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Chevy Production 90 degree - V6 Engine


In 1962 Buick produced the first V6 engine. The engine was successful but had very limited popularity and so Buick sold the rights to the engine to Kaiser Jeep, later purchased by American Motors. The fuel crunch of the 70ís prompted Buick to buy back rights to the V6 engine in 1974. Buick has used this V6 with various modifications since that time.

In 1978 Chevy introduced its first V6 engine, a 200 cid engine with a 3.50" bore and 3.48" stroke. The new engine was based on the very successful small block with identical block geometry having a deck height (centerline of crankshaft to cylinder deck measured along the centerline of the bore) of 9.025" and a height (centerline of crankshaft to top of engine along the center of the 90 deg. V) of 9.805". Cylinders are spaced on 4.40" centers on each bank and the centers of cylinders on the two banks are offset to accommodate the two connecting rods on each crank journal. Cylinder banks are at 90 deg. to each other as in the small block. The V6 - 90 deg. block is therefore a small block V8 with numbers 3 and no. 6 cylinders removed. Many of the small block components including valves, rocker arms, springs, piston assemblies etc. are therefore interchangeable with the 90 deg. - V6. In 1980 the displacement was increased to 229 cid with a 3.74" bore and 3.48" stroke; virtually identical to the 305 cid small block bore and stroke. the 229 cid engine had 1.84" dia. intake valves and 1.50" dia. exhaust valves. All 1978 to 1984 V6ís were produced in a semi even-fire version.

While the 90 deg. - V8 engine produces a natural even-fire engine with each cylinder firing at 120 deg. intervals the 90 deg. - V6 engine is an odd-fire engine. In the odd-fire mode V6 engines typically run rough with excessive vibration. The odd-fire V6 operation was improved substantially by modifying the crankshaft. Each pair of adjacent connecting rods shared a crankshaft throw with the two journals offset by 18 deg. This offset produced a firing sequence of 132 deg./108 deg. or a semi even-fire sequence throughout the firing order. It also required that connecting rod lower ends be 0.050" narrower than the small block V8 engines to provide for a thrust bearing between adjacent connecting rod journals.

In 1985 a 262 cid (4.3L) engine (4.00" bore x 3.48" stroke) was introduced with a true even fire sequence of 120 deg; the internal block dimensions are identical to the 350 cid small block. This even-fire sequence was accomplished by increasing the offset between adjacent crank journals to 30 deg. In order to give the 30 degree offset the rod journal diameter had to be increased from 2.10" to 2.25" to provide enough overlap between offset journals. Connecting rods in the 4.3L V6ís are not compatible with any other Chevy engines. The 262 cid engine had 1.94" intake valves and 1.50" exhaust valves. Fuel induction systems for the 4.3L engine included quadrajet carburetors, throttle body fuel injection (TBI) and central port fuel injection (CPI).

As market conditions have required higher horsepower's Chevy has responded by increasing displacement and in 1996 Chevy started producing the 3.8L (231 cid) engine being used previously by Buick, Pontiac and Oldsmobile. Production V6/90 deg. engines use lightweight cast iron blocks, two bolt main bearing caps, nodular cast iron crankshafts and forged connecting rods.

Below is a table of the main dimensions for all production 90 deg. - V6 Chev engines from 1978 to present :

CID

Years

Bore

Stroke

Block Material

Actual CID

Litres

Main Bearing

200

78-79

3.50

3.48

Cast Iron

200.9

3.29

2 bolt

229

80-84

3.74

3.48

Cast Iron

229.4

3.76

2 bolt

262

85-94

4.00

3.48

Cast Iron

262.4

4.30

2 bolt

231*

96+

3.80

3.40

Cast Iron

231.4

3.79

2 bolt

* First produced by Buick as a 231 CID engine from 1967 to 1995.

 





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