Standards for measuring horsepower: 1969 427 compared to 1972 454?
08-11-2013, 03:25 PM
#1
Standards for measuring horsepower: 1969 427 compared to 1972 454?
In 1972 454 cubic inch big block motor was rated at 270 hp.
In 1969 427 big block was rated at 390 hp.
http://web-cars.com/corvette/1972.php
From the link above, I found out that standards for measuring horsepower came into effect in 1972 and that's why the lower hp numbers.
Can any of you tell me how much horsepower the 1969 427 or 350 engines have by todays hp standards?
In 1969 427 was rated at 390 hp as mentioned above and 350 small block was rated at 350 hp. But measuring the hp by todays standards, those hp numbers are lower.
In 1969 427 big block was rated at 390 hp.
http://web-cars.com/corvette/1972.php
From the link above, I found out that standards for measuring horsepower came into effect in 1972 and that's why the lower hp numbers.
Can any of you tell me how much horsepower the 1969 427 or 350 engines have by todays hp standards?
In 1969 427 was rated at 390 hp as mentioned above and 350 small block was rated at 350 hp. But measuring the hp by todays standards, those hp numbers are lower.
08-11-2013, 05:56 PM
#3
From my understanding, and put very simply....
The old way was called "Brake HP" and was measured directly from the motor on a stand.
The new way is called " Rear wheel HP" which is just what it sounds like. The HP measured at the rear wheels with all the HP robbing drive train components in the mix.
In reality the way they calculate HP numbers were probably changed to help with the new government regulations, even though for a couple years they were the same engine.
The old way was called "Brake HP" and was measured directly from the motor on a stand.
The new way is called " Rear wheel HP" which is just what it sounds like. The HP measured at the rear wheels with all the HP robbing drive train components in the mix.
In reality the way they calculate HP numbers were probably changed to help with the new government regulations, even though for a couple years they were the same engine.
08-11-2013, 06:30 PM
#4
Race Director
From my understanding, and put very simply....
The old way was called "Brake HP" and was measured directly from the motor on a stand.
The new way is called " Rear wheel HP" which is just what it sounds like. The HP measured at the rear wheels with all the HP robbing drive train components in the mix.
The old way was called "Brake HP" and was measured directly from the motor on a stand.
The new way is called " Rear wheel HP" which is just what it sounds like. The HP measured at the rear wheels with all the HP robbing drive train components in the mix.
Old standard was SAE Gross. It was very lenient (unrealistic) as far as inlet air temp and humidity. It also allowed open headers, recurved distributor and running with no accessories.
New standard is SAE Net. Realistic air temp & humidity. Full exhaust as installed in vehicle including mufflers. Accessories such as water pump is hooked up. Distributor & carb/injection & air cleaner as installed in vehicle.
SAE Net is not rear wheel power.
1971 GM cars give you a real good idea of how the ratings compare as the engines were rated both ways. The '71 Corvette LS5 was 360 hp gross, 285 hp net.
Extrapolating a bit, the '69 427/390 would be ~310 net hp. The '72 454/270 would be ~340 gross hp. Something along those lines at least.
08-11-2013, 06:48 PM
#5
Nope.
Old standard was SAE Gross. It was very lenient (unrealistic) as far as inlet air temp and humidity. It also allowed open headers, recurved distributor and running with no accessories.
New standard is SAE Net. Realistic air temp & humidity. Full exhaust as installed in vehicle including mufflers. Accessories such as water pump is hooked up. Distributor & carb/injection & air cleaner as installed in vehicle.
SAE Net is not rear wheel power.
1971 GM cars give you a real good idea of how the ratings compare as the engines were rated both ways. The '71 Corvette LS5 was 360 hp gross, 285 hp net.
Extrapolating a bit, the '69 427/390 would be ~310 net hp. The '72 454/270 would be ~340 gross hp. Something along those lines at least.
Old standard was SAE Gross. It was very lenient (unrealistic) as far as inlet air temp and humidity. It also allowed open headers, recurved distributor and running with no accessories.
New standard is SAE Net. Realistic air temp & humidity. Full exhaust as installed in vehicle including mufflers. Accessories such as water pump is hooked up. Distributor & carb/injection & air cleaner as installed in vehicle.
SAE Net is not rear wheel power.
1971 GM cars give you a real good idea of how the ratings compare as the engines were rated both ways. The '71 Corvette LS5 was 360 hp gross, 285 hp net.
Extrapolating a bit, the '69 427/390 would be ~310 net hp. The '72 454/270 would be ~340 gross hp. Something along those lines at least.
both SAE Gross and Net are 'brake' horsepower- the engines were tested on a stand with the flywheel output fed into a 'brake' or dyno.
08-11-2013, 09:14 PM
#7
Race Director
From my understanding, and put very simply....
The old way was called "Brake HP" and was measured directly from the motor on a stand.
The new way is called " Rear wheel HP" which is just what it sounds like. The HP measured at the rear wheels with all the HP robbing drive train components in the mix.
In reality the way they calculate HP numbers were probably changed to help with the new government regulations, even though for a couple years they were the same engine.
The old way was called "Brake HP" and was measured directly from the motor on a stand.
The new way is called " Rear wheel HP" which is just what it sounds like. The HP measured at the rear wheels with all the HP robbing drive train components in the mix.
In reality the way they calculate HP numbers were probably changed to help with the new government regulations, even though for a couple years they were the same engine.
08-11-2013, 09:26 PM
#8
