GM debuted a newer RWD H-body hatchback platform for 1975
models, an adaptation of the older Vega body style but,
slightly longer. Chevrolet's entry was this HR07 Chevrolet
Monza 2+2 sport coupe. Originally designed for a Wankel
motor that was never produced, Chevrolet offered two engines
for 1975 models.
POWER TEAMS (1975)
Engine
HP
4-
Speed
Turbo
Hydra-
matic
2.3L
2-bbl Four
87*
Std. (1)
Std.
Avail.
4.3L (262 cid)
2-bbl V-8
110
Avail. (1)
Std.
Avail.
(1) California Emission
Equipment required in California
*80 HP with California Emission
Equipment
Dealer promotional commercial for
Monza Mirage
The 1975
Chevrolet 1HR07 Monza 2+2 Hatchback debut
GM's first car project designed using CAD technology was the
H platform
Chevrolet Monza. They needed an answer to the
1973 gas crisis and other entries of foreign subcompacts and
Ford's 1974 Mustang II,.
The car was originally designed to be powered by GM's new
Wankel engine that was under development but later dropped
because of reliability and fuel economy issues. Also,
expensive royalty payments to the patent holder made the
engine platform less appealing. It was essentially a Vega
H-body rear wheel drive chassis lengthened by 4 inches for styling and to
accommodate enough space for a Chevrolet small-block V8. GM
had high hopes for their new EPA driven down-sized sports
sedan with good performance potential.
Chevrolet's new 1975 Monza, hit showrooms with three
different models; a mid-year introduced notchback coupe and two hatchbacks, the S, and
the 2+2. But, sitting next to the
hatchbacks that debuted to the press in July 1974, was
Chevrolet's full-bore, flared-fender Monza racecar. It was made
possible only through the efforts of Vince Piggins, who led
Chevrolet's Product Promotion Engineering Department.
The 1977 Chevrolet Monza Mirage
Styling for the new trim package took its
queue from the highly successful IMSA Monza GT racecar.
It was so visually appealing, it gave rise to the idea of an
optional sporty street
version.
The result was the 1977 Monza Mirage.
In the beginning,
GM commissioned Michigan based BORT (British Overseas Racing
Team) of Grand Rapids, Michigan to design a special limited edition
trim package that could be easily applied over a factory
finished Monza body.
Michigan Auto Techniques Corporation (MAT),
an aftermarket company, was contracted to manufacture
and install the components for the 8,000 or more orders
originally anticipated. The body flares and spoilers
were manufactured using Reaction Injection Molded (RIM)
polyurethane material.
The Monza Mirage package from Michigan
Auto Techniques Corporation
The Monza Mirage sport package was ordered through
participating Chevrolet dealerships. A 1HR07 Monza 2+2
Hatchback Coupe in Antique White (11L-11U) was
specified, and with any available 1977 interior.
Following assembly of a Monza 2+2 hatchback at GM's
plant in St. Therese, Quebec. Then it was drop shipped
to MAT in Grand Rapids, who installed the special Mirage
body panels, decals and stripes. The RIM panels were
attached directly to the factory fenders with
pop-rivets, similar to installation of vinyl siding on a
house, after which, the decals were also applied.
Fourteen separate urethane body parts
were mechanically fastened over the factory finish of a new Monza. The front air dam was shipped inside the vehicle for
dealer installation to facilitate loading and unloading
during transit.
Some Monza Mirages were produced with the
standard 140 CID (2.3L) Overhead Cam
two-barrel L-4. The only
available V-8 engine for the '77 Monza was a 305 CID (5.0L)
2-bbl, which replaced the 262 CID (4.3L) 2-bbl V-8.
Each Monza Mirage serial number, from Michigan
Automotive Techniques Corporation (MAT), was
affixed to a self-adhering embossed vinyl
"Mirage" plaque located in the interior. Mirage
serial
numbers were consecutive and recorded
along with the VIN at MAT.
There were approximately 2,400 Monza Mirages
turned out by MAT. Additionally, some Mirage
packages were assembled at dealerships. The
entire sport package was available to the public
and could be ordered from dealer parts
departments.
End of Trail for H-body RWD
A total 731,504 Monzas were produced in six years. The
H-body rear wheel drive Monza, Sunbird, Skyhawk, and
Starfire were replaced in the spring of 1981 by GM's new J
platform line-up. The J-body (FWD) line-up for 1982 included
the 1982 Chevrolet Cavalier, Oldsmobile Firenza, Buick
Skyhawk, and Pontiac J2000.
Because the forthcoming J-body cars were to be sold as 1982
models, there was a long production run of 1980 H-body
models in order to provide sufficient inventory to carry
dealers until the spring of 1981. GM's so called H platform
designation was reintroduced in 1986, but as its new
full-size front wheel drive line up.
In 2008, there were an estimated (25-30) '77 Monza Mirages
in running order.
This
is the IMSA GT racecar that inspired the Monza Mirage
street version. The racecar was created by Lee Dykstra and
Horst Kwech of DeKon Engineering, LTD. DeKon
c/n1005 is driven by Horst
Kwech at the IMSA Camel GT, 6 Hours of Mid-Ohio endurance
race on August 24, 1975. The car sold to notable
racer and friend Allan Moffat later in the year. He fell for
the car's ease of handling and top speed of 202 mph at
Daytona.
Al Unser piloting
a Monza DeKon c/n1003 tube-frame racecar at IMSA
Camel GT - 250 mile Daytona Finale on November 30, 1975.
Al Holbert owned and drove this championship winning Monza,
chassis no. 1008 was built by DeKon
Engineering. Photo taken at the Daytona Finale 250-mile IMSA Camel GT
race Nov. 28, 1976.
The red, white
and blue DeKon cars, specifically the No. 1 car campaigned
by Mike Keyser, made an impact on the public. Think about
it, American cars racing against domineering foreign cars on
American soil during the American bicentennial year, and
then actually winning.
Mirage's Inspiration... IMSA silhouette racecars
The car was interesting enough to convince John Bishop of
the International Motor Sports Association (IMSA) to
initiate an entirely new racing class to allow "silhouette"
construction techniques, in which the profile of the car
stayed relatively the same, but covered a purpose-built,
tube-frame chassis.
Racers were anxious to get their hands on something that
would give Porsche a run for their money in the burgeoning IMSA Camel GT
Challenge Series and its new class AAGT (All-American Grand Touring).
The
General Motors Corporation contracted with DeKon
Engineering, LTD of Libertyville, IL to design and build the
first of several Monza bodied race cars. DeKon was the
partnership of automotive engineer Lee Dykstra,
formerly with Kar Kraft Engineering, and Horst Kwech
a racecar builder and SCCA Trans-Am championship driver. The
company name was a concatenation of 'De' for design and 'Kon' for
construction and used the first letter of the owners last
names.
In late
1974, DeKon received their first Monza body, a stripped
chassis, produced at GM's St. Therese assembly plant in
Canada and began building chassis #1001. The new race chassis
used structural tubing to build a space-frame that was clad
with an OEM Monza tub. Only the
original doors, roof, and rear deck lid remained. The front
end of the factory chassis was cut off and fitted with
specially designed serviceable framework for the engine and
new fiberglass body panels. The original fenders were
replaced with wide fiberglass flares. An aerodynamic front
air dam and rear wrap-around spoiler was added. A custom
designed coil-over suspension was bolted to the frame along
with large
diameter air-cooled brakes and Lockheed 8-piston calipers.
Big beefy
slicks were mounted on lightweight BBS wheels at all four corners. Extensive testing took place at GM Technical Center in Warren, MI to analyze
the racecar's suspension and handling characteristics.
A 5.7 liter Chevrolet
small-block V8 engine that developed as much as 600 hp was selected and strategically
positioned within the new frame. It was pulled back to the firewall and
offset a few inches from center to counter-balance the
driver's weight. This gave the DeKon Monza a near 50/50
weight distribution. The car weighed approximately 2,400
pounds when complete.
Chevrolet's showroom stock Monza had a MSRP of just under
$4,000. Then DeKon transformed into a lightning quick silhouette
racecar for around $37,000. They built fourteen Monza
racers, although not all of their chassis have an
identification plate. There were also many
other privateers who built Monza racecars for IMSA and
Trans-Am racing. DeKon became the most successful and well
known of the HO7 racecar builders.
Monza Motorsports
Monza's participation in the IMSA Camel GT Challenge Series
new AAGT class allowed them to compete with the best GT cars
in the world. The 1975 season was launched with the new cars
that would compete with the dominating Porsche Carreras. A
very liberal set of rules allowed some body panels to be
retained - the windshield, the rear window and the roof.
Everything else was built from scratch.
Al Holbert saw the potential of the Monza. By the end of the 1975
season, he ordered a brand new car prepared by Dekon
Engineering. Chassis #1008 would be used starting for the 1976
season. Holbert won the IMSA Camel GT
Champion in '76 and '77, beating Hans Stuck, Brian Redman,
and Peter Gregg. Al's successful 1977 campaign he captured another
IMSA crown. Unfortunately, it would be the last title for an
American car.
The Porsche 935s were becoming unbeatable
right from the beginning of the 1978 season when IMSA
allowed the German cars (two) turbochargers. But, the
Dekon Monza left its footprint on the IMSA
Camel GT series. They were quite unbeatable in 1976-1977.
Chevrolet Monzas disappeared from the IMSA circuit after
1986, and descended to the ranks
of the SCCA Trans-Am pro series and its amateur club
racing.
Today, Monzas are still
roaring around the track at vintage races on the west
coast, out east, and down south.
The cars are still very exciting for race fans
to watch. A ground-up replica of
Monza DeKon #1006 was recently built in France and
appears at the Le Mans Classic. The asking
price for a race-ready Monza is said to be more than
$250.000.
numbers were consecutive and recorded
along with the VIN at MAT. 
