Year of detuning?
Thread Starter
Racer
Joined: Aug 2014
Posts: 448
Likes: 42
Year of detuning?
What year was the 454 de-tuned? It seems like the 1971 454 had all it's ***** intact and in 1972 some castration crept in. If that's the case, what was done to the engine to kill the power?
Racer
Joined: May 2008
Posts: 422
Likes: 6
From: Boca Raton Florida
AL Gore, I mean Ralph Nader, emmission controls, and insurance regulation. Gas prices, and lead fuel started being phased out and compression dropped and the engineers were pushed into fuel economy mode, the end of the era. Smog pumps, yada yada. Then cats, and then you have 185 hp small blocks.
Le Mans Master
Joined: Aug 2008
Posts: 5,578
Likes: 61
From: Austin TX
AL Gore, I mean Ralph Nader, emmission controls, and insurance regulation. Gas prices, and lead fuel started being phased out and compression dropped and the engineers were pushed into fuel economy mode, the end of the era. Smog pumps, yada yada. Then cats, and then you have 185 hp small blocks.
Melting Slicks
Joined: Nov 2004
Posts: 2,672
Likes: 6
From: Nevada City California
It was 1972. The horsepower ratings for the LS-5 was 350hp gross and 270 hp net. In 1971, the LS-5 was 365hp gross and a net rating of 285hp. The difference in the two years came about because of additional carburation, distributor and timing adjustments.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The big 'drop' in '72 was because of the change in power rating system from SAE Gross to SAE Net. There was actually very little change in actual performance from '71 to '72.
The major power change year (for GM) was 1971. That's when every engine was de-tuned so that they could run on unleaded 'regular' fuel. The engine compression was reduced across the board and several changes were made to heads, cam, etc.
That doesn't mean that the powerplants were neutered. The engines still had a decent amount of power. Also, some of them were specified at lower RPM numbers than they could actually attain (due to absurd insurance company rates for high-perf cars). Performance was significantly lower than in 1970...but still better than the anemic cars of the mid-late 70's.
The major power change year (for GM) was 1971. That's when every engine was de-tuned so that they could run on unleaded 'regular' fuel. The engine compression was reduced across the board and several changes were made to heads, cam, etc.
That doesn't mean that the powerplants were neutered. The engines still had a decent amount of power. Also, some of them were specified at lower RPM numbers than they could actually attain (due to absurd insurance company rates for high-perf cars). Performance was significantly lower than in 1970...but still better than the anemic cars of the mid-late 70's.
Last edited by 7T1vette; Sep 7, 2014 at 02:53 PM.
Melting Slicks
Joined: Jul 2009
Posts: 2,091
Likes: 40
Which are all simple fixes.
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