Here's a bit of a story for you.
In the mid-sixties, I was working at Ford and going to a downtown school to take a few classes. (The school is now absorbed into Wayne State University, Detroit's downtown University.) I had some time in the afternoon, and walked from school to Cobo Hall, where what is now the North American International Auto Show was in process of starting up.
Just as I got to the front doors, an eighteen-wheeler pulled into the semicircular drive. It was painted and graphic-ed with SHELBY all over it. It stopped, and a small crew in Shelby uniforms opened the back doors and started unloading the cars. One was a full competition Cobra. It, along with the others were hand-rolled onto the pavement. Very soon Shelby and a TV crew came out, and standing on the other side of the line of cars, in the middle of the drive, started into a 'stand-up' interview. The 'talking head' asked if one of the cars could be started, and one of the Shelby crew members opened the hood of the Cobra, and then got it, gave the throttle a couple of healthy hits and cranked it over.
When the 427 MR fired, it spit back through the Holley and set itself on fire. I was standing on the curb right in line with the engine, and since it was, at that time, the NAIAS was held in the cold of January, (or maybe February) I was wearing gloves. I took one step and put my hands over the the top of the carb and snuffed it out. It didn't even harm the gloves.
The 'stand-up' finished within two or three minutes and the crowd began to disperse. Shelby came over to me and thanked me, and then asked me if I wanted to go for a short ride. Cobo Hall is right on the Detroit River Waterfront and there's a drive alongside it that goes down and to the back where there's underground parking. There's also several freight elevators that were used to lift the cars onto the display floor.
We made that 2-3 minute trip into the garage and then up into the Hall. Shelby gave me a souvenir Cobra pin and he autographed a copy of the just-out book 'The Cobra Story' and gave that to me as well.
His well-known antics make it clear that he was more than a bit of an A**hole in many ways, but he treated me very well on that cold afternoon.
KS
Answer for below---The trip was very short and I don't think Shelby got all the way through the gears before we were in the garage. Acceleration was just what you'd expect from a 427 Competition Cobra.