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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 70’s 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 V6’s 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 V6’s 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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