MGB 18G/18GA Distributor Advance Curves & Increased-Capacity Oil Sump - Manual p456

This is page 456 from an MG workshop manual section titled 'Other Special Items,' covering competition/tuning modifications. The page contains two figures. Fig. 4 presents distributor advance curves plotting distributor advance in degrees (0–12+) against distributor revolutions per minute (0–4000+). Two curves are shown: a Competition distributor (Serial No. 40943, BMC Part No. C-BHA 4415) which reaches about 12 degrees advance at roughly 3000 distributor RPM, and a Standard distributor (Serial No. 40897, BMC Part No. 12H 792) which reaches about 10 degrees advance more quickly at lower RPM. Fig. 5 shows fabrication details for an increased-capacity oil sump, applicable to 18G/18GA engines only. It includes Section X-X, Section Y-Y, and a plan view. Key details: the bottom of the sump is cut off at 'Line A' and an additional 1-inch section is welded in to give the depth shown (overall depth dimensions of 2 1/4 in. and 5 25/32 in. are given), and a baffle is spot-welded in position (baffle plate details referenced to Fig. 6). Readers can learn distributor advance characteristics for standard versus competition distributors and how to modify a sump for increased oil capacity.