8ba RPM

[Pete]

Originally Posted by quickchange34

I agree with Bruce the bottom end will take alot more than the breathing will allow. You really cant over rev one. They will run out of air before they blow. The valves will float. Even with a roots blower and all of the port and relief work they will give it up at 5500

Is that the absolute last word?

[Bruce Lancaster]

The last word, until you dangerous radicals chime in!!

[Frank Miller]

Ok I am going to hijack the thread a bit. The chart posted was interesting but I notice the hp and torque curves crossing at below 3000 rpms. Modern charts will always cross at 5252 because hp = torque x rpm/5252. Was there some other method used to calculate hp back then. I like the way the chart includes the cylinder pressure. It is easy to see when the motor stops breathing. It was explained to me a long time ago that torque measures how much work a motor will do while hp tells you how fast it can do that work. Here is a link that gives some explanation.
http://www.vettenet.org/torquehp.html

[BrianCT]

Interesting to note on the chart that they are using 40 wt oil.
Wonder how much HP that cost them.

[flatjack9]

Originally Posted by Frank Miller

Ok I am going to hijack the thread a bit. The chart posted was interesting but I notice the hp and torque curves crossing at below 3000 rpms. Modern charts will always cross at 5252 because hp = torque x rpm/5252. Was there some other method used to calculate hp back then. I like the way the chart includes the cylinder pressure. It is easy to see when the motor stops breathing. It was explained to me a long time ago that torque measures how much work a motor will do while hp tells you how fast it can do that work. Here is a link that gives some explanation.
http://www.vettenet.org/torquehp.html

The equation shows that hp equals torque at 5252 rpm. In this case torque and hp are different at around the 2000 mark. Torque and hp curves are going to cross at at least two occasions in all engines as the horsepower increases. In this case, both figures would be very low if the engine could indeed rev to 5252 rpm. Off the chart in this example.

[BUBBAS IGNITION]

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INTERESTING THREAD FOR SURE ....

I have been watching this rpm issue for some time.
Our Bonneville flathead is a 276 C.I. in a 1949 Ford F100, we built this project for Bonneville in 2006 and ran there at 97.6mph on a (then) 101 record.
We ran the three mile section and at the 1-2 and three mile mark engine would turn 4300 rpm. All of us learned a bunch about the (air pump) engine and altitude on the salt. The engine performed perfectly and i knew at the end of the three mile it wasnt going to get any better without a bigger better pump.
We came back after a few same speed runs and found another 40hp in the engine on the dyno.
Now we are getting ready for the Willmington Ohio mile run and have made a few more changes including a five speed transmission. Looks like we need a few local test runs to attempt the correct gearing etc...
I will get some rpm numbers as soon as the weather clears up a bit.
BTW the record at Willmington ECTA is 101.349 mph.
We all know we can do that , right ???????????????

[Frank Miller]

Flatjack, Thanks for that. With the modern motors we see the cross at 5252 but they never go high enough for when the hp drops off and crosses again. Shows how low end these motors are.

[RooDog]

Please note that the HP scale is on the left margin and the TQ numbers, on a different scale, are on the right margin. If the number were sync'd, (50 Ft Lb & 50 HP on the same horizontal line, for instance), the graphs would look quite different. Since the graph stops at about 4200 RPM, the two curves would not cross at all and the torque peak would far excede the HP peak. Since Horse Power was, and still is, a magical marketing figure, it is stressed over torque, which in the real world, outside of racing, is more significant. Since HP is a function of Tq X RPM they will not cross a second time as long as the engine is still making power and not been shut off, or blowed up.... RooDog

[Bassman/NZ]

Charts, schmarts..... JWLs book is the real life proof of the pudding. Dozens of dyno pulls, real life facts and figures, not Fords made up figures.

[Ol' Ron]

Hard to believe, you can't get a100 hp from a 239 engine, no mater what you bolt on it. unless it's a supercharger. But install a cam, and!!!!

[Ronnie]

Originally Posted by Bassman/NZ

Charts, schmarts..... JWLs book is the real life proof of the pudding. Dozens of dyno pulls, real life facts and figures, not Fords made up figures.

Yup some dyno numbers are bogus but sound good when bench racing.Its not easy to get much more than 175 hp normally aspirated for the street.

R

[RooDog]

OK, Fellas, Who's "JWL" and what's the name of his book? Share the secret.....

[BillM]

OK, Fells, Who's "JWL" and what's the name of his book?

http://www.vanpeltsales.com/FH_web/f...oksforsale.htm

[RandyZ]

If you wind it up too high, the valves float and the exhaust will tag the spark plug, closing the gap!

Yup...come home a couple of times on only 4 cylinders.

Damn those L-100 cams pull hard.

[Ol' Ron]

I think JWL's book is the best Flathead book ever written. And I've never heard a flathead float it's valves, and don't know anybody that has.

[Ronnie]

Exhaust tagging ????

R

[Pete]

Originally Posted by Ol' Ron

And I've never heard a flathead float it's valves, and don't know anybody that has.

Not on a stock engine but I have heard it many times on race engines.

[Fourdy]

So what level of rpm do you fella's recommend using the crank journal support? Maybe I missed it.

Fourdy

[Pete]

Originally Posted by Fourdy

So what level of rpm do you fella's recommend using the crank journal support? Maybe I missed it.

Fourdy

It's not so much the rpm level as it is the hp level.
An engine that is designed to make 200 hp or more will live longer if it has steel main caps or some kind of girdle.

[Walt Dupont--Me.]

My dragster, 286 I made a strap for the center main, turns 5500 at the traps every run, broke the drive shaft at the tree and the tack went to 7100, it's still running strong. Potvin 425 and 3 carbs. Walt