A friend of mine at work and I have been arguing for the past few days about the real power output of the 426 Hemi. we both know it was rated at 425 horsepower, but I belive the real output must have been closer to 500. He on the other hand doesn't even believe that it was making 425. So, I figure I ask the experts, how much power did it actually make?

We are going for engine power not RWHP.

 

It's been said for years that even when stock, if correctly tuned, it could make 425 with one plug wire pulled...... True output at the crank was more realistically in the the 460-470 range.

 

Yep, what Tee said.

Countless car mag reviews over the years have shown a properly tuned street hemi (stock) was putting out high 480-525 HP. These motor are incredibly responsive to ambient conditions which helped bump numbers in some of those test. Either way, you win.

 

From the Hemi History book they said 425hp was only as far as they were willing to take the 426 Hemiup to because the Dyno was only rated up to 400Hp and they were affraid they were going to break the dyno if they pushed the motor anymore. Its real power was around 500hp at 7,000 Rpm.

The book also says they ran 426 Hemi engines for 2 weeks straightat 8,000 Rpm to test its durability. Towards the end of the 2 week period motors would self destruct heads fly through the roof and even a report of a motor glowing orange and melting on the test table. They cleared the motor for production after tests concluded it to handle 8,000 Rpm for the 2 week period.

Dick Landys 1968 Dodge Charger was pretty much stock with the exception of Headers no air cleaner, slicks and advanced timing and he ran 10.30 1/4 miles at 130mph and the proper safety gear of the time. 500 Hp stock seems conservative.