motor, 50 ponds of welding rod, and sawzall. We are going to need his skills. It has to be running in THREE DAYS to get to the Jalopy drags at Beaver Springs!!
  19. nick_s
    Joined: Apr 11, 2006
    Posts: 436

    from Ohio

    you could do this and save yourself stepping back 70 years in technology

  20. he wants an aluminum block so he is probably going to have to use an all aluminum LS. Or maybe an OHC Vega motor.
    Funny thing is that I believe that the flathead is the new SBC so if you do it to an SBC you end up with a double belly botton.:rolleyes:
  21. Can I puke now!!!!!
  22. I won't slam you for musing through your fingers and's healthy to let the mind wander to "what if?" territory and I have to admit, your post got me wondering about it.
    After about 19 seconds, my conclusion is it wouldn't be cost effective and way too complicated to attempt but! may make more sense to actually come up with a brand new flathead design from a clean sheet of paper. With the millions of hours engineers have spent since the last flathead was produced regarding making modern engines more effecient, it would be fun as hell to come up with a "new design" flathead engine. Make it from light alloy like aluminum alloy and cast any bellhousing pattern you want into it...maybe several variations of bellhousing patterns...
    Modern technology would give you the most efficent combustion chamber, valve timing, revised cooling and you could also play with modern coatings to help keep Exhaust heat away from the cooling system. YOu could cast any motor mount mounting you wanted....make it with as many headbolts per cylinder you needed for turbo charged engines.....hell, the possibilities are endless and the dreaming is fun..
    Good on ya for the thread.
  23. Tim
    Joined: Mar 2, 2001
    Posts: 16,402

    from KCMO

    How to convert an overhead motor to a flat head motor.

    Step one: pull vehicle into shop
    Step two: attach hoist to engine and remove all attachments to said overhead
    Step three: remove engine from vehicle
    Step four: attach flathead of choice to hoist, I suggest a caddilac
    Step five : attach transmission adapter
    Step six: lower new flathead into vehicle
    Step seven: with motor mocked into position build new motor mounts
    Step eight: connect fuel, wiring etc.
    Step nine: swap you radiator for one with the proper holes
    Step ten: enjoy! You just converted an overhead to a flathead in under 10 steps!
  24. pinkynoegg
    Joined: Dec 11, 2011
    Posts: 1,136


    maybe not converting an ohv to a flathead but it would be pretty cool to make a new block that takes sdc or sbf parts. save on cost and would give you more displacement and possibly more power. with the advances in technology it would be a better running flathead than the previous designs.
  25. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,856


    You could design an intermediate head (really a cylinder extension) that contains the valves and the ports, and then use really long connecting rods and valvetrain, ignoring for the moment the necessary splice in the cylinder wall (sleeve it?). But overall, why, why, why would you bother doing such a thing?

    As it always has been and always will be, the flathead combustion chamber design just can't flow as well as an OHV.

    I can understand a repro alumininum flathead block that accepts OEM parts, even a bigger displacement and better flow characteristics, but converting an OHV is like converting a DOHC to a rocker arm engine.
  26. Uh two words...........uh no
  27. Long time ago Nick Arias made hemi heads for Chevy motors. Now that was a good direction, but even so, they were not cost effective and therefore are rare as hell today.
  28. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    Member Emeritus

    You could convert an Ardun OHV engine to flathead, if you were so inclined. I first built the OHV Plymouth banger and then the flathead. So you could kind of say I converted the OHV engine to flathead. I think converting an OHV engine to flathead is doable as long as the engine started out as a flathead.

    Attached Files:

    Last edited: Sep 26, 2012
  29. OoltewahSpeedShop
    Joined: Oct 18, 2007
    Posts: 3,103


    Just pull 4 plug wires off your SBC and leave the hood closed. It would run just like a flathead. After a while you could convince yourself you really had one and save all this trouble.

    When you finally got tired of not having any power... Just throw the plug wires back on and you did an instant SBC swap.

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