Mopar Heritage

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To The Max

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THE BIGGEST ENGINE THAT COULD

“Max Wedge” is the name that put Dodge and Plymouth on the performance map in 1962 and forever.

It’s the name Mopar® enthusiasts gave Chrysler’s Maximum Performance engine packages for the company’s 1962–1964 factory-built drag racing cars. These machines were the catalysts that made “Mopar” the name for Chrysler performance. Dodge and Plymouth versions of the engines were introduced at the Chicago Auto Show in February 1962.

They were part of a “maximum performance” package for any model in the two car lines except station wagons. The packages were identical, except for their names. Dodge called its version the “Ram-Charger,” while Plymouth used the name “Super Stock.”

Tom Hoover Chrysler Engineering

Chrysler Engineering racing coordinator Tom Hoover caresses the new 1962 Max Wedge engine. He orchestrated the product planning and engineering sides of the project.

Tom Hoover, of Ramchargers and (later) HEMI® engine fame, led the development of the packages, endowing them with brand new “short ram” intake manifolds with staggered 4-barrel carburetors, forged pistons, heavy-duty crankshaft, a new cylinder head with larger valves and dual valve springs, a special camshaft, and “streamlined” cast-iron exhaust headers. A new adjustable cast-iron rocker arm design was used in place of the non-adjustable stamped steel rockers on all other big-block 413s. Tubular pushrods were used in place of the standard solid steel version. The list is long because virtually every part was modified on these engines—even the tri-metal engine bearings, with slightly wider clearances.

Two versions of the new Max Wedge 413 were available—one with an 11 to 1 compression ratio developing 410 hp, and another with a 13.5:1 ratio rated at 420 hp.

The complete maximum performance vehicle package included either a heavy-duty version of the T-85 3-speed manual or the A-727 automatic transmission. Also included was a 3-inch diameter exhaust system leading to “lakes” pipes that could be opened for racing. When the pipes were capped the exhaust exited through two large Chrysler mufflers to dual 2-inch exhaust pipes.

Tom Hoover Chrysler Engineering

These cast-iron headers were used in 1962 and 1963.

The 1962 Max Wedge packages were available starting at the beginning of May that year. According to exhaustive research by ex-Chrysler executive Darrell Davis, 298 Plymouths and 214 Dodges were produced in 1962 with the Max Wedge package. Chrysler’s intent was to get as many of the 13.5:1 packages as possible into the hands of real drag racers “to win at supervised drag events and bring … the recognition [to Dodge and Plymouth] of being the hottest of the new cars on the strips,” according to dealer bulletins of that time.*

The strategy worked, as the 1962 Max Wedges blew away the Chevy 409s and Ford 406s during the months following the Max Wedge introduction, moving Dodge and Plymouth from “also-rans” to the leaders of the pack on the drag strip. Tom Grove, a top Chevy 409 racer in California, said he was lured to the Mopar fold by Melrose Chrysler-Plymouth owner Charlie DiBari.

Grove immediately went out and broke all his Chevy strip records in an out-of-the-box Plymouth 413.† He also went 165.44 mph at the Bonneville Salt Flats. Grove’s Plymouths competed under the name Melrose Missile through the race HEMI era. Other racers took their cars to track records all over America, winning hundreds of trophies in the process. The transformation of Dodge and Plymouth brand’s reputations in the market was total, making them the cars to beat on the drag strip.

Chrysler upgraded the Max Wedge to 426 cid in 1963 by opening up the bore to 4.25 inches. Two versions were again available, based on compression ratio—11 to 1 and 13.5 to 1. The engines were rated at 415 hp and 425 hp, respectively. The 413 engine’s carburetors and cylinder heads were carried over. Late in 1963, the 426 was upgraded with new carburetors having .25 inch larger (1-11/16") primary throats (same as the secondaries). Other changes included a hotter cam with higher lift (.520") and more exhaust valve opening duration. Also a relief was machined in the head near the intake valve for more airflow. The engine was re-titled 426-II to signify the changes. Chrysler did not change horsepower ratings.‡

A “light-weight” package was also released in 1963 to make the Max Wedges even more dominant. Available only on the 13.5:1 package, it included aluminum right and left front fenders, hood with air scoop, light-weight front bumper and supports, aluminum front bumper dust shields and black front and rear floor carpets without jute backing. Also, the battery was moved to the right side of the trunk. In the trunk were “special carburetor air horn, hood sealing gasket and flame arrestor” for customer or dealer installations.

Max Wedge 426-III

The 1964 Max Wedge 426-III engine with its wild cast-iron “Tri-Y” Headers.

1963 light-weight package

(Top) A 1963 Dodge 330 with the “light-weight” package at the Dodge Main assembly plant in Hamtramck, Mich.

(Bottom) The 1963 “light-weight” option included these pieces. The 1964 version added a few extra pieces around the radiator and hood latch support.

The next and final Max Wedge changes were put in place for the 1964 model year when the 426-III engine was launched. It was pictured in photos with a complicated cast-iron exhaust system in which equal 21-inch branches came together in a series of “Y-shapes” that gathered each bank of four pipes into two and then into one via a steel tube manifold attached to the cast-iron piece.

These “Tri-Y” manifolds were created mainly for NASCAR because steel tube headers weren’t legal at that time, unlike NHRA and AHRA for drag racing. Cylinder heads were also strengthened and improved. Other changes included stronger connecting rods, a new crankshaft and a larger capacity oil pan.

The big news for the 426-III package was a new Chrysler heavy-duty, 4-speed transmission. A Hurst gearshift was optional for this gearbox. The light-weight package was carried over with the addition of an aluminum radiator air shield, stone deflector and hood lock supports. Every pound was counted as Chrysler left no stone unturned in the search for weight reduction.

The 426-III packages lasted only part-way through the 1964 model year—until the introduction of the 426 "Hemispherical Head" engine in the first months of the calendar year. However, these packages are still on the drag strips today, winning sportsman-class races year after year in tribute to the superiority of Chrysler engineering.

Parts for these desirable engines are still available from Mopar today. For example, two cylinder heads for the 1962–64 Max Wedge are available in the Mopar Performance catalogue: part no. P5007494 with 2.08" intake, 1.88" exhaust (the original dimensions); and P5249824 with 2.14" intake, 1.81" exhaust (the exhaust valve was made smaller to make room for the bigger intake).


*The above information is the Darrel Davis Super Stock Package guides covering the Max Wedge and HEMI® engine package cars. For copies, contact Davis at ddavis8839@aol.com. They are also available at the Walter P. Chrysler Museum, http://www.wpchryslermuseum.org.

†Grove's comments are in a multi-page Plymouth advertising insert in a 1963 Super Stock Magazine. See http://maxwedge.com/extras/63ssply.php. See also http://maxwedge.com/, an excellent source of information on the Max Wedge series.

‡Willem L. Weertman, Chrysler Engines 1922-1998" SAE International 2007. Weertman retired from Chrysler as Chief Engineer, Engine Design. He led the design of the 426 HEMI engine, among others.

See also: Hot Rod Magazine, May 1962, page 26 for a very detailed description of the new 413 Max Wedge (though they called it the "H-D" 413).

Courtesy of Mopar Magazine