I've never had a running Ford V8 flathead, had one in pieces once that was stout in its day, but couldn't keep it. I've always loved these engines and thought them good for about 220 -240 horsepower. I just saw a dyno run on YouTube where a supercharged 59A put out 300 hp, 322 pound feet at 5300. What have you guys seen for horsepower on a flathead that could hold together?
Flathead powered anything are rarer than hen’s teeth out where I live. Even down at the Syracuse nationals the year before last, I think I saw maybe a dozen flathead powered vehicles. I’m thinking most are below 200 hp if naturally aspirated. I just watched the PowerNation YT again a few days back where assembled and dynoed a flathead and thought the numbers they got on the dyno were impressive - 160 hp.
When I was in my teens I drove a few flathead powered Fords. They were fast, fast, fast and had gobs of power. Fast forward 40 years and I bought a nice 47 Ford Coupe with a stock flathead. It ran perfect, but all the power I remembered from my teens just wasn't there (pretty sure it wasn't there in my teens either). A slow corner around town called for a downshift to second. It would accelerate to 60 fairly fast, but acceleration topped off quickly. I did get it up to 85 one time; it might have gotten to 90, but that was about it. In high school a buddy had a nice 47 with a flathead 6. It was pretty torquey, but he wanted more power. We swapped a 53 Mercury engine in the old car. The end result was you couldn't tell a lot of difference between the 6 and the V8. I think he ended up with a Y block in the car. Another buddy had a 39 coupe with a "full house" flathead. Edmunds finned aluminum heads, Edmunds intake with two chrome 97's. Another car I thought was ungodly fast when I was 14. He swapped the flathead for a 322 nailhead. I only rode in it one time with the nailhead, but the difference was amazing.
Naturally aspirated most will be, at best, in the 150-200 hp range. They don't make big power. Unless you spend even bigger money. Flatty's are adequate. Think about it. If you run a stock 100hp flathead around using all 4000-ish rpm regularly you are using the same revs of a modern 4 cylinder which is also making maybe 100 HP in that same rpm range. But the flathead will make more torque in that range than a 4 cylinder.
For some interesting reading on this subject, I would suggest a book named "Flathead Facts" by John W. Lawson. He started with a bone stock 8BA and added modifications and documented each step on the dyno. His results are quite eye-opening.
Mine made 136 hp at the wheels...that was in 2004. Ran pretty well in a 1500lb T-Bucket with a 5 speed and 3.78 gears.
Flathead Facts is a great book that cuts to the facts on modifying a flathead. If you’ve got a stripped down model a or 32-34 and it’s a healthy engine your gonna get a good seat of the pants feel from the torque. Or you can strap a blower to it and get a little more. Both are fun.
Just watched a dyno video of a blown flathead that made 300 hp at the flywheel. It had a lot of modification to get that much HP.
Because of the inherent restrictions of the "L"-head design, flatheads respond to supercharging better than overheads.
Using a GMC 471 blower a flathead can easily make 300 HP and be extremely reliable. I'm talking cross country and back at highway speeds all day long reliable if built correctly. A normally aspirated flathead will make up to 180 HP with what's considered typical mods that being porting and relived block along with at least 1/8 overbore. Attention to cam timing helps greatly as well as any stroke from 4 inch on up. The Red line for each build 5500 RPM. Since you asked about holding together as I wrote above if built correctly with good parts then 6500 RPM is also doable. Our hand built competition stock block 292 CI Ford flatheads burning gas that we run at Bonneville currently hold numerous records with speeds well over 200 MPH. Ronnieroadster
On an engine dyno, I made north of 320 on my 8BA. I could think it could have squeezed out a few more but I was close to squeezing out a massive turd watching the machine shop flog my expensive flathead (I need to never attend the dyno sessions). 471 W/8 psi boost, .125 overbore, 8.5 CR, MSD BTM6, massive amounts of porting, CNC mains...dyne pulls and break in were done with a 4bbl Holley the shop uses for such occasions and not my 97's. I gave Joe Abbins book to the machinist and told him to follow it to the letter. Like that short sighted, rather portly fellow in Jurassic Park, I spared no expense. I have been driving the car on the street for several years and other than a few fouled plugs, it will KEAL! I have friends that boast breaking 200 with normal induction. HP = $'s when building fast engines. HP = $$,$$$ when that engine is a flathead ford. Your friends at Jack Daniels ask you you to please build responsibly.
Found another YT vid where they dynoed a blown flathead. Must be from 2001 (Powernation - Horsepower TV Season 2/Ep 1). Made 260 hp. Loved Horsepower TV. Just learned that Joe Elmore passed away last year at age 80.
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