Am I missing something

[slowdown]

So I follow roadkill an hot rod garage. I just watched the last episode upgrading there fury station wagons brakes an top end of a 500cu something or rather stroker. An they were hoping to make 500 hp with this. After having this thing tuned on a dyno they got it in the low 400 ish power range. An they had some nice parts put on this thing. So my thoughts were if these guys who do this for a living an have what ever they need to build these engines, an barely clear 400 hp with this big stroker motor.( Not that 400 hp is anything to sneeze at)
How is it a lot of post I've read say something like 400 horses is easy to get with a 360? I guess I'm confused. Not trying to poke any bears I guess I'm not understanding how a stroker engine of that size an with those kinda parts isn't making a lot more ponies. Anyone else watch these?

 

[green dart]

They made 400 at the wheels

 

[diymirage]

They made 400 at the wheels

Which makes about 530 HP at the wheels (edit: that should be at the crank, not wheels)...and who knows how much torque

 

[abodyjoe]

Which makes about 530 HP at the wheels...and who knows how much torque

you mean at the crank??

 

[ScampMike]

yea - you gotta figure 25-30% power loss from the crank/engine to the rear tires... so 400 RWHP would be 500 or better under the hood

 

[MOPARMITCH]

you mean at the crank??

You mean on Crack ??

 

[slowdown]

yea - you gotta figure 25-30% power loss from the crank/engine to the rear tires... so 400 RWHP would be 500 or better under the hood

So 400 at the crank on a 360 would be less then 300 at the wheels?

 

[turtleheadjoe]

So 400 at the crank on a 360 would be less then 300 at the wheels?

Yeah, or maybe close to it depending on driveline. I've always heard 20-30% loss

 

[abodyjoe]

yea - you gotta figure 25-30% power loss from the crank/engine to the rear tires... so 400 RWHP would be 500 or better under the hood

I know what you meant. But it's not what you typed. Figured I'd straighten it out for the OP.

 

[ScampMike]

I know what you meant. But it's not what you typed. Figured I'd straighten it out for the OP.

LOL - that wasn't me

 

[diymirage]

you mean at the crank??

yes, that is what I meant, sorry

yea - you gotta figure 25-30% power loss from the crank/engine to the rear tires... so 400 RWHP would be 500 or better under the hood

I guestimated 25% drivetrain loss, so 400 HP at the rear wheels is only 75%. 400:75=5.3 5.3X100=530 HP at the crank

LOL - that wasn't me

yeah, that was still me, sorry

 

[Lustle]

It's kind of easy to throw out the 25-30 number. And in some cases it might be true. And can be generally close to accurate.

The reality is it's MUCH more difficult than that to figure out exactly the power loss through the drive train. As it is a curve, not a straight line graph. IE 400HP400TQ engine doesn't just automatically lose 100HP/100TQ just because it has a 727 and 8-3/4 behind it and a 500HP/500TQ doesn't just automatically lose 125HP/125TQ because its not a straight line. A 400HP/400TQ might lose 25% or 500HP/500TQ might lose 20%. But other engines might lose more or less. This is the problem with the whole "727's take X amount of HP" argument as well. Essentially it's a curve that depends on all the inputs (engine power, torque, where it makes it, transmission, transmission fluid, changes to transmissions, bands, rear gears, rear gear oil, etc etc etc). It's basically endless. It's similar to how we spec hydraulic motors at my work. A guy says "I want the motor to do 400 rpm and 20 ftlbs" so we say "Ok whats your input GPM and PSI" Guy says "Doesn't matter, just has to do 400 RPM and 20ftlbs". Except that it does matter. Every motor's output is dependent on the input. It's the same with the drive train loss. And with the almost endless combinations out there, it would be very difficult/next to impossible to come up with a general graph to show what you can expect. Basically. Build the motor you want. Worry about numbers later.

If my explanation makes any sense.

 

[ScampMike]

So 400 at the crank on a 360 would be less then 300 at the wheels?

it's an accepted general rule of thumb... a "guesstimate" - 300RWHP would give you somewhere around 375 (25%)-390 (30%) HP at the crank... approximately

 

[famous bob]

brings to mind a buddies superstock-55 chevy, made right at 400 h.p. at the rear wheels last time it was on the dyno. READ; 265 cubic inches !!! he has 18 walleys too.