what is the number of drivers who didn't finish the race due to engine trouble?
6
Pos No Driver Constructor Laps Time/Retired Grid Points
1 5 Jim Clark Lotus-Ford 80 1:59:25.6 1 9
2 2 Denny Hulme Brabham-Repco 80 + 12.8 4 6
3 8 Chris Amon Ferrari 80 + 16.6 6 4
4 1 Jack Brabham Brabham-Repco 80 + 21.8 3 3
5 12 Pedro Rodriguez Cooper-Maserati 79 + 1 Lap 9 2
6 7 John Surtees Honda 78 + 2 Laps 7 1
7 15 Chris Irwin BRM 77 + 3 Laps 13
8 20 David Hobbs BRM 77 + 3 Laps 14
9 14 Alan Rees Cooper-Maserati 76 + 4 Laps 15
10 18 Guy Ligier Brabham-Repco 76 + 4 Laps 21
Ret 19 Bob Anderson Brabham-Climax 67 Engine 17
Ret 6 Graham Hill Lotus-Ford 64 Engine 2
Ret 4 Mike Spence BRM 44 Ignition 11
Ret 9 Dan Gurney Eagle-Weslake 34 Clutch 5
Ret 22 Silvio Moser Cooper-ATS 29 Oil Pressure 20
Ret 11 Jochen Rindt Cooper-Maserati 26 Engine 8
Ret 3 Jackie Stewart BRM 20 Transmission 12
Ret 10 Bruce McLaren Eagle-Weslake 14 Engine 10
Ret 17 Jo Siffert Cooper-Maserati 10 Engine 18
Ret 23 Jo Bonnier Cooper-Maserati 0 Engine 9
DNS 16 Piers Courage BRM 0 Non Starter
csv/204-csv/641.tsv