The venerable Buick 3.8 V6 has had a long and fairly illustrious career, powering many Buicks, and other GM vehicles over the past 30 years. The original design for the V6 started in the early 60s when Buick created a V6 based on the all aluminum 215 V8. The very first "Fireball" V6 displaced a whopping 198 cubic inches and shared tooling with the 215 V8. In 1963, the bore was increased to be the same as the 340 V8, which made displacement 225 cubic inches, where it stayed until 1967. Since the V6 had the same bore as the 340 V8 it could be produced on the same assembly line. This made it cheap and easy to produce for the "compact" cars in GM's car lines. The demand for the V6 was never very great and the design resulted in an uneven firing order that produced a rough idling engine, so the design was sold to Jeep in 1967.
In the 70s, with the advent of the gas crisis and the demand for a versatile, lightweight, and inexpensive engine, Buick bought the design back from Jeep in 1974. The little V6 was reworked so that it could be made on the same assembly line as the Buick 350, which entailed making the bore 3.800". Using this bore size, it could share pistons and other parts with the V6. This engine retained the original designs "odd-fire" design. (1) With each two rods sharing a common crankpin on a V8, and firing 90* apart (360* / 4 crankpins = 90*), taking one crankpin out causes a firing event every 90-90-180-90-90-180, etc. It was a balancing nightmare. This is why an odd-fire V6 is usually very unstable (read: rough) at idle.
Starting mid-way through the 1977 model year, the engine is an even-fire motor. They split the crankpins, creating a firing event every 60 degrees of crank rotation (360* / 6 crankpins = 60*). (2)
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