How Much HP ?

[GTXREEK]

Hi

I Just had my 440 motor rebuilt , broke the motor in on dyno.Dyno tests came out at 457hp.i have 3500 torque conv,manual valve body, 4:10 8 3/4 rear.
my question

What is approximate hp at the wheels?

[66 Dartman]

380 if you use a 20% loss through the drivetrain

[66 Dartman]

I've seen 17% used as well. Which would be 394 HP

[GTXREEK]

i thought that your hp would be higher because of all gear ratios and stall speed ?

[66 Dartman]

The most accurate way to figure it without a chassis dyno is to use your vehicle weight as raced and the actual 1/4 mile MPH.

[66 Dartman]

No, You will always lose HP through your drivetrain.

[GTXREEK]

Thanks I will have to try that next spring.

[66 Dartman]

The gear ratio and converter work together to keep your engine in a specific rpm range which may or may not be ideal for your engine/chassis combo. The idea being to keep your engine in the sweetest part of the power curve through each gear.

[Mills]

Your Torque is multilied by your trans and rear gear ratio.

[GTXREEK]

so does that mean my torque is going to be real high at the wheels?

[451Mopar]

Overall there will be less power at the rear wheels.

I'm not sure how your engine was dyno tested, but here are some things that rob power when installed in the car:
Accessories like cooling fan, alternator, power steering, etc.
Full muffled exhaust system.
Air filter and hotter air tempatures from under the hood.
Drivetrain and transmission frictional losses.

Because of gear multiplication in the transmission you can get more torque, but at lower output RPM, so the power loss is still there. When the transmission has a 1:1 input to output ratio (drive) in a automatic, it is easy to get the rear wheel power at the tires on a chassis dyno, or a vehicle dyno like DynoRad is selling.

Anyhow, for most of our old Mopars with Automatic transmissions the power loss can be about 20%. Manual transmissions are a bit more efficent.
My Car puts out a bit more than 450HP at the rear wheels

[dave571]

A local guy here, who has both dyno's, says he virtually always sees a chassis value that is .8 times the engine dyno reading.

As to the torque, the most torque is at the rear wheels. Most accurately at the axle center, and is reduced by tire diameter.

If this wasn't the case, there would be no need for gear reduction in the trans and differential.

[charger_dan]

I realize this is only a partial answer to your question, but I read (somewhere) that a stock TF727 requires approximately 45 horsepower to operate.

Talk about parasitic loss! Ever wondered why the 4-gear cars almost always produced better E.T.s in those old magazine tests?