RapidRuss said:

Yes with the early 460's that were in the cars..where they started life before making it to trucks...the early 460 had slighlt larger port heads and Intakes, Higher CR pistons, and a short deck height of 10.300 VS the later 10.322" deck height...

A few of the earlier 429CJ models were underrated @ 370hp..

I hope this helps shed some light on what you were asking !

~Russ

Click to expand...

Mil1ion said:

At the back of the crank vs now at the rear wheels

Click to expand...

Mil1ion said:

Don't forget ....Horsepower was rated differently back then as well.

At the back of the crank vs now at the rear wheels

Click to expand...

john112deere said:

You sure about that? I'm no expert, but I believe most car manufacturers still list power at the crank in their literature.

Click to expand...

SAE gross horsepower

Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower (bhp), frequently referred to as SAE gross horsepower because it was measured in accord with the protocols defined in SAE standards J245 and J1995. As with other brake horsepower test protocols, SAE gross hp was measured using a blueprinted test engine running on a stand with no belt-driven accessories, air cleaner, mufflers, or emission control devices and sometimes fitted with long tube "test headers" in lieu of the OEM exhaust manifolds.[citation needed] The atmospheric correction standards for barometric pressure, humidity and temperature were relatively idealistic. The resulting gross power and torque figures therefore reflected a maximum, theoretical value and not the power of an installed engine in a street car. Gross horsepower figures were also subject to considerable adjustment by the manufacturer's advertising and marketing staff under the direction of product managers.[citation needed] The power ratings of mass-market engines were often exaggerated beyond their actual gross output, while those of the highest-performance muscle car engines often tended to be closer in actual output to their advertised, gross ratings.[citation needed]

No pre-1972 engine in its unaltered, production line stock form, as installed in the vehicle, has ever yielded documented, qualified third party validated power figures that equal or exceed its original gross rating.[citation needed] Claims that such engines were "under-rated" are therefore dubious; for example, the 1969 427 ZL1 Chevrolet, rated at 430 bhp (320.7 kW), is frequently cited[who?] as an "under-rated" high performance engine, yet it produced only 376 horsepower (280 kW).

Click to expand...

SAE net horsepower

In the United States the term "bhp" fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net hp testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold. The change to net hp effectively deflated power ratings to assuage the auto insurance industry and environmental and safety lobbies.

Click to expand...

Mil1ion said:

Don't forget ....Horsepower was rated differently back then as well.

At the back of the crank vs now at the rear wheels

Click to expand...