Lewis Hamilton, Fernando Alonso, Kimi Antonelli and Carlos Sainz will start the Belgian Grand Prix from the pitlane.
All three drivers were eliminated from Spa qualifying in the first segment on Saturday.
Hamilton had his best time deleted for a track limits offence, Antonelli struggled for confidence in a low-downforce Mercedes, and Alonso was second-slowest and only quicker than team-mate Lance Stroll in Aston Martin's worst ever qualifying result.
Sunday has started with heavy rain throughout the morning and a wet track. As the forecast was for a rain-hit race, Hamilton and Alonso were on set-ups more biased towards the wet anyway.
But Ferrari has made suspension set-up changes for Hamilton and at Mercedes, Antonelli expected to change rear wing specification to have more confidence in the car and take a pitlane start, especially if it rained.
And their poor grid positions have allowed Ferrari, Mercedes and Aston Martin to strategically change engines as well.
They have all got new V6 internal combustion engines, MGU-H, MGU-K and turbochargers, while Hamilton also has a new battery and control electronics.
This introduces new components into the pool at low cost as they were going to start at the back anyway.
Sainz, who qualified 15th, will not take new engine components but has had adjustments made to his car's mechanical and aero set-up.
