View Full Version : Nailhead factory HP/Torque ratings

09-15-2010, 06:07 PM
I've read a bunch of old threads in this forum and at V8buick.com where alot of you guys have dynoed your engines. My question comes from your HP & torque numbers. My '64 service manual 'claims' 325 HP and 445 torque for a 401 and 340 HP and 465 torque for a 425. Is the factory manual incorrect? If yes, then what was up with that in 1964?:confused:

Ted Nagel
09-19-2010, 09:29 AM
I used a HP calculator from another website -inputs are

weight and 1/4 mile MPH. The #s are from a Car Life article on a '64 Wildcat. Engine was a 2x4 bbl 425. manual trans.



weight = 4420 pound = 4420 pound velocity = 87 mile/hour = 87 mile/hour

horsepower (hp) = 227.16 horsepower

Same calculation for a 64 Electra that Car Life tested - it had an automatic.


weight = 4265 pound = 4265 pound velocity = 80 mile/hour = 80 mile/hour

horsepower (hp) = 170.42 horsepower

So...the marketing guys had more say over the HP listed than the engineers IMHO. They were not alone! All the mfers were pumping up their ##s.

Ted Nagel
09-19-2010, 09:40 AM
http://www.ajdesigner.com/phphorsepower/horsepower_equation_trap_speed_method_horsepower.p hp

09-19-2010, 07:23 PM
Those are ratings at the wheels, correct?

bob k. mando
09-19-2010, 08:47 PM
Ted's conversions would necessarily be "drive wheel horsepower".

it's important to remember that the 'Gross Horsepower' rating system used up until 1972 didn't even include the transmission, it was taken straight from the flywheel.

09-19-2010, 10:42 PM
Also no belt driven accessories and special "Dyno Room" exhaust systems.

09-20-2010, 10:33 AM
Here's a short article:


And to help the bench racing:


10-14-2010, 12:23 PM
My results tell me THEY WERE BIG FAT LIARS!

By my experience on the dyno, there's no way a stock engine can actually achieve the factory rated HP & torque numbers at the flywheel with no accessories and bare stock manifolds.

I agree that their marketing dept. probably had more to do with the numbers- THEORETICAL NUMBERS that sounded good, and they ran with it. This seems to be a re-occuring theme amogst all the engine manufacturers of the era.a


Ted Nagel
10-14-2010, 01:04 PM
I think I just bought a stroker kit for a nailhead.
Have to make another trip to the dyno soon :car: