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54 Pontiac Flat Head 6 performance build

Discussion in 'The Hokey Ass Message Board' started by micro, Oct 26, 2008.

  1. micro
    Joined: Dec 22, 2007
    Posts: 50

    micro
    Member

    Has anyone done a performance build on a 54 Pontiac flathead 6, whom would make the headers, intake, dist, what piston combo, would I be able to stroke this motor, and whom makes a custom ground cam for this. An finally is the bell housing part of the motor, or can I remove this and convert it to a 700r4 or a gluide.

    Tom
    tct546@yahoo.com
     
  2. 55chieftain
    Joined: May 29, 2007
    Posts: 1,783

    55chieftain
    Member
    from Canton IL

  3. micro
    Joined: Dec 22, 2007
    Posts: 50

    micro
    Member

    Thanks for the info
     
  4. HEATHEN
    Joined: Nov 22, 2005
    Posts: 7,585

    HEATHEN
    Member
    from SIDNEY, NY

    Edmunds made a head and dual intake (good luck finding either), and Mallory made a dual point distributor.
     
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  5. Zig Zag Wanderer
    Joined: Jul 6, 2007
    Posts: 563

    Zig Zag Wanderer
    Member

    HAMBer Bumpstick posed a similar question in the straight 6 thread; i'll repost my response here, adding a few bits and leaving out the cam advice, which you have well in hand. the cam that Vintakes has sounds perfect!

    there is SOME degree to which this engine has been hot-rodded. Eddie Miller also used one in his early '50's open-wheel streamliner.... this information is paraphrased and lifted from "How To Hotrod Your Car" by the editors of HRM (Wally Parks, Don Francisco and Racer Brown) c.1952 by Trend Books.

    the blocks are stout, and thick-walled. the stock 3 9/16" bore on the 239 six can be bored .187 to 3.75" without sonic check. that gives 265 cubes with the stock stroke of 4". these have insert mains and rods and a good full pressure oiling system. the book recommends line boring the main saddles and line honing the inserts to size. (think about purchasing slightly undersize bearings and having the journals hard-chromed back to standard spec to accomplish this). the crank and rods are forged and hella stout, in fact the rods used to be much sought after in the Model B/C Ford crowd for use in those engines. also, in fact, the best approach to building this engine is to think of it as a 6-cylinder version of a Model B/C Ford, with a skirted block, already converted to full pressure and inserts, that you can get absolutely no speed equipment for; you will have to make or adapt everything.

    the book says to discard the 2-pc wristpin bushing and use a bushing that has a .060" heavier wall thickness, requiring boring the small end, but does not state a source application...it says also to use 1938 Dodge truck wristpins (any of you Mopar flat-six guys got a diameter on those?)

    the stock pistons are cast iron. six of your best friends who are smokers just got new ashtrays....don't know about compression height but there are a lot of engines out there built in the last 50 years with around a 3.75" bore. something off the shelf might work.

    valves up to 2" can be fitted without head gasket interference; and should be as the stockers are too small to make power. the block should be relieved 1/8". the stepped area over the exhaust valve should be flycut an equal amount to the amount the head is milled, of which .183" is the maximum cut. a combo of filling the chambers with weld and milling should be the plan with a flat-top piston, probably best zero decked with a very slight flycut above the bore after filling. sparkplug location is poor, limiting your compression to 8 to 1 without detonation.

    Edmunds did make a dual-carb, but it has to be hens-teeth by now. if overbored to 265 the engine could end up needing more carburetion than the Edmunds could provide anyway.

    make your headers, copy what works on A/B/C Fords as far as primary length and diameter.

    an intake could be easily made in the log style, think about a 4-carb built for stromberg 81's patterned after the Howard's 5-carb GMC 6 style.

    ignition; all the book says to do is consider a magneto....may still be the best advice. i'm sure a base will have to be adapted by now. if you use a vertex make sure it's advance curve is not locked out for racing. any mag shop can unlock, recurve and test the unit economically and it's money well spent.

    Dyna-Flyte offered a dual-point breaker plate to convert the original Delco distributor using Delco d103 points. a good, properly set up dual point with a big old Mallory Voltmaster and an MSD-6 under the dash is still a pretty serious ignition and nothing to sneeze at.

    lighten the flywheel, or step right up for a custom aluminum one...
     
  6. panic
    Joined: Jan 3, 2004
    Posts: 1,456

    panic

    It's a great idea.
    Everyone makes speed equipment for that engine, just go down to Walmart and pick them right off the wall.
    Open the package, and they install themselves.
    Instant 500 hp.
     
    Last edited: Oct 27, 2008
  7. Zig Zag Wanderer
    Joined: Jul 6, 2007
    Posts: 563

    Zig Zag Wanderer
    Member

    christ panic, here we go again.
     
  8. RichFox
    Joined: Dec 3, 2006
    Posts: 6,663

    RichFox
    ALLIANCE MEMBER

    Eddie Millers engine
     

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  9. Wow !!! Who knew that Wal Mart even carried that stuff ?
     
  10. panic
    Joined: Jan 3, 2004
    Posts: 1,456

    panic

    I'm really confused.
    When someone who appears (to me, but my perspective is 45 years of involvement) to be someone who wants to do something himself (Yay!! always good), but has picked an obscure and (my opinion) not especially good candidate for a subject.
    I don't want him to buy a crate motor. I don't want him to do what everyone else does.
    I want him to understand exactly how difficult this will be, given the lack of aftermarket stuff, and the scarcity of information.
    I also suspect that he will be disappointed in the end result, in how long it will take, how much it will cost, how much work simply must be fabricated (by whom?), and how much power results.
    Is he still set on doing this if it takes 2-3 years, costs $3,000 above the cost of rebuilding the motor, and results in 150 hp (far more than stock, but not what I would call sparkling given a heavy car)?
    An example of $$$: "the book recommends line boring the main saddles and line honing the inserts to size." Except the 4 main journals are 4 different sizes. That means 4 passes, done in order.
    The stroke is not bad for such an old design, 4" (same as BBC 454) gives a mean piston speed of 3,500 f/m (pretty safe for a quality piston) at 5,250 RPM. Based on probably having long rods (common practice then), the max RPM @ 80,000 f/s/s is about 5,800.
    I'm not sure the huge bore sizes popular "in the day" were a good choice, since they were based on the "if you can't see through it, and it doesn't leak - run it" method. Even up through the 1960s, Jenkins was yelling "yes, you got an extra 3" out of it, but you have no ring seal!!!". I'm pretty sure +1/8" (.125") is safe, and perhaps 5/32" (.156").
    Pistons with flat tops in 3-11/16" (+1/8", or 3.6875") include 325" Dodge poly, 273" LA (oversize), late Ford 6 200/250 (oversize).
    The engine does have a big advantage (based on the LSR photo): individual exhaust ports. This means that joining the 1-2-3 and 4-5-6 is as effective as it would be on a Supra today - a long tuned header will work very well, but it will be a pain to fab and fit to the car. Primary tube: no more than 1/8" larger than the port ID.
    The intake should be made, not only because an original is going to be $$ but we know more now than they did (no one would use what we see on that race engine today). This isn't hard to do; the obvious choice is 1 progressive 2 bbl. on each group of cylinders front and rear. You need about 150-200 CFM per carb, but progressive gives better mileage and response.
    A log is easier to build but IMHO won't provide the same idle quality or mixture distribution.
     
  11. shpotty
    Joined: Aug 14, 2007
    Posts: 247

    shpotty
    Member
    from New Jersey

    They switched to aluminum pistons in the six for '53 and '54. The eights had iron pistons the whole production run.
     
  12. panic
    Joined: Jan 3, 2004
    Posts: 1,456

    panic

    The Pontiac appears to be (what the British would call) a "10 port" motor: 4 intakes + 6 exhausts (like the Ford 223), which was quite advanced compared to the more common "7 port" (3 intake + 4 exhaust) found in other inline 6s like the 235, GMC.

    A Ford 223 intake manifold (although too short front to back) may be close enough to modify by splitting into a front and rear section, rather than a complete fabrication.
    [​IMG]
     
  13. 55chieftain
    Joined: May 29, 2007
    Posts: 1,783

    55chieftain
    Member
    from Canton IL

    Did you get to check to see if your head was stamped "high compression"? One advantage of it being a 54 over earlier years it has the bigger 2bbl already on the intake. If you can stand looking at one carb for now anyway.
     
  14. panic
    Joined: Jan 3, 2004
    Posts: 1,456

    panic

    I agree - if you have a big 2 bbl. now, work on the other stuff to conserve the budget. It will run just fine with only a jet change when complete, and this will bring completion forward in time with only some peak power missing.
    Since you have 6 exhaust ports, you may be able to salvage a header from another small 6, such as the Ford 170/200 just to jet the flange & primaries, then mod the lower half to suit the car.

    Do you know the size and shape of the intake ports?

    As was said, a bigger intake valve is a major help (at reasonable cost). If you can measure a dead original I can dig up some possible swaps. This kind of mod must be in the original plan, because it affects your chamber shape, final compression ratio, valve relief contour, and cam choice.

    Here's a generic SV chamber with "Somender Singh" style grooves, which IMHO are worth doing.

    Depending on where the water is, it may be possible to re-locate the plug. At the exhaust valve is preferred, but may not be possible.
     

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  15. unclechop
    Joined: Apr 24, 2007
    Posts: 275

    unclechop
    Member

    Ive got the head off at the moment I will measure the valves(pics any one?) tommorrow.
    I had the head shaved 0.040 (It needed that to clean up)
    Should I open the combustion chamber a little?
    I might measure the volume and work out comp ratio(dont want ping)
    Apparantly ive been told not to use extended electrode plugs
    could that also cause pinging??
     
  16. panic
    Joined: Jan 3, 2004
    Posts: 1,456

    panic

    Should I open the combustion chamber a little?
    To do what?

    I might measure the volume and work out comp ratio(dont want ping)
    Pinging in a flathead motor has one basic cause: too much squish clearance.

    Apparantly ive been told not to use extended electrode plugs
    could that also cause pinging??

    Never heard that.
     
  17. Hudsonator
    Joined: Jun 19, 2005
    Posts: 335

    Hudsonator
    Member
    from Tennessee

    That head example looks suspiciously like a Hudson. I have a friend in Texas that swears by the Somender Singh groove and performs the operation on his Hudsons.

    Rudy does good work, I believe that is his cylinder head in the picture.

    Good info Panic, keep these boys on thier toes.

    Hud
     
  18. 55chieftain
    Joined: May 29, 2007
    Posts: 1,783

    55chieftain
    Member
    from Canton IL

    Here's what the 239 head looks like in the first pic, second is the 2 carb intake(small pic), 3rd is the 54 Bonneville st-8 with the Zenith sidedraft carbs, always wanted to build a 6 cyl version, last is mine although more together at this point in duplicolor racing green
     

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  19. panic
    Joined: Jan 3, 2004
    Posts: 1,456

    panic

    That chamber looks very good compared to some older stuff. Note the angled "shelf" masking off the exhaust valve relief - allowing a more direct path from the intake relief (with the plug hole) to the bore. This also reduces chamber volume, allowing more compression without restricting breathing.
    The reliefs can be improved with a bit of die grinder work, but you have to have the final valve sizes set & seated first.

    That manifold is also pretty good. It could be modified (permanently, I'm afraid) without too much work to greatly improve peak power even with the original carbs. It could also be sacrificed as the donor for a more complex manifold - saves a lot of fabrication.

    Looks like good things can be done - if this is what you want...?
     
  20. 55chieftain
    Joined: May 29, 2007
    Posts: 1,783

    55chieftain
    Member
    from Canton IL

  21. plym49
    Joined: Aug 9, 2008
    Posts: 2,742

    plym49
    Member
    from Earth

    What is a Somender Singh groove supposed to achieve? Does this apply to any flathead with a similarly shaped cylinder head?
     
  22. CJ Steak
    Joined: Sep 23, 2008
    Posts: 1,379

    CJ Steak
    Member
    from Texas


    That sounds pretty good... but my Willys 226 flathead sounds nearly identical to that. Especially when playing with the carb... I can get it to idle down low like that car. On a cold start it sounds like it's got a healthy cam in it lol...
     
  23. I drove the wheels off my old 41 with the 239 six banger for years with no trouble except a rear main seal replacement. Even stock, it had enough power to keep up with traffic on the freeway, although I replaced the old 3.90 gears with 3.23s and ran a 30 inch tall tire. If you keep your 54 as light as possible [hope it's a simple series 25 tudor sedan] it shouldn't take too much to make you happy.
    My car was the small series coupe and weighed about 2900-3000 lbs. I drove it from Omaha to Bonneville and then to the HAMB drags and only had to go to 2nd gear once...coming over wolf creek pass at over 9000 feet.
     

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  24. I'd like more info on this too! Never heard of it before. After all the dyno b.s. with my Mopar, I now have a clearer picture of what I need to do to achieve my goals, but any additional tricks are welcome.
     
  25. Hi Guys,

    A quick google search reveals:

    http://www.somender-singh.com/

    Website looks like BS to me but who knows? Just has that snake oil feel to it :D

    Danny
     
  26. automotivebreath
    Joined: Oct 30, 2008
    Posts: 2

    automotivebreath
    Member

    Panic,
    Although the owner of that flat head claims good results, I believe its worth the
    extra effort to groove the heads in the fashion Singh recommends. Here's a
    Briggs head he did.

    [​IMG]
     
    Last edited: Oct 30, 2008
  27. panic
    Joined: Jan 3, 2004
    Posts: 1,456

    panic

    Seen it, not sure why he specifies that position?
     
  28. automotivebreath
    Joined: Oct 30, 2008
    Posts: 2

    automotivebreath
    Member

    I was referring to a simple groove milled in the head compared to the
    picture I posted where the groove is more opened to combustion.

    As for position, Singh says point the groove at the plug, I say point it
    between the two valves, may help disrupt reversion during overlap.
     
  29. micro
    Joined: Dec 22, 2007
    Posts: 50

    micro
    Member

    Thanks for all of the feedback and info it is off to the machine shop just have to firgure out the cam..

    Thanks
    Tom
     

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