We just purchased a 1979 450 SL in January (~60,000 miles)while it was cool and it ran fine. As summer is approaching with increasing temperatures, problems are becoming evident. In the midst of it all we had a radiator blow-out. We added stop leak to secure the leak until we could get it in for repair. The stop leak also plugged the radiator a bit and it was running about 105C in air temperatures of about 100F (but OK when cool in the morning). Under these conditions, the car started missing as if it was starving for fuel - it gradually got worse until it quit all together. After cooling off for about 2 hours it started up OK, ran for about 8 blocks and quit again. The next morning while it was cool, it ran fine to take it down to get the radiator fixed. Replaced the 2 core radiator with a 3 core, flushed the stop-leak from the system, put in a new thermostat, hoses, coolant etc, and it ran fine in the evening to go home. Next day in early morning, about 80F it ran fine for a 100 mile trip, at about 90-100C. Later in the day as air temperature rose to about 100F, car still ran at about 100C, but again started apparently starving for fuel (or ignition?) and quit again. Has anyone experienced these symptoms in similar conditions, and are there any good solutions available to prevent repeat performance in hot weather? Are there any high temperature (engine and/or air temp) malfunctions possible in the fuel and ignition systems? Defective fuel pump or ignition components at high temp? Appreciate any help - it never quits at a shop where it could be evaluated to try to pinpoint the problem. Thanks, Don R.