273/4 -318 debate
Were having a discussion on the merits of the 273-4 engine compared to the 318-2 of the following years, sometimes even the same year. Sure the 273-4 was a hot motor back in 65 when it was the best thing between the fenders of the early A's but you just can't deny that a 20% larger motor is going to make a difference. Performance test are all over the board, depending if the dufus can drive or if the dyno is set up properly, yadda yadda...but I found a site that has a lot of info on cars in general and has generated graphs (from factory data) on performance specs. So I tried to match 2 like cars (in weight, gear and transmissions) with our 273-4 and the 'new' 318-2. Results? Well, I think it would ultimately come down to the reaction time between these 2 motors as they are pretty close. You can see the shift points are higher on the smaller higher winding 273 and the torque advantage goes to the 318 down low. Theoretical top speed goes to the high winding 273 due to the cam profile and possible higher RPM potential of its heavier valve springs and forged crank.
1965 273-4 Barracuda
reference weights: shipping weight 3029 lbs base curb weight: test weight 1430 kg / 3152 lbs
how fast is this car ? top speed: 126 mph (©theoretical);
accelerations: 0- 60 mph 6.9© s; 0- 100 km/h 7.3© s (simulation ©automobile-catalog.com); 1/4 mile drag time (402 m) 15.6
1968 318-2 Barracuda
reference weights: shipping weight 1363 kg / 3005 lbs base curb weight: 1430 kg / 3152 lbs
how fast is this car ? top speed: 178 km/h (111 mph) (©theoretical);
accelerations: 0- 60 mph 6.8© s; 0- 100 km/h 7.3© s (simulation ©automobile-catalog.com); 1/4 mile drag time (402 m) 15.4© s
overlaid
<<<lower 75 from tq curve points to align 5250rpm intersection>>>
<<<the tq graph should start at 100 so the data points align SAE>>>
and the overlay of the HP/torque curves from factory data. increased displacement really shows in the torque curve but the smaller 273 can hold its HP peak longer. This is due to camshaft differences. Put a similar cam in a 318 and its curve would change.
Bottom line: in a 1/4 mile race all things being somewhat stock on these 2 cars, the 318 would edge it by .2 seconds..theoretically. Now on the highway having some fun with your buddy, the 273 would probably walk away after 4500 RPM. Now put the 4bbl cam in the 318 and it would probably be a 20% increase across the board on the 318 data. To say the 273-4 would walk a 318-2 in a drag race is not supported in this data. All data is from blueprint specs and we all know how well those are kept in production, especially compression ratios.
Food for thought...or to fling?
Were having a discussion on the merits of the 273-4 engine compared to the 318-2 of the following years, sometimes even the same year. Sure the 273-4 was a hot motor back in 65 when it was the best thing between the fenders of the early A's but you just can't deny that a 20% larger motor is going to make a difference. Performance test are all over the board, depending if the dufus can drive or if the dyno is set up properly, yadda yadda...but I found a site that has a lot of info on cars in general and has generated graphs (from factory data) on performance specs. So I tried to match 2 like cars (in weight, gear and transmissions) with our 273-4 and the 'new' 318-2. Results? Well, I think it would ultimately come down to the reaction time between these 2 motors as they are pretty close. You can see the shift points are higher on the smaller higher winding 273 and the torque advantage goes to the 318 down low. Theoretical top speed goes to the high winding 273 due to the cam profile and possible higher RPM potential of its heavier valve springs and forged crank.
1965 273-4 Barracuda
reference weights: shipping weight 3029 lbs base curb weight: test weight 1430 kg / 3152 lbs
how fast is this car ? top speed: 126 mph (©theoretical);
accelerations: 0- 60 mph 6.9© s; 0- 100 km/h 7.3© s (simulation ©automobile-catalog.com); 1/4 mile drag time (402 m) 15.6
1968 318-2 Barracuda
reference weights: shipping weight 1363 kg / 3005 lbs base curb weight: 1430 kg / 3152 lbs
how fast is this car ? top speed: 178 km/h (111 mph) (©theoretical);
accelerations: 0- 60 mph 6.8© s; 0- 100 km/h 7.3© s (simulation ©automobile-catalog.com); 1/4 mile drag time (402 m) 15.4© s
overlaid
<<<lower 75 from tq curve points to align 5250rpm intersection>>>
<<<the tq graph should start at 100 so the data points align SAE>>>
and the overlay of the HP/torque curves from factory data. increased displacement really shows in the torque curve but the smaller 273 can hold its HP peak longer. This is due to camshaft differences. Put a similar cam in a 318 and its curve would change.
Bottom line: in a 1/4 mile race all things being somewhat stock on these 2 cars, the 318 would edge it by .2 seconds..theoretically. Now on the highway having some fun with your buddy, the 273 would probably walk away after 4500 RPM. Now put the 4bbl cam in the 318 and it would probably be a 20% increase across the board on the 318 data. To say the 273-4 would walk a 318-2 in a drag race is not supported in this data. All data is from blueprint specs and we all know how well those are kept in production, especially compression ratios.
Food for thought...or to fling?
