SBF or BBF?

[olddog]

I'll give you another perspective as to what you want for an engine. Engines that make a lot of high rpm hp generally do not make good torque at low rpm, and the torque line looks like a drawing of a mountain. Engines that make good low rpm torque generally quit breathing at higher rpm, however they generally have a flat torque line from off idle up to midrange rpms before dropping off like a rock.

fictional engine #1 = low rpm torque monster.
RPM Torque HP
1500 450 129
2000 490 187
2500 500 238
3000 500 286
3500 500 333
4000 500 381
4500 500 428
5000 470 447
5500 430 450
6000 390 446

Fictional engine #2 high rpm hp monster
RPM Torque HP
1500 220 63
2000 250 95
2500 280 133
3000 300 171
3500 310 207
4000 320 244
4500 330 283
5000 340 324
5500 350 367
6000 360 411
6500 370 458
7000 370 493
7500 350 500
8000 320 487

You will note torque monster is all in at 5500 rpm and 450 hp, while hp monster is making 500 hp at 7500 rpm. Even though hp monster is making 50 hp more its peak torque is only 370 ft lb, while torque monster is making 500 ft lb from 2500 to 4500 rpm and doesn't drop off to 370 ft lb until well above its peak hp.

Now if you keep hp monster in the 7000 to 8000 rpm range he will beat the pants off of torque monster every time (assuming proper gearing in both cases). However at 6000 rpm and bellow, torque monster will eat hp monsters lunch. For example at 5000 rpm torque monster is making 447 hp while hp monster is only making 367 hp.

Also torque monster will give you the same torque (throttle responce) at practically any rpm bellow 6000, while hp monster's torque is different at every rpm, making throttle responce so unpredictable it can take the fun out of driving.

So ask yourself, how many rpm do I want to turn and how often will I have it there. Remember, the clutch is mighty close to your legs in these cars!

Paste these two charts into a spread sheet program and graph them. You will be impressed with the results.