Just purchased a 1972 250C in Leesburg, VA. When I was driving it home to Bridgewater, VA on Rt. 66, it maintained a steady engine roar. Car does not vibrate. All the noise and vibration seems to be under the hood. It sounds like a huge fan (humming) that may be off balance. Could it be transmission. The car does have new motor mounts---could this be the problem?

Does the engine vibrate? If not and it is just noise, it could be a leaky exhaust manifold (had that on my 250C). Put it in park (with handbrake on), open hood, and push throttle. See whether noise gets louder with rpm. If vibration is present, then you have a whole other problem.

Good luck,

Bert

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'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8

How fast were you going? I have the same car and it seems to be geared short, ie the engine is spinning fairly quick.

You might have a stuck cooling fan hub. Try spinning the cooling fan, engine off, by hand. It should turn freely.