The Morris Isis name was first briefly used by the Morris Motor Company on a six-cylinder car made from 1929 to 1931. It was resurrected on a new six-cylinder midsize car from the British Motor Corporation in the 1950s to replace the Morris Six MS.
Morris Isis (1929–1935) and Twenty Five (1933–1935)
The Isis was a revised version of the 1927 Morris Six (JA series) and used the same 2468 cc engine and 3-speed gearbox. It had an all-new chassis, and the steel body had an American look, not surprising, as the body pressing dies from Budd were shared with some Dodge models.
It was the first Morris to have hydraulic brakes and chromium plating replaced the previous nickel finish on brightwork.
The car could exceed 65 mph (105 km/h) and return 28 miles per imperial gallon (10 L/100 km; 23 mpg-US).
After 3939 of the original Isis model had been made it received a facelift in 1932. The steel panel body was replaced by the traditional wood frame construction. Mechanically the car was similar but the transmission received a fourth speed. The chassis received additional cross bracing in 1934 and an automatic clutch and freewheel were fitted to some models. 3467 of the new Isis were made (including Twenty-Five models)
A de-luxe version, the Morris Twenty-Five was launched at the 1932 London Motor Show with larger 3485 cc engine.
Isis Series I (1955–1956)
The Series I Isis was launched in 1955 as a replacement for the Morris Six MS. It featured a six-cylinder engine, the 2.6 L (2639 cc/161 in³), 86 bhp C-Series unit from the Austin Westminster. Unlike the Westminster, the Isis had a single SU carburettor. The four-speed gearbox had a column change and was available with an optional Borg-Warner overdrive unit.
The car was based on the 4-cylinder Oxford Series II, sharing its almost-unibody shell and torsion beam front suspension. The bonnet was lengthened to accept the larger straight-6 engine, and a "woody" 2-door estate version was a novelty. With the strong engine, the Isis could reach 90 mph (145 km/h).
Unlike its sister car the Austin Westminster, which enjoyed moderate success against the volume-selling Ford and Vauxhall sixes of the time, sales were poor, with just 8,500 sold.
Isis Series II (1956–1958)
The Morris Isis Series II was based on the Morris Oxford Series III body but with longer bonnet to accommodate the 6-cylinder engine.
In line with changes to the corresponding Oxford line, BMC redesigned the Isis for 1956 with updated styling including a more elaborate mesh grille, chrome side strips and small fins. The engine power increased to 90 bhp. An automatic transmission option was also added. The manual version had a four-speed box operated by a short gearstick located on the right-hand side of the front bench seat. The handbrake lever was located just behind the gearstick. Sales remained weak, and the line ended in 1958.
A de luxe saloon with overdrive tested by the British magazine The Motor in 1956 had a top speed of 90 mph (140 km/h) and could accelerate from 0-60 mph (97 km/h) in 17.6 seconds. A fuel consumption of 26.2 miles per imperial gallon (10.8 L/100 km; 21.8 mpg-US) was recorded. The test car cost £1025 including taxes. The overdrive unit had added £63 to the price.