23-05-2022, 12:22 AM
It would appear to be a 1" OM carb, the body number 617 being fitted as a pair of carbs on MG's from the 1932 12hp 6 cyl, 1933 850cc J2 4 cyl, 1934 to 1936 P & P.B. 8hp 4 cyl and as a triple carb set on the 1933 K.A. & K.B. 12hp 6cyl. On none of these applications was a piston spring ever fitted. Some had a weighted brass piston and some a weighted zinc piston. Recommended needles varied widely between the four MG models, so best to wait for someone on here who's using an OM carb on their A7 to recommend a needle.