Correct lubrication is fundamental to the longevity and reliability of the MGB engine, and using the right products, both during routine maintenance and during an engine rebuild, makes a measurable difference to component life and performance. The B-series engine was designed around the lubricants available in the 1960s and 1970s, and a mineral-based 20W/50 engine oil remains the most widely recommended specification for standard and mildly modified engines. Classic-specification oils are formulated with the additive packages and viscosity characteristics suited to the wider tolerances, flat tappet camshafts, and plain bearings found in engines of this era, modern fully synthetic oils designed for tight-tolerance modern engines are generally not recommended, as they can cause oil leaks past seals and gaskets not designed for thinner viscosities, and may not contain sufficient zinc and phosphorus additive to protect the camshaft and followers. SU carburettor damper oil is required for topping up the dashpot dampers in each carburettor.
The damper controls the rate at which the piston rises under throttle opening, and the correct oil viscosity is important for proper carburettor response, too light and the piston rises too quickly, giving a momentary lean mixture; too heavy and the enrichment on acceleration is excessive. The damper level should be checked and topped up at every service.
Rebuild Lubricants & Sealants
During an engine rebuild, several specialist lubricants are essential. Cam lube must be applied to the cam lobes and followers during assembly to guard against scoring and premature wear during the critical initial start-up period, before the oil system has fully pressurised and reached all bearing surfaces. Assembly lubricant should also be used on bearing shells, piston rings, and other moving surfaces during build-up. Jointing compounds and sealants are used throughout the engine to supplement or replace gaskets on certain mating surfaces.
Wellseal is a non-hardening, non-flammable engine building sealant traditionally used by most British motor manufacturers and remains the recommended product for timing cover and water gallery joints on the B-series engine. Blue Hylomar provides a non-setting seal resistant to oils and coolants, suited to surfaces where future disassembly is anticipated. Hermetite products, including the red semi-hardening compound, the green hard-setting type, and the orange RTV silicone instant gasket, cover the remaining sealing requirements. Bearing fitting adhesive and nut-lock adhesive are also available for retaining bearings and securing critical fasteners.
Engine paint is available for owners restoring their engine bay to original appearance. MGB engines were painted dark red or maroon from 1962 to 1971, and black from the introduction of the 18V series in 1971 onwards. High temperature exhaust paint in silver, black, white, and red is available separately for refinishing manifolds and exhaust components. The MGOC Spares range covers classic-specification engine oils, SU damper oil, assembly lubricants, cam lube, jointing compounds, sealants, adhesives, and engine paint to support both routine servicing and full engine rebuilds.