When a Rolls Royce cuts off, look for a Buick mechanic.
I have a 1955 Rolls Royce which was modified with a 1972 Buick engine and transmission several years ago. I drive it only occasionally. Recently, it developed a problem of seeming to "cut off" the electrical power to the engine for a moment every three or four minutes while driving. Both the lights and engine completely lose power. If driven several miles, the battery is discharged. Your diagnosis?
TOM: Whatsa matter Floyd, the Rolls Royce dealer won't let you anywhere near his shop? Does he come out chasing you with his umbrella when you try to drive into the parking lot?
RAY: Luckily, it shouldn't take a Rolls Royce mechanic to fix this, Floyd. Start by checking all of the obvious stuff--the connections to the battery and starter, the output of the alternator, and the fusible links. While the car is running, you should also jiggle all of the wires that run from the positive terminal of the battery. That will tell you if the problem is a bad wire. If you don't find your problem there, my guess is that you're missing a crucial ground connection from the frame of the car to the engine block.
TOM: The good news is that you don't have to find a bad ground to repair it. You can simply "break new ground," as they say, by running a new wire from anywhere on the block to anywhere on the frame. Just to be on the safe side, I'd also replace the ground that runs from the frame to the negative terminal of battery.
RAY: And just for added insurance with this strange hybrid, Floyd, I'd try to find a Buick mechanic named Nigel or Trevor.