48mm vs. 58mm TB on relatively stock LT1 thread from the LT1/LT4 Tech board at Project TransAM.

 

the fact that this gentlemen lost so little hp and no torque on a virtually stock engine should clear up some confusion on that issue.

i personally gained 2 tenths in the quarter with the swap i mentioned at the beginning of this thread. this was when the 355 was making 374 hp at the rear wheels. with the cam, head work and a few tweaks we were putting down over 460 at the rear wheels. would have been interesting to see what the 48mm tb would have cost at that output. i'd guess 15 hp at peak and a bit more torque. same is true of carbs to an extent.

JB