The Chevrolet Z11 Drag Package

In 1962, Chevrolet was receiving increased pressure from the 421 cubic inch Super Duty Pontiacs in Super Stock and the lighter 413 MOPARs were rumored to be going out to 426 cubes for 1963. It was known that Ford would be issuing a 427 cubic inch version of their 406 as well. And everyone knew that both Pontiac and Ford would be offering “lightweight” versions of their full size cars for 1963. Chrysler was mum on the subject, but it didn’t take a rocket scientist to recognize that they would add aluminum or fiberglass parts when the season started..

As such, Chevrolet decided to respond with a complete Regular Production Option (“RPO”) package for the new year. Thus, a special 427 cubic inch version of the W-Series 409 engine was developed. It would use a stroked version of the venerable 409 and be used in the 1963 Chevrolet Impala Sport Coupe. This would be available and could be ordered under Chevrolet RPO number “Z11”.

More than just the new engine, it was part of a complete package created for drag racing only (Chevrolet had another engine in place for NASCAR – see below). The Z11 package would include aluminum engine pieces (but not the block and heads) and lightweight body parts as well as a cowl-induction air intake system, along with the new 427 CID engine.

The aluminum body parts were fabricated in Flint, MI at the facility now known as GM Flint Metal Center. Fifty of the RPO Z11 cars were produced at this Flint plant. No other run was planned as “50” was the number needed to qualify the car for NHRA and AHRA “super Stock” class.

Unlike the later second generation 427 CID V-8 (the Mark IV “canted valve” or “Rat”) which is well known, the Z11 was based on the then current W-series 348-409 engine, with the 409’s 4.3125″ bore, but with a longer 3.95″ stroke. Except for the stroke, the Z11 was not much different from the high performance 409 used in the successful 1962 S/S cars.

What was new was a high-rise two-piece aluminum intake manifold and dual Carter AFB carbs which fed a 13.5:1 compression ratio engine. This combo was able to produce an under-rated 430 HP and 575 ft lbs of torque (500 HP was more like it). GM documents show that 50 Z11 engines were built at the GM Tonawanda engine plant and were mated to the 50 cars produced in Flint. 20 partial engines were put together for replacement parts and over the counter purchase. All the cars were to be delivered to established racers with a record of success with 1961 and 1962 409-engined cars.

NOTE: This engine should not be confused with the 427 NASCAR Chevrolet that Junior Johnson and others showed up with at Daytona in 1963. That engine had cylinder heads similar to what would become the 396-427 introduced in 1965, but it was a hybrid between the “W” series 409 and the later engine, sporting the same bore and stroke of the W-Series 427 block to reach 427 cubic inches. It did, however utilize a modified and recast 409 block. But it was a special casting as were the unique heads that were not the same as the later Mark IV 396-427. To learn more about “Mystery Engine” – click HERE.

The Z-11 was produced only in 1963, and it was a complete package. The RPO Z11 option was an additional $1240.00 ($11,844.67 in 2022 – no small change even today). Here are the unique specifications and part numbers:

    • Full Vehicle shipping weight – 3,245 lbs.
    • Vehicle curb weight – 3,405 lbs.
    • The 427 CID engine was rated at 430 HP @ 6000 RPM. (Actual horsepower was 480-525)
    • Block casting #3830814 – Casting Code “QM”
    • Block part number #3838253
    • Cylinder Heads #3837731  (2.19″ intake and 1.72″ exhaust)
    • Valve Covers #3837739 (left), #3837740 (right)
    • Oil pan (deep sump) #3816322
    • 2 piece aluminum intake manifold #3830623 (top) #3837733 (bottom)
    • Water pump #3837691 (aluminum)
    • Cam #3837736 (0.556″ intake and 0.556″ exhaust lift with 325 degrees duration
    • Crankshaft #3837472
    • Distributor #1111023
    • Coil #1115107
    • Generator #1100628
    • Starter #1107274
    • Special cowl induction air cleaner #6418986, with #3839764 (duct)
    • Tachometer (with redline at 6200 RPM)
    • Borg Warner T-10 4 speed transmission (close ratio)
    • Special anti spin rear with 4.11:1 rear gear ratio
    • Sintered metallic brake shoes and Screened rear brake backing plates with air scoops
    • 15″ X 5.5″ wheels with 6.70 X 15 bias ply tires
    • Front coil springs #3824693 and deleted front sway bar
    • Rear coil springs #3824694
    • Optional sound proofing and insulation delete (on most delivered cars)
    • Optional heater delete (on most delivered cars)
    • Hood #3837710 (aluminum)
    • Hood catch #3837718 (aluminum)
    • Grill filler panel #3837750 (aluminum)
    • Left fender #3837765 (aluminum)
    • Right fender #3837766 (aluminum)
    • Front bumper center #3837751 (aluminum)
    • Front bumper LH #3837755 (aluminum)
    • Front bumper RH #3837756 (aluminum)
    • Rear bumper center #3837752 (aluminum)
    • Rear bumper LH #3837753 (aluminum)
    • Rear bumper RH #3837754 (aluminum)
    • Front bumper bracket LH #3837763 (aluminum)
    • Front bumper bracket RH #3837764 (aluminum)
    • Rear bumper bracket LH #3837757 (aluminum)
    • Rear bumper bracket RH #3837758 (aluminum)
    • Rear frame to bumper brace LH #3837759 (aluminum)
    • Rear frame to bumper brace RH #3837760 (aluminum)

The Z11’s race history was abortive as the cars found themselves factored into A/FX (Factory Experimental) or A/LP (Limited Production) rather than S/S, due mostly to Chevrolet’s abandoning all official racing programs starting in 1963 and the 50 cars were not fully delivered in time. Most became match race drag cars where they fared much better in the hands of people like Bill Jenkins and Dave Strickler.


427 CID The Z11 did not look much different from the 409 CID until you looked closely. The intake was a two-piece high rise unit, being the most obvious.

Pioneered in NASCAR, the cowl induction intake was designed for ram air induction at speed. Except for supplying cooler air, the unit was only effective at over 100 MPH.

427 CID The Z11 in cutaway. Drawing by David Kimble, and courtesy of Chevrolet division.

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