Clunking when on/off power

This is something that's been bugging me since the motor was removed and rebuilt last year, maybe 15,000 km ago. I'm pretty sure it wasn't there before the engine came out but as always with such things, my memory may be fooling me.



Most of the time, you can drive the car and it's smooth and silent. Then, for no discernible reason, when you lift off or power on, you get a bang or clunk (it varies). It sounds like it's happening at the right front, and weirdly, sounds like it's high under the bonnet.



Very rarely, as you move off, immediately as the clutch bites, you'll get a bang that sounds like it's above your legs.



Is there an engine stay that could be loose or have a stuffed bush? Play in such a beast would explain the noise.



Similarly, is there a suspension bush that I should be checking?



Wheels are another option but I've just rotated the wheels and I can assure you the wheel nuts are tight, as they were before I did the rotation.



The other option would be drive train however, if this was the case, wouldn't the noise be there all the time? It genuinely is a case of quite a few kilometres (10 or more) of silent running, followed by a short spell of noisy driving.



Of course, it could just be my lousy driving but I'll be stuffed if I can drive quietly when the noise is there whereas I can't provoke it when then noise isn't there (ie, deliberately jerky driving makes no difference)



Any guidance short of a rag in the petrol tank and a match would be appreciated.

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