Hot Rods Flat head red line ?

What's the safe RPM limit with a late flat head. It has a stock 4" inch Merc crank. Scat rods. ross pistons.

 

I had my 286" up over 6k once...it broke.

 

From what I have heard, the flathead is a lot like a truck motor. Personally I wouldn’t take much further than 4500, 5k rarely.

*disclaimer: I have never owned a flathead, so feel free to disregard my guesstimate

 

With 3.78's and 32" tall tires, what MPH would 6 grand on my flathead give me? God I'd be flying!!!! Or at least I'd feel like I was!

 

Hold onto your shorts Alchemy, you'd be flying at 151 mph! Greg

 

I did it off a light on the way to work one morning (may have been racing a co-worker). I managed to limp it into the parking lot. Called a friend and he brought his trailer to get it home.

 

FWIW one of our locals here is kinda well known for blown flatheads (Joe Abbin) and he uses 5500 red line on his motor. Lots of dyno pulls with it. When he has one on the dyno pulling 5000+ under load I tend to stand back, they sound like they are ready to come apart but never had it happen yet!
I've have ran mine flatheads up to 5000 on occasion, just can't push them farther, usually 4500 is the most I like. Of course mine have stock cranks, rods ect.

 

If you can get an Arden to do 6200 rpm https://www.rodauthority.com/news/video-watch-a-flathead-ford-belt-out-400-hp-on-the-dyno/ the bottom end can be built to stand these numbers. Makes me think they are self governing under load by the amount of air you can get in and out. Valve train weight is pretty much like an over head cam motor.

 

So What let go ?

 

After a 6-ish thousand RPM (second gear) pull at the drags last year, the 286 flathead in my '39 Ford (59A, Scat 4 1/8" crank, Eagle rods, Ross pistons, Edelbrock 8.5:1 heads and dual manifold) limped home. It made it back but with its tail between its legs.

Loss of oil pressure (still has some, but next to nothing at idle), a knock, and two cylinders low on compression. Haven't torn it down yet, the car is getting a 283 Chebbie swap while the Flat motor will probably end up in one of my Model As...

 

I run my 286" Flattie up to 4500 all the time in spirited driving. I wouldn't want to push it much past 5,000. I'm running a 1007B cam so it really is set up more for torque than high end HP. That said, it pulls hard from 1000-4500 with no dead feeling or does it lay over anywhere in that range.

 

I have my blown 8BA rev limited at 5000, just so I don't make a right footed error.

 

Good cuz all your pals at the pub will look like those two dweebs in post #3.

 

I have pushed my “built” 3 3/4 stroke(stock) to about 5500 using Isky spring ;around5200 for a 4 inch stroker, and my built .155 over stock bore and 4 1/8 stroker(289 inches) seems to lay down closer to 5000 revs. I have heard and read of de-strokers of 3 5/8 stroke pushing 6500 but don’t know of any running in this era. I believe Tony Nancy’s record setting blown model a roadster ran a big bore de-stroker around 10.50’s, but I heard it ran faster in the Willys before Nancy transplanted in the quick A roadster.

 

If everything is in good shape, 5000 is reasonable