Pontiac 121ci Engine Specs

Bore, stroke, displacement and compression for all 4 Pontiac 121ci engines, compared side by side. Plus rod ratio and head specs where published.

At a glance

Displacement	121 ci
Cylinders	4
Bore	3.386–3.500"
Stroke	3.150–3.386"
Compression	8.0–9.0:1
Advertised power	96–165 hp
Years	1985–1994

Engines in this family

Engine	Displacement	Bore × Stroke	CR	HP
LT3	121 ci	3.3858" × 3.3858"	8:1	165
LQ5	121 ci	3.5" × 3.15"	9:1	—
LT2	121 ci	3.3858" × 3.3858"	8.8:1	96
LE4	121 ci	3.3858" × 3.3858"	—	110

Factory cars with a Pontiac 121ci

• Pontiac Sunbird: 1985, LQ5; 1986, LQ5; 1987, LT2, 96 hp; 1987, LT3, 165 hp; 1988, LT2, 96 hp; 1988, LT3, 165 hp; 1989, LT2, 96 hp; 1989, LT3, 165 hp; 1990, LT2, 96 hp; 1990, LT3, 165 hp; 1991, LT2, 96 hp; 1992, LE4, 110 hp; 1993, LE4, 110 hp; 1994, LE4, 110 hp
• Pontiac Grand Am: 1987, LT3, 165 hp; 1988, LT3, 165 hp; 1989, LT3, 165 hp

What varies across the family

Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.

1 of 4 are oversquare — bore larger than stroke, which favours revs over low-end torque.

Each engine page carries rod ratio, mean piston speed, bore/stroke character and cylinder head specs where published, and links into the calculators with its dimensions already filled in.

← All Pontiac engines