perfectly cancel out the primary forces and reduce the secondary vibrations to acceptable levels. The engine mounts can be designed to absorb these remaining vibrations. A 60 degree V-angle results in a narrower engine overall than V6 engines with larger V-angles. This angle often results in the overall engine size being a cube shape, making the engine easier to fit either longitudinally or transversely in the engine compartment. 90 degrees Many manufacturers, particularly American ones, built V6 engines with a V-angle of 90 degrees based on their existing 90-degree V8 engines. Such configurations were easy to design by removing two cylinders and replacing the V8 engine's four-throw crankshaft with a three-throw crankshaft. This reduced design costs, allowed the new V6 to share components with the V8 engine, and sometimes allowed manufacturers to build the V6 and V8 engines on the same production line. The downsides of a 90 degree design are a wider engine which is more vibration-prone than a 60 degree V6. The initial 90 degree V6 engines (such as the Buick Fireball V6 engine) had three shared crankpins arranged at 120 degrees from each other, due to their origins from the V8 engines. This resulted in an uneven firing order, with half of the cylinders using a firing interval of 90 degrees and other half using an interval of 150 degrees. The uneven firing intervals resulted in rough-running engines with "unpleasant" vibrations at low engine speeds. Several modern 90 degree V6 engines reduce the vibrations using split crankpins offset by 30 degrees between piston pairs, which creates an even firing interval of 120 degrees for all cylinders. For example, the 1977 Buick 231 "even-fire" V6 engine was an upgraded version of the Buick Fireball engine with a split-pin crankshaft to reduce vibration by achieving an even firing order. Such a 'split' crankpin is weaker than a straight one, but modern metallurgical techniques can produce a crankshaft that is adequately strong. A balance shaft and/or crankshaft counterweights can be used to reduce vibrations in 90 degree V6 engines. 120 degrees At first glance, 120 degrees might seem to be the optimal V-angle for a V6 engine, since pairs of pistons in alternate banks can share crank pins in a three-throw crankshaft and the combustion forces are balanced by the firing interval being equal to the angle between the cylinder banks. A 120 degree configuration, unlike the 60 degree or