farmallCMpuller
New User
How many rpm can I turn on a stock block M with 4 inch pistons? Can I turn 2500 without doing anything to the motor?
Thanks Zach
Thanks Zach
- Thread starter farmallCMpuller
- Start date
1965lonewolf
Member
DO IT ALL THE TIME - JUST MAKE SURE ITS BEEN GONE THREW AND EVERYTHING IS NEW & FRESH
james rumph
Member
You run out of camshaft around 1900 rpm .
Meaning your torque falls off very fast after 1900.
There also isn't any "bob weights" on these cranks like a car so rpm will kill the motor.
Meaning your torque falls off very fast after 1900.
There also isn't any "bob weights" on these cranks like a car so rpm will kill the motor.
jd b puller
Well-known Member
Lonewolf, you say you run 2500 RPM's. What is she doing at the end of the track?
Thanks.
Thanks.
buickanddeere
Well-known Member
Are you aware that increasing rpms from 1450 stock to 2500rpms? Increases centrifugal stress on the rotating and reciprocating assembles by 2.97 times over stock.
Going to 2051rpms doubles the stress from 1450rpm.
Going to 2051rpms doubles the stress from 1450rpm.
Little Big B
Member
Just out of curiousity, If I were to build a little B that spun 3500rpms, what would that be. begining rpm is 1375 according to NATPA.
What is your formula for that?
Thanks, Derek
What is your formula for that?
Thanks, Derek
jd b puller
Well-known Member
The formula would be
JD 2 cyl * 3500 RPMs + crazy operator = flying pieces
heavy hauler too
Member
You will crack your stock fan blade to.
Anonymous-0
Well-known Member
even though rpms causes more stress and usually does run past peak horsepower and torque . the kinetic energy from moving the sled faster and letting the motor pull back into its power range usuaally is a advantage over slower speed and a motor in its power range and pulling down out of its power range.
Little Big B
Member
Hahahahahahaha, thats a pretty elaborate formula.
There will be a little more thought into it than just turning 3500 rpms.... everything has to made to make and take advantage of hp and torque at that rpm level...
There will be a little more thought into it than just turning 3500 rpms.... everything has to made to make and take advantage of hp and torque at that rpm level...
farmallCMpuller
New User
Thats kinda what I figured, its not that I need more power from the engine, its that I need more speed, but I can't build enough HP to run 2nd gear.
jd b puller
Well-known Member
LBB, you've been talking to Josh too much, or vice versa. 
Keep it at 20% and put enuf cubes in it to do what you want. Safer that way.
The guestimator that I came up with was
HP = Cubes * RPM / 7500
7500 for a good efficient motor (typical puller)
10000 for a stock one
make it smaller the more efficient you make it. Not exact, but close enough to get you in the ballpark.
Keep it at 20% and put enuf cubes in it to do what you want. Safer that way.
The guestimator that I came up with was
HP = Cubes * RPM / 7500
7500 for a good efficient motor (typical puller)
10000 for a stock one
make it smaller the more efficient you make it. Not exact, but close enough to get you in the ballpark.
Little Big B
Member
Who is josh?
I want a better efficency that .25/per cube. thats the reasoning for the rpm.
I've thought alot about the saftey beleive me, im not just going to turn one that fast with all stock parts.
I have to get this casting thing down and then we might have something to talk about.
I want a better efficency that .25/per cube. thats the reasoning for the rpm.
I've thought alot about the saftey beleive me, im not just going to turn one that fast with all stock parts.
I have to get this casting thing down and then we might have something to talk about.
james rumph
Member
I have a M@W P-400 dyno and my Super M has spent a fare amount of time on it.
I built a stout 281 [450] that was in the high 70s in HP and it still required 1st gear.
A stock cam runs out of lobe around 1900 rpm so it is a waste to spinn it any higher.
I have spun it at 2500 rpm and made just over 100 hp with it but the torque was cut in half .
You need the torque to lug. I tried pulling with it turned up and it was a failure even when the rpm dropped down. Keep in mind a good governor won"t let it drop that much.
There is a "M" here in Michigan that was built by Lemmons that does spinn 2500 rpm but it is stoked to 426 and it is built to run those rpms. The gentelmen that owned it was telling me one day that he hated running it that high because of the life span of the motor. This was ans still is a very strong pulling tractor.
buickanddeere
Well-known Member
Centrifugal force increases with the square of the rpm.
Power to drive a centrifugal fan increases with a cube of the rpm.
Power to drive a centrifugal fan increases with a cube of the rpm.
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