The Exhaust
Due to the restricted space in the MGB engine bay none of the production cast manifolds used on the Rovers will fit, MG used a special cast manifold that did have a tendency to corrode and crack and at the present time this is not available, so tubular mild or stainless steel exhaust manifolds are used. This is manufactured to be as tight as possible to the block and the down pipes are routed centrally down. the sides of the block, The water drain tap on the right hand side of the block will line to be blanked
off to clear. On the nearside of the block, where the dipstick tube enters, it may need relieving to clear the manifold.
The right hand down pipe is routed between the rear of the sump and the front of the gearbox to mate up with the left hand down pipe and then a standard MGB GT V8, or competition large bore exhaust will complete the system. The standard exhaust mountings can be used with the exception of the very last mounting, which will require larger saddle clamps to accommodate the larger pipe except on the large bore system that has fittings welded to it.
If Koni rear shock absorbers have been fitted, clearance problems may have to be overcome.
Because of the redesigned front suspension on the MGR V8 the manifolds exit straight out through the lower wings through quite a large opening that does result in a great deal of road spray entering the engine bay.
Many people have asked if a twin system could be used, to give the famous V8 burble. This is possible but as there is no space between the offside rear spring and the tank, the latter would have to be modified.
The Axle
The 1800 B has used two types of axle. The early cars used a banjo axle, up to GHD3 and GHN3 132923. Later vehicles were fitted with a Salisbury or tube type, The production V8s and Cs were also fitted with the Salisbury type. Many owners run their converted vehicles on the standard axle but the Rover V8 engine in standard form is not high revving and produces its maximum torque at 2750 r.p.m. Consequently a high final drive ratio will improve the top speed, consumption and general drivability. The standard 1800 B tube axle has a ratio of 3.9:1 and the V8 has a ratio of 3.07:1. Unfortunately no suitable ratios have been made for the banjo axle.
The tube axles fitted to the 1800 and V8 are basically the same except for the crown wheel and pinion, differential cage, pinion oil seal and prop shaft flange. One point of interest is that the tube axle for the wire wheel and bolt-on wheel cars are different as the half shafts and axle tubes are of different lengths. The MGC used the tube axle in both wire wheel and bolt on (5 stud fixing) forms. These used two ratios, 3.3; 1 and 3.07, although very similar these ales were fitted with Girling rear brakes instead of Lockheed.
Although V8 crown wheels and pinions are no longer available from Leyland, reproduction items are. The 1800 differential cage can be machined to accept the V8 crown wheel. The setting up of the crown wheel and pinion is rather complex and requires some specialised tools (refer to the MGB workshop manual). A limited slip differential cage can also be obtained for the MGB axle.
The MGRV8 uses a different axle with a 3.31 ratio and limited slip however at approximately £2,000 this is not a very attractive option.
Axles from different cars, i.e. Rover SD1, 3 litre Capri, Jaguar Mark 11, have been used but obviously extensive modifications have to be carried out.
V8 Conversion Project
Overview of Project
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