1963 Chevrolet NASCAR Canted Valve Engine Exposed

No, it's not the famous 1965-Present "Rat" Big Block Chevrolet Motor. It's really an old "W" Series 409 with new heads and intake. This is the display engine located at the GM Heritage Center.

By Society Staff
reprint with permission only

The "Mystery Motor" or "Porcupine", as it was called back then, was NOT an early production Mark IV 396-427 called the "Rat" by many. It was a 1963 Chevrolet 409-427 with special heads designed for "high speed" (rpm) operation on the NASCAR speedways such as Daytona. Of course, the lessons learned with the Mystery Motor convinced Chevrolet, that it could be revamped and delivered as Chevrolet's new big block.

But first, we need to understand that GM's 1963 racing ban hammered Chevrolet's plans for competition in NASCAR and NHRA - not to mention SCCA, FIAA and USAC. The Mystery Motor had one shot to prove itself, and then it was withdrawn into oblivion . . . until the Mark IV appeared in 1965 - back then seemingly from nowhere.

As early as 1961 the brass knew that the 409 cylinder head design was at a dead end, and that a typical "wedge" engine had its limitations, but that Chrysler's Hemis needed complex valve train and the heads were heavy and huge. precluding fitment in the Corvette. They also knew that larger cubic inch engines would be needed to keep the heavier Corvette competitive in sports car racing. Thus a new approach was needed. They went back to the drawing board and came up with a compromise cylinder head that emulated the breathing of a hemispherical cylinder head with the lighter weight and size of a typical wedge head..

In a huge inspiration, they recognized that they could cant the intake and exhaust valves toward the port like a hemi AND even twist it so that it lined up with where the port had to be - allowing for ultra high-flow numbers. The new engine did not look that different until the valve covers were removed. Even then it took a discriminating eye to see the genius in the design. The stamped steel rockers sat on an individual pedestal and did not use a single rocker shaft to hold the rockers in place.

What this also allowed was Hemi-like flow with a relatively narrow head - assuring that the motor would fit in the C2 Corvette, then due out in 1963. That the later Mark IV appeared in the Corvette first was no accident. But understand that the Mystery Motor was always considered a test bed for the cylinder heads. They were already designing the Mark IV and this 1963 NASCAR gem was just a way to prove the process could result in huge HP gains.

Mystery Motor Specs

The Mystery Motor was a special casting designed to allow the fitment of the heads, but was similar in specification to the Z11 427 designed for drag racing. It had its own designation, "Mark II".

Mark II engines carried the casting number of "0-217199". The "0" denotes a pre-production casting. Also cast in the block is 9-13-62 - the date of Sept 13, 1962 in standard short abbreviated form - which is the date the blocks were cast.

In a pre Daytona dyno test, the 427 Mystery Motor made 620 HP with a single Holley on a 180 degree high rise aluminum manifold. There were 4 different intake manifolds developed for the engine. All were 180 degree design. Smokey Yunick stated the best of the 4 designs was that with casting number 0-232166.

Click HERE to Read the Rest!

For more information and additional pictures, click HERE to read the article in the May 1963 issue of Hot Rod Magazine authored by Ray Brock.



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