A project to lift a three-storey replica engine from Brunel's SS Great Britain is due to take place.
Cranes will lift the separate display parts through the skylight on the ship's top deck before they are taken to a specialist engine maker.
The project aims to recreate a full-scale working model of the 1,300 horse-powered engine dating from 1845.
The replica engine is due to be installed and switched on in spring next year.
The engine project follows completion of work in July 2005 to the Dockyard Museum, the SS Great Britain's living quarters, and long-term conservation through the dehumidification chamber and glass sea.
Matthew Tanner, Director of the SS Great Britain Trust, said: "The reconstruction of Brunel's great engine has been a fundamental part of the recreation of the SS Great Britain."
Work is due to take place through the night on Saturday, Sunday and Monday.
When the ship returned to Bristol in 1970, she was an iron hulk. Now she sits in a Grade II-listed dry dock next to a new museum charting her history.
At her launch in 1843 the vessel was the world's first iron-hulled, steam-powered ocean-going ship.