Hemi VS. LS6 • The Dodge Challenger Message Board

by **PPPFFF** » 10 Feb 2004 15:42

I have a question? Chevys LS6 is the most advertised horsepower on a RPO car. That 450hp rating is at 5600 RPM. If a hemi 426 which is rated at 425hp at 5000 RPM was compared at 5600 RPM, what kind of horses are we looking at. Just curious. Patrick :roll:

by **dave-r** » 10 Feb 2004 16:11

Read the thread on Torque and Horsepower Theory.

It would depend on the torque curve. If both figures were peak HP readings then one makes 425hp and the other 450hp period.

If the torque curve was still rising with rpm on one or other engine (or even falling at a slower rate than the rpm is rising) then either engine could be making more HP at higher rpms.

HP does not fall until torque starts falling faster than rpm is rising.

So really without knowing what the torque was at every rpm you cannot tell.

Read what I wrote on the theory and play with the formula. Then you will see what I mean.

by **PPPFFF** » 11 Feb 2004 17:27

Dave, do you know where you can find Chrysler Factory torque curve charts showing this information. Rumors were the street hemi produced close to 500hp @ 6000 rpm where it could run comfortably. I'm trying to prove that the street hemi produced more hp then the LS6 @ 5600 rpm. A chevy guy got under my skin. Patrick

by **dave-r** » 11 Feb 2004 17:58

I think Chrysler kept this sort of info under their hat. It was not wise to let the competition or the insurance companies know the facts.

It has often been said (but only by hemi enthusiasts) that the Hemi made more power at higher rpm. Certainly it was built to breath at higher rpm than that. But who knows? It could all be BS. The street Hemi was very de-tuned from the race version.

If you come across any torque curves from the past we would all like to see them.

by **TX70Challenger** » 12 Feb 2004 6:25

What about my 318 at 9000 rpm? Been tryin to climb this one darn hill for the longest time...

by **72 Challenger (Hans)** » 12 Feb 2004 11:32

9000rpm 318 ?? Hmmm, where I read this before... :roll:

by **moparmaniac (owner4)** » 12 Feb 2004 13:23

Wonder if you can get that 318 from ACME or Wyle E. Coyote with a rocket pack strapped to it. I think someone is lost in Looney Toon Land. Although I've had some great laughs reading the subject to which you are referring.

by **dave-r** » 07 Mar 2004 11:46

From the book "HEMI" by Anthony Young.

"The factory rating for the street Hemi of 425 horsepower was right on. When we did a scuff test, we'd fire up a green engine (no hours on it) and run it at max horsepower for two hours. Those things made 425 horsepower like clockwork."

Ted Flack
Chrysler dyno tester.

by **PPPFFF** » 07 Mar 2004 17:36

From "Hemi Muscle Cars" by Robert Genat. "The Hemi's horsepower rating was listed at 425 at 5000 rpm, but Chrysler engineer Tom Hoover once stated that the street Hemi actually produced 500 horsepower at 6,000 rpm, a number Chrysler was hesitant to advertise." And in "Dodge Challenger & Plymouth Barracuda" by David Newhardt, "the "Elephant," so nicknamed because of the huge valve covers, could live comfortably at 6,000 rpm where the dyno registered close to 500 ponies."

When I look at other manufacturers horsepower ratings, most are at 5,400 to 5,800 rpms. I know more rpm's doesn't necessarliy translate into more horsepower, however with the hemi head design, 425 seems like a low ball at a conservative 5000 rpm's. Just my opinion. Probably wrong. But it makes for fun discussions. I love this board. Patrick :lol:

by **dave-r** » 07 Mar 2004 22:09

The fact that they "made 425 horspower like clockwork" lends me to think they must have all made at least that.