which is true???
Thread Starter
Racer
Joined: Aug 2009
Posts: 294
Likes: 5
From: Caledonia Ms
which is true???
the '72 454 mota is rated at a lowly 270hp. i have been told 2 different stories as to why this mota is rated this low. the first one of course is the "emission reason". the other story is that the '72 mota is exactly the same as the '71 454 is just that GM had rated the '71 mota without all the accessories attached to it, like AC, power steering, alternator, water pump, etc. and the '72 motor is rated with all the accessories thus giving a lower hp number. which one of these stories is fact? thanks matt
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
There was a thing back then about HP ratings- Either "NET" or "SAE". One was in an as installed condition and the other was a bare engine. And the emmission thing is correct too. Compression was less, gas was turning to garbage, unleaded fuels, EGR, long list of stuff.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
The SAE rating factor changed in '72 to net horsepower, so part two is correct. But number one is correct if comparing 1970 to 1971 power. The primary issue was the drop in compression for the engines to run on low-lead gas.
So it depends on how the question is phrased. In the context you used it in, both would be correct.
So it depends on how the question is phrased. In the context you used it in, both would be correct.
Le Mans Master
Joined: Oct 2007
Posts: 7,442
Likes: 965
From: Tennessee/Rhode Island
Responses above are correct: SAE gross HP ratings prior to 1972 were the HP of the engine at the flywheel with zero accessories (no A/C, alternator, PS pump, probably no fan, no exhaust system) versus Net HP is everthing hooked up to the motor (as installed). The HP numbers of the late sixties and early 70's motors are not nearly as great a difference as the later smog motors when you factor in the SAE gross HP method versus the change in 1972 to Net HP ratings. For example, a 330HP LT-1 rated with the SAE method really does not have that much more HP than a 1974 L-82 rated at 250HP Net.
Last edited by jb78L-82; Sep 2, 2009 at 01:14 PM.
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
The SAE rating factor changed in '72 to net horsepower, so part two is correct. But number one is correct if comparing 1970 to 1971 power. The primary issue was the drop in compression for the engines to run on low-lead gas.
So it depends on how the question is phrased. In the context you used it in, both would be correct.
So it depends on how the question is phrased. In the context you used it in, both would be correct.
Le Mans Master
Joined: Jun 2005
Posts: 5,447
Likes: 3
From: Syracuse NY
the '72 454 mota is rated at a lowly 270hp. i have been told 2 different stories as to why this mota is rated this low. the first one of course is the "emission reason". the other story is that the '72 mota is exactly the same as the '71 454 is just that GM had rated the '71 mota without all the accessories attached to it, like AC, power steering, alternator, water pump, etc. and the '72 motor is rated with all the accessories thus giving a lower hp number. which one of these stories is fact? thanks matt
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