1971-1973 MGB Service Manual p39 - Transmission, Steering & General Data Specs
MGB workshop page covering gearbox/overdrive oil checking, draining, filling and relief-valve service plus a General Data column with engine, ignition, fuel and gearbox/overdrive specifications.
This is page 39 of an MGB service/maintenance manual covering three sections: Transmission, Steering/Suspension, and General Data. The Transmission section explains checking gearbox oil via the combined filler/dipstick under the carpet by the control console, draining the gearbox and overdrive unit, cleaning the sump filter and its magnets, servicing the relief valve filter, and refilling (with a warning that anti-friction additives must not be used). It also covers rear axle oil level checking and propeller shaft sliding-yoke lubrication. The Steering/Suspension section describes front wheel toe-in (distance 'A' must be 1/16 to 3/32 in. less than 'B') and periodic greasing of the three lubricating nipples on each swivel pin. The General Data section lists specifications for the 1798 c.c. 18V engine and early 18GK/18GJ/18GH/18GF variants: bore, stroke, compression ratio (8:1), firing order (1,3,4,2), valve clearance, oil pressures, idle speeds; ignition timing for 1971-1972 and 1973 (Champion N-9Y plugs, .025 in. gap, .014-.016 in. points gap); fuel system data including S.U. HIF4/HS4 carburetters, needle types, and the S.U. AUF 300 electric pump; and gearbox/overdrive ratios with top gear speeds per 1,000 r.p.m. Readers can find tune-up specs, lubrication procedures, and drivetrain ratios here.
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Frequently asked questions
- What is the ignition timing for the 1971-1972 MGB 18V engine?
- 16° B.T.D.C. at 1,500 r.p.m. (18GK is 15° B.T.D.C. at 1,500 r.p.m.; 18GJ, 18GH and 18GF are 20° B.T.D.C. at 1,000 r.p.m.). For 1973, timing is 11° B.T.D.C. at 1,500 r.p.m. with vacuum disconnected.
- What spark plugs and gap does the MGB use?
- Champion N-9Y sparking plugs with a plug gap of .025 in. (.64 mm.); the contact breaker gap is .014 to .016 in. (.36 to .41 mm.).
- What carburetters and fuel pump are fitted?
- 1971-1972: 18V uses two S.U. type HIF4 carburetters; 18GK, 18GH, 18GF use two S.U. type HS4. 1973 cars use two S.U. HIF 4 with ABD needles and an S.U. type AUF 300 electric fuel pump.
- How do I check the MGB gearbox oil level?
- Lift the carpet on the right-hand side of the gearbox cover at the rear of the control console, remove the rubber plug, clean around the dipstick before removing it, and maintain the oil level at the 'HIGH' mark. Do not use anti-friction additives in the gearbox or overdrive.
- What are the MGB overdrive gear ratios?
- Overdrive ratio is .82:1. Overall ratios: First 13.446:1, Second 8.47:1, Third 5.40:1 (4.43:1 in overdrive), Fourth 3.909:1 (3.20:1 in overdrive), Reverse 12.098:1. Top gear speed per 1,000 r.p.m. is 18 m.p.h. standard, 22 m.p.h. overdrive.
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