Pontiac 2+2
1965-67

Model year
Engine name
Displacement
Carburetor series (bbl)
Output @ rpm
Torque @ rpm
1965-66
2+2 V8
421 cu in (6.9 L)
Carter C4-AFB (4)
338 hp (252 kW; 343 PS) @ 4600
459 lb⋅ft (622 N⋅m) @ 2800
1965-66
2+2 V8
421 cu in (6.9 L)
Rochester 2-G (2) x3
356 hp (265 kW; 361 PS) @ 4800
459 lb⋅ft (622 N⋅m) @ 3200
1965-66
2+2 HO V8
421 cu in (6.9 L)
Rochester 2-G (2) x3
376 hp (280 kW; 381 PS) @ 5000
461 lb⋅ft (625 N⋅m) @ 3600
1967
2+2 V8
428 cu in (7.0 L)
Rochester Q-Jet (4)
360 hp (268 kW; 365 PS) @ 4600
472 lb⋅ft (640 N⋅m) @ 2800
1967
2+2 HO V8
428 cu in (7.0 L)
Rochester Q-Jet (4)
376 hp (280 kW; 381 PS) @ 5100
465 lb⋅ft (630 N⋅m)

Question: When was the V8 displacement bumped up to the 428 cu ?
Answer: In 1965, the V8 displacement was 421 cu in (6.9 L) and was bumped up to the 428 cu in 1967.