The engine has remained fairly standard over the years and any Rover V8 engine is suitable for a conversion. Many compression ratios have been used and this has been achieved by different piston design. The cylinder heads were standard until the introduction of the SDI that has been fitted with single valve springs and large inlet valves for more efficient breathing. The SDI has also been fitted with an uprated oil pump (giving higher flow rate), improved crank oil seals and electronic ignition instead of points. British Leyland used the unit in automatic and manual cars and the only difference in these engines is the rear crankshaft or spigot bush that can easily be changed.
The most daunting problem with the conversion is the choice of a suitable engine. A new Rover V8 will cost well in excess of £1,600 and a factory rebuilt unit in the region of £1,200 (beware if you opt for a new or reconditioned Austin Rover engine they will not extend the warranty to cover its use in an MGB), This is rather expensive, also if you decide on one of these units it will normally be supplied minus such items as starter motor, distributor, inlet etc. and these items are extremely expensive to buy, so most people opt for a complete used unit. The most cost effective way of doing the conversion is to purchase a complete donor vehicle as they can be found at very reasonable prices. The most suitable being a SD l 5 speed manual, an added advantage of a donor vehicle is that in most cases you can ascertain the condition of the power plant and also many of the other components will be useful.
When you first see a complete Rover engine out of a vehicle, it is obvious that it is quite a monster, Removal of the power steering pump and associated hardware and the air conditioning, if fitted will reduce the problem but it is still too wide, long and tall for a small sports car like the B. When MG produced their original V8 the Rover P5B and early P6 was around, the water pup, crank pulley and alternator bracket were utilised but the inlet and exhaust manifolds, oil pump base and mountings had to be redesigned. Later type P6 Rover saloons and SD1’s are fitted with a viscous cooling fan, longer crankshaft pulley and a different design of alternator and mounting. The earlier components will have to be fitted to this unit to shorten it. The SD1 crank pulley can be machined to do the job of the earlier unit. All Rover V8 engines have an external oil pump mounted on the front cover, the base of which carries the oil pressure relief valve and oil filter. Unfortunately there is no room for this in the MGB because of the proximity of the steering rack.
A special oil pump base is available that is bolted onto the oil pump after removing the original base. This unit contains the oil pressure relief valve and oil galleries, a connection for the oil pressure gauge and two l/2" BSP outlets to enable a remote filter to be used which is usually mounted on the R/H front inner wing, a small mounting bracket is available to mount this unit as per the GT V8. As the remote oil pipes exit the pump base, they are very close to the lip of the chassis and it is best to tap this over to increase clearance. If required the oil cooler can be plumbed into the system. On the original chrome bumper V8 the cooler was mounted on the rad ducting panel under the offside fan motor and because of limited space a 10 row unit was used. With the advent of the rubber bumper V8 it was mounted underneath the same panel. Engine mounting brackets, for either chrome or rubber models are available for the sides of the engine block so that MGB GT V8 rubber mountings can be used. These engage in the existing mounts on the black bumper chassis rails and the modified units on the chrome bumper models.
The engine mounting brackets have been manufactured to mount the engine as low as possible, bearing in mind the problems with the steering etc. However if required, as with the production V8, packing pieces are available that fit between the bracket and the mounting rubber. If these packing pieces are needed they can be fitted to the steering side only in order to raise the engine and position it away from the steering. The engine oil filler and the flame trap at the front of the engine are very tall but fortunately the rocker covers can be interchanged.
Although not fitted to the works V8, a tie bar can be fabricated to eliminate the load on the engine mounts and assist with the problem of the limited clearance between the offside exhaust manifold and the steering shaft. This is mounted on the front of the nearside cylinder head and the nearside inner wing just below where the wing joins. If you decide that the engine needs a little love before the conversion do not be put of by its size. It is a fairly straight forward unit to rebuild and after market components are a lot cheaper than Rover. The engine block and also the heads on these units are quite often in very good condition even after high mileage people are surprised how little work is required. The oil pressure on the V8 is very low, the oil light warning switch on saloons operates at less than 10psi. With regular oil changes no problems occur but if not sludge builds up with resultant wear in the valve chain and these may need attention.
This site is maintained on behalf of the Cambridge & District MGOC
by Kelvin Fagan mg.maestro@mgcars.org.uk
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