HOW Many HP's can you realistically get out of a Flattie

You'll get more grins per HP than any other engine!

 

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You'll get more grins per HP than any other engine!

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Heck, I'll just be happy to be grinning!
A smooth, dependable Flathead in my "A" is all I'm going for. HP... who cares!

 

Some noise from the past:
R&C April 1955: The Yates-Newmire flathead, run in the Chrisman dragster, Barney Navarro as unindicted co-conspirator. .060" over '46 Merc (248"), 3-71 blower, 50% nitro. 435 HP on dyno. Only a shakedown run, reached indicated 140 when cooling hoses blew and coasted through at 131. Cheap studs blamed. I believe there's more stuff in the next issue, but haven't found that yet.
Not quite a street motor (!), but interesting number.
From the 1955 HRM Annual, 1954 numbers: Engine/Chassis shown. Some OHV numbers included. Very little reporting of ET's at this time period.
Merc/dragster 125.69
'49 Olds/dragster 123.79

Sports car hill climb road racing in same book was dominated by a mix of early and shoebox Fords--actual sports cars humiliated by '34 Fords and such. No wonder they split off and founded their own silly hobby...

Some 1954 NHRA records:

'51 Chrysler/Fuel dragster 139.77
'27Tfuel roadster/'46 Ford 116.72
Comp Coupe Nelson Fiat/'42 Merc 123.05
'36 Ford/'41 Merc 103.27

A Fuel Roadster '32 Ford/'46 Merc 103.52
B fuel roadster '32 Ford/'53 Ford 86.30

Street roadsters:
A-'31 Ford/'51 Merc, 99.78
B-'32 Ford/'48 Merc 90.12
C-'29 Ford/'40 Ford 89.85
Gas Altered-'34 Ford/'46 Merc 100.41
Gas class A-'32 Ford/'52 Cad-93.09
B-'39 Ford/'51 Olds 98.58

 

My flathead will get in the neighborhood of 4000 HP and run on nuclear fission...

I'm planning on breaking the sound barrier in a 49 Merc.

Performance is relative. Choose your battles.

 

Depends on if yer talking Clydesdales or Quarter Horses.
The Budweiser Beer Wagon ain't fast, but it sure looks cool!

I asked my old man that question once and he said:
"Stock from the factory, 90 to 100 H.P."
"But after we hopped them up with cams and carbs and heads and headers, Hell. Some of them were probably pushing an easy 90 to 100 H.P.!"

 

More dusty numbers from the past: Found a 59A chart, looks the same as the prewar chart above with just very slightly higher numbers. Also has BMEP, compression, fuel, and friction curves--a very busy sheet of paper.

Here's a '51 Merc graph reduced to words. The '52-3 got a hotter cam, but don't have numbers for that engine:

1951 Merc engine:

RPM Torque HP
500 178(!) not shown
1000 190 37
1500 202 58
2000 206 77
2500 200 94
3000 187 107
3500 170 112
4000 147 110
I'll repeat prewar Merc here for comparison:

500 152 15
1000 171 33
1500 180 50
2000 182 70
2500 178 84
3000 168 96
3500 153 102
4000 138 103
That's all they wrote...

Looks like that stack of Merc cranks is worth keeping!
All flathead folk should run out and buy the current repro of my favorite childhood book, Roger Huntington's "How to Hop Up Ford and Mercury V8 engines" from 1952.
It has lots of engineering charts of stock and modified engines.
Also, my various USA and Canadian Ford service bulletins have numerous dyno charts, some with other info as the 59A chart I mention.

 

Thanks for the incredible amount of information. Do higher compression heads make the already slow cranking motor worse? Can you wire a tach backwards on a positive ground 6v?

 

It all comes down to cubic inches and cubic dollars . . . both are required to push the horsepower much over 175. You can build a nice 1/4" stroker, 3 5/16 bore flathead, ported/relieved - 276 cubes and make somewhere between 150 - 175. These are torque motors, so in a light car . . . with some low gears, you'll be surprised how they'll pull. A good strong 276 cube motor is easy to build, won't kill you on cost and you'll have a ton of flathead fun with it.

You can also spend $12,000 - 20,000 to end up with a flathead that is closer to 300 HP. Like all HP quests . . . the first 50% increase is relatively inexpensive, the next 50% triples the cost.

Or you buy a SBC crate motor for $6000 that makes 400+ HP . . . it is all about what you're looking for, what you can spend and what you can do yourself!

 

....Favorite Part about this thread.........Germ Posted the perfect answer for this question. 7 YEARS AGO!

 

wheeewww....all this flathead talk....sure beats that 1-900 - number....

 

my 304 stroker good for around 250hp maybe a little more

 

Here's what I'm up to....hehe Just getting ready to set this 4-71 on my rad flattie...we'll see what happens. Mitchell intake, 2 holley 2100's, a 4" merc crank, Isky cam and offy heads. Yep, thats a 700r4 AOD.

 

Those are great looking engines

 

I transplanted a 85 IROC motor (305, 215hp) in an 83 Camaro (3300#), only real mod was headers - would do 130 easily. Though it cut a 14.997 1/4 on street rubber it would get eaten alive by early Fords.

 

How much of the flattie's torque can be attributed to heavy rotating mass? In other words, if you lighten the crank and use an aluminum flywheel will you kill the torque numbers?

 

the flattie's torque can be attributed to heavy rotating mass? In other words, if you lighten the crank and use an aluminum flywheel will you kill the torque numbers?

Others can weigh in on the question above, which is a good one, but it's my experience that light rotating mass has a very positive effect on acceleration.

 

I saw a '39 Ford with a flattie pull 80 HP in a chassis dyno. People giggled at the number, I was impressed. It takes balls to put something like that on the rollers after the guy with the blown 502 rat motor just pulled 630-somthing. That said, the guy told me he rebiult the flathead in 1973 and it's just needed adjustment and routine stuff since. Lesson here is, keep it realistic and keep it running. We build these cars to impress ourselves as individuals, let the rest be damned.

 

Whats interesting about the magic 5250 rpm number is that is where the hp and torque curves cross paths on all our engines


Vergil

 

If you plan on abusing a flathead,like a 50's teenager,you WON'T be the SMARTER Strube brother. Hot rodding and flatheads are all about nostalgia. NOTHING sounds as great as a flathead with a wicked cam,and Smithy's mufflers. You can have a lot of fun with a stock drive train,but you can not dump the clutch on a Hot fllat head,without blowing the trans,or rear axle. Fix one weak link,and the next weak link breaks. The one weak link you can not fix,is 3 main bearings. I built a mild street engine for my 1800# T-bucket,for under $3000,and it is a ball to drive. My heavy 47 sedan has a 286 inch Motor City flathead,that cost $7500, fifteen years ago. It sounds wicked driving down the road,or idleing through a cruise night. I am a teenager again,only smarter now.

 

Mass of the flywheel will affect the moment of inertia of the rotating assembly which will impact the accleration/deceleration of the crankshaft, not change the torque. A large factor in a flathead's torque is due to its undersquare design.
Regarding HP that can be realistically achieved; attached are the corrected dyno HP/torque curves of a recently completed stroked 284 ci 8BA flathead built for reliable street use by Abbin and McGlasson. The engine was run both normally aspirated (3X2s) and supercharged (Weiand 142) to compare output:

 

Thanks

 

First tell us what your expectations are for engine life and collateral damage to your bank account.

Bob

 

We have a winner!!

 

Joe Abbin at Roadrunner Engineering in New Mexico has a book about his supercharged flattie that puts out 336 HP. He sells the blower kit and tells all about how to do it.

 

I gotta admit, even tho I love the looks of a flattie, I wasn't impressed with the power......... however.... I couldn't believe the torque this little shit put out. I have a stock '47 59l engine in a '29 roadster. It has three carbs, but only the center working. On this cars maiden voyage I had forgotten to put the plate on it. As I ran into town and around the block, my shift handle broke off flush with the trans. (t-5 with a stupid 3 foot handle) I came down the hill and turned a corner in 5th gear (3:55 rear). This 'ol flathead didn't even hesatate pulling around the corner. Kinda sounded like my dads old tractor, but didn't miss a lick, just kept pullin". A local cop saw me and just smiled and shook his head as I ker-putted out of town. Ya just gotta love these 'ol things.

 

Heres some of our real numbers from our Bonneville project truck in 2006. We have another new bigger motor with hilborn yet to test.
181 hp was our last shot ......

www.gasolinealleyshops.org

 

I've never paid so much to go so slow.
...but I still love my little flathead.

 

There is an article in the latest Bonneville Racing News about Rick Schnell's Blown nitro flathead. . Pulled 939HP @6700rpm.

 

Gil Ayala ran this full custom merc 129mph under flathead power.

 

Someone once asked an engine builder that same question, answer was "How much money you got?"