Some facts about the 71 Group 2 cars.
I was one of Martin Thomas's mechanics that season and here are a couple things i remember, Martin Birrane's Boss Mustang at Thruxton s Easter meeting, Martin told his mechanics that the oil pressure was dropping when taking Church, possibly due to oil surge and oil moving away from the pick up.
So his mechanics taped over the guage so he did not worry about it.
Sure enough the engine blew during the race.
Martin was convinced his brakes were not working , so we got the man from Girling to check the system and he reported it working correctly.
Martin still convinced they did not work raced and use the gears to slow the car down for the Chicanes.
The car was brought back on a breakdown Martin claiming the clutch had gone.
On stripping the car we found the clutch perfectly ok, but using the gears to slow down had striped all the teeth off of the main gear cluster. If you know the size of the Holman Moody gears this takes some force to strip them down to nothing.
Pete