MGB GT Engine
MGB GT Engine
All MGBs (except the V8 version) utilized the BMC B-Series engine. This engine was essentially an enlarged version of that used in the MGA with displacement being increased from 1622 cc to 1798 cc. The earlier cars used a three main bearing crankshaft, 18G-series.
In February 1964 positive crank-case breathing was introduced and engine prefix changed to 18GA, until October 1964, when a five-bearing crankshaft design was introduced, engine prefix became 18GB.
Horsepower was rated at 95net bhp on both 5 main bearing and earlier 3-bearing cars with peak power coming at 5400 rpm with a 6000 rpm redline. Torque output on the MGB had a peak of 110 lb·ft (150 N·m) Fuel consumption was around 25mpg.
US specification cars saw power fall in 1968 with the introduction of emission standards and the use of air or smog pumps. In 1971 UK spec cars still had 95 bhp (71 kW) at 5,500 rpm, with 105 lb·ft (142 N·m) torque at 2500 rpm.
Engine prefix became 18V and the SU carburettor needles were changed for reasons of the latest emission regulations, under ECE15.
By 1973 it was 94 bhp (70 kW); by 1974 it was 87, with 103 lb·ft (140 N·m) torque; by 1975 it was 85 with 100 lb·ft (140 N·m). Some California specification cars produced only around 70 hp (52 kW) by the late 1970s. The compression ratio was also reduced from 9 to 1 to 8:1 on US spec cars in 1972.