Saturday July 16
The weather today was perfect, with the sun hidden behind the clouds most of the day. Warm, but not hot. We had an early morning practice and began to notice a bit of a misfire at high RPMs in 4th and 5th gear. The crazy thing was that if we let the pedal just off the floor, the issue went away. Using the old air-fuel-spark adage, we figured that the mixture was off. We recently changed from Stromberg to Weber carburetors and hadn’t adjusted the fuel pressure, so this seemed likely. The thought was that there wasn’t enough fuel at the high RPMs. So before the qualifying race we moved the pressure from 2.5 to 3 PSI.
Unfortunately, our theory turned out to be incorrect. About 4-5 laps into the qualifying race the miss returned. We ended the session a little slower and qualified 19th for the race on Sunday, just behind a pair of Datsuns and a myriad 911s.
After the race, we returned to the paddock and asked around to see if anyone had had a similar issue. A good friend driving a beautiful Lotus Europa recalled having the exact same problem a few years before. He said it wasn’t air or fuel, rather spark. As the race goes on, he said, the battery (unaided without an alternator) loses power and just can’t fully ignite the fuel-heavy mixture. It seemed to make sense, since letting up on the throttle leans out mixture and helps it burn easier, and matches our symptoms.
With that in our minds, we packed as many electrons into the battery as we could before heading home for the night, hopeful of a successful race.