This is timely as I recently completed a non-stock rebuild of a 90 degree V6 Maserati engine as was placed in the SM and Merak. Mine is a late Merak SS variant I stroked by offset grinding the crankshaft, custom (lighter) rods, altering the piston pin location and compression with more custom pistons resulting in a displacement of 3.3L. Lots of weight removed from all rotating components yet still they are rough at lower rpm, but are fabulous in peak operating ranges. With the cams and compression this engine prefers to live at 4000-8000. No vibration once it’s revved out. It hates idling, this is the nature of these. My only gripe is, compared to say a twin plug 2.8L 911 engine, the 90 degree v6, until it’s revved high, does not rev as quickly nor with that same urgency as the 911 engine twin plug race motor does pretty much everywhere. Likely due to the Maserati crankshaft weighing a good bit more? It weighed some 40lbs even after lightening while the 911 crank was about 31lbs.
Note Maserati’s new MC20 engine is 90 degree and 3 pin odd fire crank as well I believe. There have been several successful variants of the 90 degree v6 on racing in the past as well.
This same Maserati 3L engine was run at Lemans in 73-75 by the Ligier team, who won its class and placed 8th overall in 74. A 4v variant was made as well which, in final iteration, made some 420bhp at 10,500rpm. The 2v variants in race trim made about 100bhp less and obviously did not rev as high. The most well-known 90 degree racing v6 might be the Cosworth 6r4 engine which has identical bore and stroke and crankshaft pin and main journal sizes as the Maserati engine and crank. In group B, the Cosworth dominated and earned its legendary status.
More on the origins of the Maser engine for those who might be interested. The Maserati engine is also a 3 pin throw with odd fire like the Buick. Buick indeed made later modifications such as splitting the pins and adding a counter balance shaft at the center just above the crankshaft. The later Buick engines with counter shaft and split pins are indestructible.
Maserati actually built their v6 in this configuration entirely on purpose. Some have conjectured it was due to Maserati needing to cut costs this just knocking 2 cylinders off their v8. Nothing can be further from the truth as the block casting and central Jack shaft design driving the camshafts via inboard timing chains was every bit as involved and expensive to develop as would a 60 degree v6 have been. Maserati needed the low profile yet short engine design a 90 degree benefits from to fit the SM hoodline, which a 60 degree would not have accomplished.