Flathead question

L

LSJUNIPER

Senior Member
Hello,
Was wondering. If you take a stock flathead motor and add headers, aluminum heads and one of the intakes that uses 3 carbs, will this give the motor a good boost in HP??? I have a falthead motor I will be taking to the auto shop for cleaning and testing for cracks. If all is good then I want to rebuild it, but I want to keep it more of an old school build.
Any info will be appriciated...
Thanks
 
The answer is as easy as yes and no or as they say "as clear as mud".;) If the engine is in good working order and you install aluminum heads, headers and a multiple carb intake (I would recommend a two pot, not a three) you might see a slight increase in power however, to achieve a "good boost" you'll need to do some additional modifications particularly in the area of ignition. All of the "bolt ons" that you mentioned make excellent “eye candy” :D on a Flathead but that's about it unless you go all out to build a more powerful Flathead. That's my opinion, I'm sure there will be others.:eek:
 
Get JWL's book - goes in to what mods to make, how much they will net you, etc. It really boils down to the fact that no matter how "hot" a flattie you have, it comes down to your trans and gearing, keeping in mind how you want to use/drive the car. My avatar has a 5-speed, 3:54 gears, and 30" tall tires - I can smoke the tires if I want but I built it to drive long distance.
 
Like Tom says, if you want to race it (track engine) or cruise with it (street engine), there are very different modifications that apply to each outcome, final gear ratios and transmission also have an impact. Whatever you decide to do, have fun with it.:):cool:
 
Investing in JWL's book will allow you to make informed decisions and will save you a lot of money in the long run.
 
You can't get a 100 HP from a 239 Flathead by bolting stuff on it, except a blower. Read the Book.
 
You can't get a 100 HP from a 239 Flathead by bolting stuff on it, except a blower. Read the Book.

I don't believe that for a minute
 
Attached is picture of my '36 LB engine. Pretty much what you were asking about. Alu. heads, two 97's, MSD Ign., what I would call 3/4 race cam, and tube headers. It has a '39 trans and 4:11 gears.

I didn't have it dyno'd (wish I had)but I can sure tell a difference from the stock engine I had before. With the 4:11 gears its not much for touring, If I was going drive it more I'd probably change them. As others above have said it depends on what you want to do.
 

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John did just about everything you could think of to increase the power of the 239 test engine and only achieved about 95 HP. He then installed a Max#1 cam . the engine then produced aprox. .110 HP along with all the other goodies.. Believe it or not, it's very hard to get 150 HP from one of these engines and still have it street able.
 
Others have already said it better than I can. My 239 has been bored 80, Max1, Mallory electronic, Red's headers Isky 424 heads, Isky intake and Holley 390. It sounds great and pulls strong but really does not like to idle. Was in the drive thru line at the bank last week and while everyone was admiring it it stalled! The 39 toploader and 3:78 gear wind it up quick. I believe max torque is under 4000 RPM so I wonder why I did all that!
Determine HOW you are going to drive it, then build it.:)
 
I'm no expert so can only go off my personal experience but when I swapped to a set of repro Eddie Meyer heads and matching inlet on my early 21 stud I immediately knocked one and a half seconds from my previous best E.T. in the quarter.
Ran consistent 20.5 secs @72mph to start with then ran 19.001 @78 after the swap, no other changes.
A few more tweaks here and there and I'm now running 17.4 @85mph.
 
Bored .040 over, Max1 cam, Holley 390, Edelbrock heads, headers, flex fan and electronic ignition ( distributor set up by Bubba's). Don't notice much difference in speed, which is ok as I am not a racer. I use it to haul heavy loads in very hilly country. Noticed a big difference there.
 
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