Re: Horsepower

Posted by Craig Hendrickson On 2011/1/5 11:44:58

I found an article in the March 1955 Hot Rod Magazine on the "then new" Pontiac V-8. It describes the engine testing procedure following the test code adopted recently by GM.

Fuel, oil and water pumps connected and operating.

Generator be rotated by the fan belt, but not charging.

No fan or air cleaner is used.

Carburetor heat is blocked off.

Stock exhaust manifolds used to carry exhaust into large capacity collectors.

Spark advance manually adjusted to produce maximum torque.

93 octane Research gasoline for Pontiac's 8.0:1 CR engine.

Dyno results mathematically corrected to 60F and 29.92in-HG [sea level atmospheric pressure].

For example, Pontiac's 287CID V-8 8.0:1CR engine produced 180HP at 4600rpm, 264 lb-ft at 2400 rpm.

As you might recall, Packard's then new 352CID V-8 8.5:1CR V-8 produced 260HP at 4600 rpm and 355 lb-ft at 2400 rpm. According to an article in HRM on August 1955, the same "GM test code" was followed.

To get the rear wheel horsepower, one can use the 1/4-mile drag test results from car magazines at the same time. A 1955 Packard Patrician which weighed 4800lb with driver and passenger ran the 1/4-mile drag at a trap speed of 78mph. This correlates to 178HP rear wheel. 178/260 is 0.685 or a reduction of 31.5% between gross and rear wheel net HP.

Driveline losses (converter, transmission, gears and tires) are usually considered to be about 15% of the difference between SAE net and RW HP. So, a reduction of about 16% would be a good number for gross to 1972 SAE net HP on a 1955 Packard Patrician.

Craig