Roush vs 427FE vs Keith Craft

[CobraEd]

Originally Posted by AL427SBF

Might as well jump into the fray, and generalities do apply because on balance they apply to most engines.

It takes more energy to spin up a BB's rotating mass versus SB rotating mass because the SB has less mass to spin up, basic physics. That energy comes from your motor and is stored as kinetic energy in the rotating assembly.

The BB guys do better at the 1/4 mile because they can rev it up, dump the clutch - and use all that kinetic energy stored in the rotating assembly for a good launch and let the BB HP do the rest.

The SB guys do better on road courses because it's accelerate & brake driving, less rotating mass to slow down and speed up means the SB can stop and go faster as well as corner better*.

Yeah the BB makes more power earlier in the RPM range, but the SB revs faster than the BB (and typically revs higher than the BB). Hypothetically, if one were to stomp it at say 3000 RPM in some gear, if it takes the BB 2 seconds to get to ~5000 RPM, then those 2 seconds will put the SB at ~6000 RPM ( again hypothetical). In other words, both would be at or near their respective peak horse power levels in the same amount of time.

*That can be debated later, but real road course men prefer SBs

AL427SBF gets it. It is not about how high an engine can rev, it is about how fast an engine can rev. And of course you can build a 385 series that can rev faster than a SBF, but the statement assumes all things being roughly equal. Apples to apples. Dynos only show torque and HP (a derivitive of torque) They cannot and do not show how quickly an engine can rev. This is not about selecting parts and assembling engines. It is about internal combustion physics. AL427SBF gets it 100% completely. He is correct.


.