View Full Version : My Hawk's 40.6 Horsepower-HUH !!

05-23-2007, 08:28 PM
My manual gives the horsepower of the 289 engine as 40.6 horsepower.
Seems a bit low so how come the specification?? Blame the Brit's.
Back in the 40-60's the English goverment wanted to tax horsepower so the
Royal Auto Club (RAC) devised the formula below.
HP= square of cylinder diameter in inches multiplied by the number of cylinders divided
by 2.5. The 2.5 representing engine efficientcy of the times estimated at 40%.
For the Studebaker 289 with a bore of 3.56 inches, this computes to TA DA!! 40.6 horsepower, the number shown in my Hawk's manual.
Why Studebaker and other U.S companies adopted this almost meaninless rating
I have no idea, What's really funny is, to avoid a lot of tax, many British cars like
Jaguar built under square engines to heep the cylinder bore small and the
"taxable horsepower" low. Small bore -long stroke keeps the tax man away.
Now you know " the rest of the story"

Some day I'll tell you how James Watt, inventor of the steam engine, came up with the
current definition of horsepower as 33,000 foot -pounds /minute. Unbelievable!

...Dick Curtis

John Kirchhoff
05-23-2007, 10:18 PM
Back in the good old days, the license bureau (at least in Illinois) taxed the vehicle based upon the "taxable horsepower". It annoyed my dad that the tax on the 6 cylinder Lark was more than his V-8 Chevy.

05-24-2007, 12:08 AM
Interesting as the original Stude shop manual and Parts book (at least for E - 8E trucks) quotes the 40.6 HP rating for all Stude V8 engines (224, 259 & 289).

05-24-2007, 02:56 AM
That's correct! They all have the same BORE!! 3 9/16 in.[:0]

Studebakers Northwest
Ferndale, WA

05-24-2007, 09:42 AM
wow something i didnt know. its cool to learn these neat little facts.

Looking to build up my 62 lark daytona 289. any ideas?

Dwain G.
05-24-2007, 10:34 AM
I remember road tax based on 19.5 horsepower in all my parents Champions in Missouri. Can't remember exactly what the state called it, something like road horsepower, or taxable horsepower.

Dwain G.

05-24-2007, 04:25 PM
I wonder if the rationale was something like, "higher horsepower cars really tear up the road"!


1955 1/2 Ton Pickup
[i]The Red-Headed Amazon
Deep in the heart of Texas

05-24-2007, 04:27 PM
Well th; (I can call you that for short, right?) :D Just keep in mind that Mark's Studebaker Truck Chassis/Body Parts Catalog only mentions the years it covers.

In other words the 224 was the 1/2 year only, early 1955 car and '55-'56 Truck engine with the very short stroke crank, NOT the 232 engine used from 1951 to 1954.

It DID have a smaller bore and less taxable horsepower. So ALL Studebaker V-8's do not have the same bore, there also is the '64 Jet Thrust & Avanti R3 & R4 with 304.5 cu.in. It is .093 over the 289 bore.

quote:Originally posted by th12t33n

wow something i didnt know. its cool to learn these neat little facts.
Looking to build up my 62 lark daytona 289. any ideas?

Studebakers Northwest
Ferndale, WA