The MGB GT V8 had a 12-volt negative earth system just like the four-cylinder MGB, most parts originally supplied by Lucas but later sourced elsewhere. Originally, two single-fill, 11 plate 6-volt batteries were supplied, but from the start of “rubber bumper” MGB production in 1974, a single 12-volt battery with new battery box was fitted. The V8 used an AC Delco alternator of part number 7982707 and higher 46 amp output. Starter motors were supplied by Lucas, type 3M100 and were typically painted to match the engine colour.
The remainder of the electrical system was very much the same as the same age of four cylinder MGB GT including all lights, although the four cylinder cars optional higher rated sealed beam headlamps were standard.
Where the V8 did show an obvious visual difference was in the use of 80mm diameter speedo and tachometer because of the bulkier collapsible steering columns didn’t allow the original 4” (102mm) instruments to fit. The tacho was obviously calibrated for an 8 cylinder engine rather than 4 and the speedo was calibrated to 140mph rather than 120mph.
The subordinate dual gauge (oil pressure/coolant temp) were the same 52mm size as four-cylinder models, but the oil pressure gauge was recalibrated 0 to 60psi, rather than 0 to 100psi in deference to the normal V8 oil pressure that generally only reaches just over 40psi whereas the four-cylinder engines ran at 65 to 70psi. The recalibration meant that the needle would sit in much the same position as on the four-cylinder gauge, simply to ‘look right’ to customers trading up from the four-cylinder cars and to avoid their worries about such a ‘low oil pressure’.
In addition to the V8 specific gauges the indicator and wiper stalks introduced a new format with the overdrive now being switched from the wiper stalk.