There have been a few V8s with an angle of 70 to 75 degrees between the cylinder banks, some of them quite successful. Perhaps the best known would be the Ford (Cosworth) HB and Zetec-R Formula 1 engines, around 20 years ago.
But to my knowledge, the only one with a 45-degree angle was Harry Miller’s 308ci V8 for his four-wheel-drive Indy cars, two of which were built in 1932. Unlike their L8 and L4 predecessors, these engines seem to have had no success. In fact, it was replaced in 1934, in one of the cars, by the contemporary Miller 255ci L4, which then performed much better, on at least one occasion leading the Indy 500 for a long while.
Is it possible that the failure of this engine is at least partly attributable to the unusual angle mentioned above? Certainly, with a conventional flat-plane crankshaft (assuming that is what was fitted) the firing strokes would have been very unevenly spaced: alternately 45 and 135 degrees apart, instead of the even 90 degrees apart of the V8 with the usual 90-degree angle between the banks of cylinders. Could this have adversely affected reliability, to the extent that the engine had an appetite for main bearings, as one writer has it?
To some extent, this idea has originated with an analysis I read, of the torsional vibration failures suffered by the Liberty V12 aero engine of the WW1 era. That analysis concluded that the unusual 45-degree angle between the cylinder banks, as opposed to the usual 60-degrees, was the root cause of the vibrations. And it is certain that a 45-degree V8 cannot be as well balanced as the usual 90-degree arrangement, being subject to both vertical and horizontal vibration, apart from any torsional disturbances that might also be present.