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Flathead horsepower help

Discussion in 'The Hokey Ass Message Board' started by jaden, Oct 12, 2010.

  1. jaden
    Joined: Jul 3, 2008
    Posts: 35


    Hello everyone, first I should give you some background on what I’m trying to do. I am currently building 29 roadster, for which I have picked up a 53 merc flathead and 8 Stromberg 97’s. I am looking to build the most powerful flathead that I can using what was available as of 1955. I would like to hit the 250 to 300hp range. But I need to know every little trick in the book. I have looked around the hamb but other than the posts by bored and stroked and rat bastad about releaving/porting and grinding the crank i am having trouble finding what else I can do? I am not against supercharging but would like to stay away from that if possible. I am currently planning on lightning the crank and flywheel, port/polish and bore the block as much as I can. Could anyone tell me how many 97’s I’ll need or can run after making these changes and any other mods i can make? Thanks for your time and help.

    Attached Files:

  2. You don't have enough money to make 250 to 300 hp.
  3. AJofHollywood
    Joined: Oct 3, 2008
    Posts: 637


    Best of luck to you... this is what you are thinking of:

  4. Good luck. My 286 in Merc made 118 at the wheels. 250-300 is alot!
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  5. AJofHollywood
    Joined: Oct 3, 2008
    Posts: 637


    Realistically, 150hp is enough for a 29 roadster. I currently have a completely stock 8BA, in my roadster, and it feels right.
    But if you were to rebuild that Merc, put in a street cam, 3x2 intake, headers, some new heads, lightened flywheel --I guarantee you will be more then happy with the look & performance.
  6. NoSurf
    Joined: Jul 26, 2002
    Posts: 3,904

    from Chester NH

    That's easy- You'll have to build 2 flatmotors and hook them together.
  7. R Pope
    Joined: Jan 23, 2006
    Posts: 3,101

    R Pope

    Four 97's are lots for any flathead, even an Ardun.
    300 horses is wishful thinking. Too much bore, over about 1/8", makes a water heater!
    Port, relieve, stroke, bore, cam, carbs and compression are about it for an unblown flathead. 200-225 HP in the real world is a realistic figure for a driveable, reliable engine. If you want more, build a monkey motion motor!
  8. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,362

    from Colorado

    You know that for fact?

    I'd PM Bored&Stroked- he's a good guy, and very knowledgable. I imagine, that the only way you'll get 300 hp is with a blower, and a LOT of money.

    Bored&Stroked, Rustybuckit, and I are building a Cadillac flathead that should reach 300 HP. If you're serious, it will take time, and again, a LOT of money.

    Good luck- If you do this, I hope you post a build thread.
  9. Capitan Insano
    Joined: Apr 29, 2007
    Posts: 282

    Capitan Insano

    A 471 blower motor can get 300hp. An ardun with a 471 like the cover of rodders journal is about 375-400 depending on bore, stroke, boost.
  10. tubman
    Joined: May 16, 2007
    Posts: 1,958


    I'd say that to get a dose of reality, you should buy a couple of books; Joe Abbin's second one and George McNichol's. Both of these guys have surveyed some high end flathead builds with lots of dyno runs. Bottom line? If you want over 200 HP unblown, expect to spend lots of money and you will probably still be dissapointed. Abbin's book especially really gets down to the nitty-gritty on this.

    That being said, true 150 to 175 HP in a light car will put a smile on your face.
  11. Blown35
    Joined: May 20, 2008
    Posts: 128


    I agree that for 300hp you will have an exotic build on your hands and a blower is a must in my opinion. My -39 Coupe is normally aspirated with 2 97s - is near the 200 mark for hp - build as follows:

    1948 Canadian “L” block 59L
    Block stock - not drilled for “free flow”
    Hot tanked/ stripped and cleaned, magnafluxed and pressure tested.
    Cylinders bored 3 3/8 with 4 1/8 crank – 296 cu in
    Ported & Relieved
    Main center bearing support w/bridge cap and center bolt
    Balanced & Blueprinted
    Ross 9.5:1 Pistons
    Stock Ford rods
    Nielsen FH-365 cam - Duration 280, Overlap 244@050, Lift 365, Centerline 108
    Manley Pro Flo 1.6 valves
    Johnson adjustable tappets
    Navarro (vintage 50’s) dual carb intake
    Dual Stromberg 97 carbs 42 jets with 71 power valves
    <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:eek:ffice:smarttags" /><st1:place w:st="on"><st1:placeName w:st="on">Motor</st1:placeName> <st1:placeType w:st="on">City</st1:placeType></st1:place> Heads (early aluminum heads Mark Hietz – hi-flow)
    Fenton Headers / custom dual exhausts with Brockton Melotone mufflers
    Electric fuel pump (no mechanical can be added as pushrod hole is plugged and cam bearing turned to close hole)
    2 piece truck oil pan
    Oil Pump - Motor City M19 High Volume (49-53 kit)
    Oil filter external mounted Fram part # FL1
    High Torque starter
  12. M.Edell
    Joined: Jun 5, 2009
    Posts: 4,106


    DOin a 304" stroker,All the good stuff,Weiand 4x2,etc etc..It might reach 225HP when all is said and done..
  13. Nat aspirated or without a blower is not conducive to the kinda car you are building and its intended use.

    Go with a blower and move forward from there.

    Build the best /strongest short block you can afford with quality parts (that you won't see) so it wont take away from the look you want.

    Why not build a nice GMC blown FH with all modern/quality internals with rebuilt vintage/era correct induction. You will make nice , RELIABLE power that will still look traditional.

    Aint no fun having 300HP and not being able to drive it or be stuck on the side of the road.

  14. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,362

    from Colorado

    Good points- Good advice, IMHO
  15. Very good advice and so very true.

    You are not going to be able to get a streetable flathead with the kind of HP you are wanting. If you stay naturally aspirated you can realistically expect around 175 hp, if you want to step up to a blower you can get upwards of 260 -280 hp with a very reliable, drivable engine.
  16. Pete1
    Joined: Aug 23, 2004
    Posts: 1,475

    from Wa.

    Yea, it can be done but you won't like it because everyone you tell about it will call you a liar.
    That's why I quit telling anybody anything. Let them do their own research.
    The guys that write books are writing about street engines..You are talking about a street driven race engine..Big difference.
    You may have enough money to do the project but you can build 3 SBC's for the same ammount.
    Nostalgia costs money, how old do you want to be?

    If you get it going, go out and get some timing slips from somewhere reliable and then when people call you a dipshit, flash the slips in their face...Shuts them up every time.

    To all the people that tell you it can not be done, ask them how fast they have made their flathead go.
  17. buster6972
    Joined: Apr 3, 2007
    Posts: 156

    from Iowa

    Not raggin but why can't anyone just take a look at porsche. Horsepower is not everything if you could get 150 out of that block and drop some weight you could have a significant increase when compared to the stock block.
  18. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,362

    from Colorado

  19. jaden
    Joined: Jul 3, 2008
    Posts: 35


    Your quite right, but i never have enough money for anything i want so as my dad says i poor boy everything. I make some very nice stuff out of junk people throw away. It just takes me alot longe to do it.

    AJofHollywood i wish i could have that motor, to bad no one is remaking Ardun parts, hhhhmmmmm do i smell a business idea:rolleyes:

    NoSurf now your thinking!!! but two motors might be a little heavy for my A frame, please dont crush my hopes and dreams telling ,me that 300 horse will shread my frame either i got that covered.

    38FLATTIE Thanks for the heads up i'll probably try picking his brain, i'm just a little leary to Pm people, i dont wanna be a hassel, but i would love to see a build post on that engine.

    tubman just having my car rolling will bring a smile to my face but im a very competitive guy and i found my friend a 67 mustang fastback with a 428, and im not sure if i could live it down if he beat me;)

    39Deluxe sounds like you got a swell machine, but when you mention the stock block no free flow are you refering to the water jackets? i was thinking of reaming mine out to lose weight if nothing else.

    rat bastad you make a good point and i think thats the route i will go, i am just a little leary about the supercharger as a couple guys told me the 97's would not work well with a supercharger that i would need a good blow though carb. i was planing on using a custom set of pistons with anti friction coating on the skirts and a anti heat ceramic coating on the crown to minimize heat transfer to the engine and keep as much in the charge as possible, but what no one can see will be our little secret, do you have any sugestons for the crank and con rods? i have been looking at a cross fire crank the 180 degree ones how much trouble would my ignition and timing be with one of those?

    Thanks for the advice guys keep it coming, also if anyone has come across any builds or web sites about flathead builds im all ears.

  20. Dynaflash_8
    Joined: Sep 24, 2008
    Posts: 3,009

    from Auburn WA

    i hit 205 at the crank on a Plymouth flathead. Didnt last too long though.
  21. hotroddon
    Joined: Sep 22, 2007
    Posts: 16,120


    Uh, They are being remade. The cylinder head conversion kit starts at $13,950.00
    Last edited: Oct 12, 2010
  22. jaden
    Joined: Jul 3, 2008
    Posts: 35


    ha ha depends how old the junk is i pull out of the scrap heap, but i was shooting for pre 55 as any older and i start getting into the muscle car era and i'll have a different build for that era. as for the timing slips i dont bother with the braging rights, i'd rater have the competion be blindsided than give them a heads up. no matter the sport motocross, super bike, formula or just mo ped the other guys always seem to make their ways to my machine to have a look at whats be done.

    No it sure isn't and i hope to shed as much weight as i can but it kinda feels like im just trying to catch up rather than get ahead in the weight department with the flathead. Thin wall casting techniques have come a long way since they were made. but maybe the weight of the small car can offset the motor. And if i put the motor in the trunk i'll get the right weight distribution:D
  23. jaden
    Joined: Jul 3, 2008
    Posts: 35


    AAAAAARRRRRRRGGGGGGG are you kidding me! i'm gonna be broke forever. you dont suppose there is some head off another type of engine that i could modify to fit on the flathead? maybe a hemi or something?
  24. AJofHollywood
    Joined: Oct 3, 2008
    Posts: 637


    Jaden, I can tell you are a little new to this stuff. Please take my advice... build the car, simple --just make it go & stop. If you have a running flathead, don't touch it --install it as-is. When you are ready to modify it, do it one part at a time. I suggest, start with an intake, then headers.
    When you graduate college and are making some money, then go crazy on it. Until then just make it drivable. These words come from experiences and mistakes I could have lived without, but learned from.
  25. jaden
    Joined: Jul 3, 2008
    Posts: 35


    Hi AJ thanks for the advice i wish i could take it but the first thing i had to do was tear the engine down before i got it. you see if i wanted the engine i had to lift it by myselft into the back of my car so i tore it down to a bare block minus the cam and valves and even that almost gave me a hernia humping that into my trunk. i got it all home but i tossed the pistons as i figured i would be finishing the engine before instaling. I now wish i had it all in running condition but it's not all bad im in no rush and it will proabably be another couple years before i am ready to install the engine. As for being new to this hobby, im not i was a mechanic throught high school and built race bikes and sleds of every flavour along with a few special interest cars like gto's a 66 mustang and a couple formula carts. I would liket to think of myself being capeable just new to flatheads. I figured i would see what everyone else is doing with theirs before i sit down and start mine.
  26. NoSurf
    Joined: Jul 26, 2002
    Posts: 3,904

    from Chester NH

    Read this book:

  27. HeyyCharger
    Joined: Dec 8, 2008
    Posts: 929


    Point well made!


    Although I haven't built a Flatty yet, and still earning the bread for the build....... I can tell you that I have been doing excessive research and questioning many Flathead veterans about my plans/goals in which are very similar to yours!

    Let me tell you one thing, I have posted up a couple threads on this exact topic and got the some excellent advice, (E.g Rat Bastad, he knows what he's talking about, has built a couple motors which have run excellent etc etc!) yet, everyone who rebutts my idea and goal never seems to have actually built such an engine.

    To the veterans/pro's reading this, please don't think I've got my head stuck up my ass, but, Unlike 'Pete1', no one says their points from shear experience!

    Just for the sake of the post, I am looking at building (long term build) a 304ci Flathead.

    4 1/4" crank, 3 3/8" bore, I won't even bother getting into all of the details.

    I am still juggling the aspect of throwing on a 4/71 blower as well......

    Approxiamtion of Hp Naturally Aspirated= 200-250 HP.

    Approximation of Hp Blown= 250-300 Hp.

    But once again I'm not entirely sure on these numbers as I need to find more people who have actually built these motors.

    My main man on this research is 'Pete1'! He has built many of these motors and even raced a couple of them on bonneville back in the 50's!

    He swears that this build is possible and that it's drivable..... Nevertheless, and no disrespect to Pete, the research is a whole lot more intense than that, though Pete always seems to have an answer for all me 'conservative' queries.....

    This guy know his stuff, drop him a line, he'll be more than happy to help...... But, make sure you listen to the rest of the guys here..... If you have all their points in mind also, you look out and keep guard on the negatives that could be introduced on such a big bore/stroke. And yeah, a build like this is a big risk..... That's why I am still planning on just rebuilding a stock 8BA Flathead, throwing a set of headers, 2 Deuce intake and getting this AV8 Roadster build under way...... The 304 is going to take a lot of money and time so it will be on the side, but will be built slowly, and surely.....

    A build of this sort takes a LOT of research and studying.... Get it wrong, and you'll have 10-17k worth of Flathead motor sitting on an engine stand waiting for a rebuild.......... This is a big project, not a SBC your messing with......

    Don't be afraid to post up threads, send plenty of PM's to the pro's, e.g, rat bastad, bored & Stroked, Flat Ernie etc etc..... That's what this FORUM is ALL about!!

    Yes, the issue of this motor being a 60 year old motor, with rusty jackets etc etc is apparent and it ain't going to be easy finding a block.

    But as you said, I am competitive also.

    I am still doing a crap load of research and I may be annoying to some people with questions, but that's the only way........

    In summary, take your time in researching, asking, annoying, thinking......

    And buy several books, as the one posted above, Joe Abbins is excellent too.... I have a couple on the way now.

    Also, I am not disputing your experience and knowledge, but I have learnt that the Flathead is a totally different beast!

    Not your average V8, and the fact that they have had water going through them for 60+ years doesn't help when boring out for big cubes!

    Good luck, and wish me some too!!;)

  28. Rocky
    Joined: Mar 3, 2001
    Posts: 12,321

    Classified Editor

    Go for it! Educate yourself, spend away and use the HAMB as a sounding board. I have several flathead books I'd send you if you want....I'm finally over flatheads at 62... I have MIke Davidson's "How to build the high performance street flathead" and Tex Smith/Cartech "The complete ford flathead V/8 engine manual" if you want 'em. I also have Bishop and Tardel's book but I'm keeping it because it addresses a lot more than engines and the engine section is better covered by the other 2 books anyway..
    Send me a PM with your address and I'll ship them but I'm gonna extract about 6 bucks for shipping..
    It's said the journey is a lot more satisfying than reaching the destination and when it comes to playing with flatmotors I agree. You'll laugh, you'll cry, you'll pull your hair out and you'll pay up the ass but when you reach my age you'll look back and feel a little richer for doing it. Please...don't expect too much outta the ol girl compared to modern engine designs...that'd be like comparing apples to oranges. Remember, Henry ford had the very best technitions and a huge pile of money at his disposal when he was trying to do the same thing you're doing..he was sucessful with some of it and and blew off some of it but after 21 years of tweaking with this engine he threw in the towel and went to a modern design...
    His reasons were more financial than any other but he'd had enough.
    Have fun with it!
  29. blown49
    Joined: Jul 25, 2004
    Posts: 2,213

    Member Emeritus


    My blown Merc flattie makes around 265 HP. It's 268 cu/in with a 400JR. cam, Mallory, Fenton headers, ported and relieved. My Merc weighs 3710 with me in it and it moves along pretty well.

    Go to http:\\ and order Joe Abbins's latest book ($25.00). Read it once and put it down for a day then pick it up and read it again and repeat until you get the facts straight then make a plan for your motor. His book has dyno info for blown and unblown engines and is well worth the $$$$'s.

  30. 38FLATTIE
    Joined: Oct 26, 2008
    Posts: 4,362

    from Colorado

    Jim, that's real good advice! I've read it several times, and learn more each time.

    BTW, I love that flattie of yours!

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