Re: MX5 into MGB GT engine swap
Posted: Thu Oct 08, 2026 4:12 pm
Although the MGB engine bay is sufficiently capacious for even quite large V8 engines and the 4 cylinder MX5 engine fits almost as comfortably as the B series there are some challenges when it comes to the inner wing areas. These are narrower than those on most cars especially at the front.
Needing to make more space on the driver's side of the engine bay for an under-bonnet fuse & relay box from my donor car, one solution could be to relocate the coolant expansion bottle. Being a late B mine has a pressurised expansion tank which bears the main filler/ pressure cap rather than being a straight overflow vessel. One thought was to find a different shape tank that could be made to fit in the boxed section beside the radiator but im not convinced Id find something that would fit that shape.
Id be interested if anyone here had relocated their coolant expansion tank or replaced it with a different type.
Needing to make more space on the driver's side of the engine bay for an under-bonnet fuse & relay box from my donor car, one solution could be to relocate the coolant expansion bottle. Being a late B mine has a pressurised expansion tank which bears the main filler/ pressure cap rather than being a straight overflow vessel. One thought was to find a different shape tank that could be made to fit in the boxed section beside the radiator but im not convinced Id find something that would fit that shape.
Id be interested if anyone here had relocated their coolant expansion tank or replaced it with a different type.