The obvious choice for an engine swap is the Rover v8. This engine is tried, trusted, proven and is very much the safe bet. It will fit, and there’s hundreds of examples on the road today to prove that. However, it’s very expensive and time consuming to gather all the right bits, especially if you want a more modern fuel injected variant. The gearbox options also mean that you need to replace the diff at even more expense. It’s a relatively common choice for good reason, but I like to be different so I considered other options
The engine I chose is an odd choice at first glance and is one that no-one in the world had ever done before. I chose the 3.0 GM 54° V6 X30XE from a UK Vauxhall Omega. It can be found in European Opel/Vauxhall Omega in rear wheel drive form or in Vectra, Cavalier and Calibra in front wheel drive form, and in the Saab 9000 as a turbo. It’s also available in USA in the Opel Sintra, Cadillac Catera, CTS, Saturn L-series and Vue. It’s a 200hp narrow angle V6 which suits our narrow engine bay. The engine is taller than most v6’s but the profile of the inlet manifold is perfect for our bonnet shape. The 5 speed manual gearbox has ratios that are bearable on a standard MGB 3.9 rear axle although taller final drive is desirable. The starter motor is in the right place, the clutch is operated by a concentric slave cylinder that can be driven by the MGB master and a rear drop sump is available (from a front wheel drive variant). The ECU will run the engine standalone with very easy wiring. It’s also similar weight to the standard 4 cylinder but puts out 208bhp.
This swap choice was not something I’d initially considered but my friend had one in his garage and he urged me to take a closer look, and the more I looked, the more like it seemed the perfect choice! It does of course have a few challenges but far fewer than any other engine I’d considered.