06-07-2022, 01:59 PM
Wind resistance makes a huge difference. On a chummy, open the top half of the screen - it's worth about 4 m.p.h. Take the screen off and it seems to add about 7 m.p.h. In the late 1960s, late at night in PL3002, I drafted a friend's mini van on a flat section of road and, with its well-run-in but standard engine, it clocked 75 m.ph. on the van's speedo - so, say 69 m.p.h.? On the same night, I ran the car for several miles flat out with the ignition well retarded. Stopped, opened the bonnet and the exhaust manifold was glowing red hot. Oh, how hard we used our 7s then.