Transmission ratio makes BB = SB?

[Finnerty]

Planning for an eventual repower and wanting to go SBC to replace BBC (stay calm):

If a BBC 330 HP cruises at 3200 rpm peak TQ 420 with a 1.99 ratio that's 835.6 Prop TQ
If a SBC 330 HP cruises at 3200 rpm peak TQ 370 with a 2.47 ratio that's 913.9 Prop TQ

Why not go with a small block?

 

[Bondo]

Ayuh,.... The torque curves are very different, 'n the SBC spins up to 5000 or 5200 to make that horsepower, where the BBC spins the horsepower at 4600 or so,....

My guess is, the SBC will struggle badly tryin' to get on plane,...
Unless ya change yer transmission gear ratio,...

 

[Chris1956]

Torque is not the same between the SBC and the BBC. Those 24 - 26 footers need the torque of the BBC to make them tolerable (IMO).

If you have a cruiser, stick with the BBC.

 

[Maclin]

Much lower MPH between those 2 ratios at same rpm, For example, at WOT and top rpm of 4.8k the MPH difference could be almost 10 mph.

 

[Silvertip]

You are ignoring prop RPM. Cruise speeds will not be the same with different gear ratios. Compensate with different prop and you have an absolute dog for hole shot.