Dale. To expand a bit on what Slumlord stated about 292 vs. 312 performance...
The '57 vintage 'C' code 292s and 'D' code 312s are equipped VERY similarly.
- the cylinder heads used on the '57 'Birds all had large casting letter ECZ-Gs for the C, D, and E code engines; they used the same valve porting, valve sizes and combustion chamber shapes and volumes. The difference in static compression ratio between the 292 and the 312 was only due to the difference in cylinder displacement.
- the camshafts for the C code 292, D code 312, and standard offering 312 E, and F code engines (both passenger car and 'Bird) were identical in valve lift, lift duration, valve overlap, cam lobe center angle, and valve event timing.
- the rocker arm ratios for all C, D, E, and F code engines (both passenger car and 'Bird) were identical.
- the exhaust manifolds were the same for all C, D, E, and F code 'Birds.
The performance difference between the 'C' code 292 and the 'D' code 312 was derived from the 312 having a larger cylinder bore, longer piston stroke, higher static compression ratio (due to increased cylinder displacement), and a four barrel carburetor.
The olde school way of explaining all of this was, 'There's NO substitute for cubic inches!'
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York