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  The folks from Flint didn’t
disappoint when it came to performance, although they were a little behind the curve as
far as timing was concerned. Their Gran Sport line of cars were on the fringe of the
muscle car movement through the middle ‘60s. In 1969, Buick began to get serious with
the release of the first Stage I engine package on the GS 400. The ‘69 Stage I
featured a healthier camshaft, a 4-bbl Quadrajet with revised calibration and bigger dual
exhaust system. This added up to 345 horsepower and 440 lb.-ft. of torque for the 400
cubic inch engine, only 5 hp more than the standard GS 400 mill. The
big news from Buick, though, was the 1970 455 Stage I. The new-for-’70 engine sported
a 4.31” bore and 3.90” stroke, but the real differences were found in the
camshaft and heads. The camshaft featured .490” lift intake and exhaust, with 316°
intake duration and a whopping 340° exhaust duration. The heads received bigger valves;
2.12” intake, 1.755” exhaust, and the ports were worked to increase flow. The
compression ratio jumped to 10.5:1, requiring premium fuel to feed the monster. And what a
monster it was -- 360 horsepower and a stump-pulling 510 lbs.-ft. of torque. Even in the
heavy GS 455 A-body (3800+ pounds), the Stage I provided enough grunt to haul the car
through the quarter-mile in the high-13 to low-14 second range straight out of the box.
When the Stage I 455 was stuffed between the fenders of the radically styled GSX,
Buick’s somewhat uptight image disappeared in a blur of bright color and a cloud of
tire smoke. |
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| With 360 horses, and 510 lb.-ft. of torque, the
‘70 Stage I 455 was Buick’s top production mill. |
Buick wins the award for coolest air cleaner, as shown on this
‘67 GS 400. |
|
 Buick Stage II cylinder
heads featured redesigned round exhaust ports. The heads alone were reportedly worth 50
hp. |
Stage I was only the
beginning, however. For more serious performance, Buick developed the appropriately named
Stage II package. The components that made up the Stage II package were available
over-the-counter only, which means no production cars were built with these items. The
heart of the system was the revised camshaft. At .455” intake and .480” exhaust,
the lift figures weren’t as high as the Stage I cam, but the duration was much longer
at 340° intake and 360° exhaust. The Stage II intake was the aluminum Edelbrock B4B,
while Buick engineers tapped the 850 cfm Holley for carb duty. The undisputed star of the
Stage II system, though, was the cylinder heads. These heads featured redesigned round
exhaust ports instead of the standard rectangular versions. The intake ports were a little
different from standard Stage I fare, but the new heads were said to be good for 50 extra
horsepower on an otherwise stock engine. Special Mickey Thompson headers that mated to the
new exhaust arrangement rounded out the Stage II package.
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