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Illustrated Corvette Series No. 132 - 1970-1/2 -
1972 ZR1 Corvette
"The Original ZR1"
By 1970, the Detroit horsepower party
was largely over, and GM management was planning radical changes for
‘71 and beyond. There was a growing awareness of the health
hazards of breathing fumes from leaded gasoline, along with increased
pressure from insurance companies to curb the escalating output of
domestic cars. But while the GM brass were putting the kibosh on
performance, Zora Arkus-Duntov was doing his best to keep it alive.
In February of ’69, John
DeLorean was top dog at Chevrolet. Knowing the direction that GM
president Ed Cole had mandated, DeLorean and his Corvette product
planners were tasked with creating a new theme for the Vette: the
luxury sports car. The Custom Interior Trim option cost just $158 and
included leather seats, woodgrain trim on the console and door panels,
and special carpeting. This was just the beginning of the added
creature comforts that would define the Corvettes of the
‘70s. .
But Duntov wasn’t about to
let the hard-core performance crowd go without some goodies to race
with. The L88 was history, and the ZL1 was only available as a crate
motor. The hot new performance engines were the LT-1 350 small-block
and the LS5 454 big-block. If racing was your intention, there was the
LT-1–based ZR1 option, along with the (planned) LS7-based
ZR2. Unfortunately, the ZR2 never made it into production in
‘70, but it did make a brief appearance in ’71 with
a somewhat detuned 454 LS6. The ‘71 model year was the only
one for the $1,747 ZR2 option, with just 12 units produced. The cure
for the lower-compression LS6 was simply a set of dome-top pistons. The
ZR2 was the base car for John Greenwood’s entry into road
racing in the ‘70s.
The ZR1 and the ZR2 were officially
designated as “off road,” which translated to
”racing only.” Like the ’67 to
‘69 L88 cars, the ZR Corvettes were not happy on the street,
but they did provide an excellent base on which to build SCCA Class A
or Class B racers. The ’70 ZR1 package cost $968 and included
the following: the solid-lifter, 370-horsepower LT-1 engine; an M22
four-speed transmission; heavy-duty power brakes; a transistor
ignition; a special aluminum radiator; a metal radiator shroud; and
special springs, shocks, and front and rear stabilized bars. There was
also a long list of options that were not available. These included
power windows, a rear-window defroster, air conditioning, power
steering, deluxe wheel covers, an alarm system, an AM/FM radio or
stereo, and an automatic transmission. Racing fender flares were
included in the trunk space, and a cold-air scoop and header-type side
exhausts were sold separately. As with the L88 package, Duntov wanted
to discourage customers from buying a car that wasn’t
designed for street use. There were 25 ZR1 units built in
‘70, 8 units built in ’71, and 20 units built in
‘72. When the 454 ZR2 option was released in ’71,
only 12 units were built. All of the ZR Corvettes were built by
Chevrolet’s “Repair Department” in St.
Louis.
The ‘70-1/2 Corvette also
received a minor makeover. There was the revised, egg-crate grille that
matched the new egg-crate side vents, square front turn-signal lights,
rectangular exhaust tips, and flares on the back edges of the front and
rear wheel openings. The LT-1 and ZR1 options included the big-block
hood with special pinstriping and “LT-1” lettering.
Positraction and tinted glass were standard, and there was no charge
for transmission choice.
It would be 18 years before
the ZR1 name would resurface in ’90, and another 19 years
before the ‘09 version showed up. It was definitely worth the
wait!
Illustrated Corvette Series No.
43 - 1970-1/2 Corvette
"Lots of Hot Stuff"
Corvettes
have always had something of a split personality. Defined as a "sports
car", but with musclecar straight-line, scare-you-to-death
acceleration. Detroit learned early in the performance game that
there's no substitute for cubic inches. But the penalty is extra
weight. When the Corvette went "big-block" in '65, the split widened
between the sports car and musclecar groups. The 1970 LT-1 option gave
buyers the best of both worlds.
Although Zora Arkus Duntov loved the brutish big-blocks, his "ideal"
for the Corvette was a balanced, mid-engine, small-block layout. After
many attempts, the mid-engine Corvette just wasn't to be. His plan-B
was to make a high-revving, high-performance, lightweight small-block,
with a 50/50 weight distribution. The resulting LT-1 option just blew
everyone away.
The LT-1 engine had about every trick part a production car could have.
Designed as a high-revving performer, everything was stout. The
cast-iron block had four-bolt main caps and a forged crankshaft at the
bottom end. The connecting rods and pistons were forged and had 11:1
compression.
A dual-plane aluminum manifold and 4150 Holley four-barrel rated at 800
cfm handled the intake side. Over-sized valves in performance heads and
solid-lifters along with a high-life cam gave the LT-1 a lumpy, "don't
mess with me" idle, and cast-iron manifolds with 2.5 inch pipes. The
ignition system was the latest transistor Delco model.
It all added up to 370 ponies at 6,000 rpm, and 380 ft-lb of torque.
With the relative light weight of the small-block, the LT-1 was just a
tick off the straight-line performance of the 454. Quarter-mile-times
were around 14.10 seconds at 102 mph, with zero to 60 times around 6.5
seconds. But the best part was that because of the balanced
arrangement, the LT-1 could be driven as deep into corners as Europe's
finest. Some publications reported that the LT-1 was as fast, if not
faster, through the curves than the 1970 911 Porsche!
The LT-1 option wasn't cheap though. At $447.60, it was $10.50 more
than the '69 L71, 427/435 engine and $157.95 more than the '70 LS5,
390-horsepower 454. For 1970, Chevy sold 1,287 LT-1 Corvettes.
Interestingly, the air conditioning option was $447.65, 5 cents more
than the LT-1, but not available with the LT-1, as was an automatic
transmission.
There was an option called the ZR-1, that was a small-block "package"
version of the off-road L-88. Only 25 were ordered. For some, the 1970
LT-1 was the finest C3 Corvette made.
llustrated Corvette Series No.
44 - 1970-1/2 LT-1 Corvette
"Balance of Power"
Imagine having a new Corvette
with more power than a big-block, and the weight of a small-block. That
was the basic idea behind the all-aluminum, 427 ZL-1 Corvette. The idea
of an all-aluminum engined Corvette was first outlined in 1957 as the
"Q-Corvette." What finally emerged was more than anyone ever expected.
While
everyone loved the 427's power, Duntov was not happy to have 51% of the
Corvette's weight over the front wheels. Some calculating showed that
if the engine was completely made of aluminum, the weight would be
close to a small-block. So it was decided to go-for-broke and make the
ZL-1 a monster.
Duntov
started with a "stock" L88 and added an aluminum block that was fitted
for a dry-sump oil system, larger main bearing bulkheads, extra
cylinder head bolts, 12:1 compression pistons, a new camshaft, and
open-chamber aluminum heads. Cast-iron sleeves were installed in the
piston bores to solve the wear problem with the aluminum block. With a
set of headers, the ZL-1 made over 585 horsepower at 6,600 rpm! Since
the L88 was already void of unnecessary street hardware, the ZL-1
optioned Corvette weighed in at only 2,908 pounds, about the weight of
a 1957 Vette.
The big
hitch for the ZL-1 was its price. The ZL-1 option alone cost $3,000 on
top of the L88 option. That made the ZL-1 cost over $10,000 in 1969!
That was almost twice the cost of a normal 427 street Corvette.
Only two
ZL-1 Corvettes were ever made, making them the rarest Corvettes ever.
Performance was amazing: 12.1 quarter mile time and 180 mph top speed.
This was really Chevrolet's all-out racing Corvette!
lIlustrated Corvette Series No.
45 - 1970-1/2 454 Corvette
"Gobs of Power and Confusion"
Nothing exceeds like excess,
and the '70-454 Corvette was a perfect example. Between the car
magazines, published brochures, and what was really available, there
was almost as much confusion as there was power.
What John
Q. Public was actually able to drive home from the Chevy dealer was the
390 horsepower, LS5 454, which wasn't too shabby. The LS5 option was
reasonably priced at $289.65, and 4,473 LS5- equipped Corvettes were
sold in the half-year of 1970. The extra cubic-inches pumped up the
torque to 500 lb-ft. Even though on paper, the LS5 looked like it had
lost 45 ponies from the 427/435 '69 big-block; on the street, the
difference was nil.
Power
figures for GM cars was kind of a black magic shell game. For years GM
wouldn't sell cars with more than 400 cubic inches. That changed in '66
when the 1965's 425 horsepower L78 396, became the L72, 427 that pulled
425 horsepower. So what was the real power of the 427? The L72 almost
got a decal reading "450 horsepower," but corporate politics downplayed
the figure. The '67, '68, and '69 L71, 427/435 tri-carb engine was
rated at 435 horsepower, but was closer to 450 to 475 horsepower. All
of the Detroit power numbers were somewhat misleading because published
figures were "gross" power ratings. Engines were tested without
mufflers, accessories, or even a fan. Real cars have all sorts of
power-robbing aspects, but it all makes for great bench racing.
There
were several 454 variants that were very interesting. The
450-horsepower, LS6 454 never made it into the Corvette for '70- , but
was an option in the Chevelle. Then the LS6 showed up as an option for
the '71 Corvette, but was de-tuned to 425 horsepower. Even more exotic
was the LS7 454, rated at 465 horsepower. This option was listed in the
Corvette shop specs, but only one was "officially" made. The LS7 was a
stroked version of the L88. Supposedly, Duntov gave a wry wink, and
signed the order to have all LS7 prototypes destroyed. Sometime between
1973 and 1975, an LS7 was stolen from Chevy Engineering by a few guys
who jumped the fence.
Perhaps
the most unusual 454 prototypes were the
LT-2 and
the LJ-2. The LT-2 was a 454 version of the all-aluminum ZL-1.
Increasing the stroke on a high-revving racing engine probably wasn't a
good move. The LJ-2 was a 454 version of the solid-lifter 427/435
tri-carb L71. This beauty was rated at 460 horsepower.
By the
end of 1970, the party was over. Rising insurance rates, tougher
emissions regulations, and no-lead gas put a lid on things. In the long
run, big-block engines took the Corvette away from "sports car" to
"street bruiser." Duntov liked the power, but didn't miss the weight of
the big-block. But oh, the wonderful sound of a big-block Corvette!
lllustrated Corvette Series No.
40 - 1970 XP-882 Corvette Show Car
"Experimental Corvette - Bad Timing
It
was a great day for Corvette fans. When the crowds piled into the New
York Auto Show on April 2, 1970, they had no idea what Chevrolet was
proposing as the next Corvette. The XP-882 Mid-Engine Experimental
Corvette had almost everything a Vette lover would want... big-block
power, huge wheels and tires, exotic suspension, drop-dead looks, and
the engine located in the middle of the car, exactly where an exotic
car engine should be.
But we all know how the story ended; they didn't come close to making
the car. Forward thinking just couldn't overcome bad timing. Duntov's
design team started working out the mechanical challenges for the
XP-882 in 1968. Styling penned up a new look that screamed "Corvette!"
It was crisp, edgy, modern, yet it "looked" like a Corvette.
New Chevy General Manager John Z. DeLorean stopped work on the XP-882
to pursue making Corvettes based on the new, inexpensive Camaro
chassis. DeLorean met with fierce resistance from styling, engineering,
and sales to NOT take the car in that direction. So the project was
stopped in 1969 and was warehoused until 1970. When Ford announced a
similar mid-engine project with DeTomaso, DeLorean resurrected the
XP-882 and had it finished for the show car circuit. Because there were
no press releases, everyone was stunned. The car magazines were all
over it, initiating a feeding frenzy of speculation.
Mid-engine cars were very exotic in the '60s. Not only was the engine
midship located, but it was transverse mounted. By using the
front-wheel drive, automatic transmission from an Olds Toronado, Duntov
was able to quickly get a working prototype. Suspension and brakes were
obviously independent and disc. Wheels were spun-aluminum, with vent
slots, and tires were E60x15 on the front and G60x15 on the rear. The
interior of the car was basic prototype fashion, no frills and no real
design at that point. The XP-882 was never officially tested for speed
and performance.
Many other Corvette show cars have been more thought out than the
XP-882, but the car was rushed into service and not fully developed
like show cars of the '60s. But the timing couldn't have been worse for
an all-new Corvette. The new platform was going to be expensive to
make, requiring new transmission, suspension, body, and interior parts.
Actual production wouldn't have started until '72 or '73, just in time
for the first Arab oil embargo. Also in the brew was a GM internal push
to develop a Wankel-engined prototype, so the second XP-882 chassis was
made into the 1973 4-Rotor Aerovette.
All things considered, the XP-882 didn't have a chance, but it sure was
exciting.
lllustrated Corvette Series No.
41 - 1070 Aero Coupe Corvette Show Car
"It's Good To Be Sr. V.P."
Being
the Senior V.P. of Design at General Motors sure had its perks for Bill
Mitchell. The actual car that was made into the "Aero Coupe" was born
as an off-the-assembly line 1968, small-block Corvette. Over the next
seven years the car lived through three incarnations: the "Aero Coupe",
the "Scirocco", and the "Mulsanne." When the car wasn't on-duty at car
shows, it saw duty as Bill Mitchell's personal ride. What a job!
The first thing that Mitchell's Design Staff did was to remove the 327
small-block and drop in one of the new ZL-1, all-aluminum Can-Am
engines. For several years the ZL-1 used an experimental Rochester
fuel-injection unit and an experimental, four-speed Hydra-Matic
transmission. The ZL-1 was awesome, but the four-speed automatic was
replaced with a Turbo 400 unit. And what Bill Mitchell show car
wouldn't be complete without side-mounted exhausts? Mitchell described
the Aero Coupe as a "bear!"
With plenty of power under Bill's right foot, the Design Staff started
work on the body. It may have been slightly overdone, but that's what
show cars like the Aero Coupe were supposed to do. They are
"officially" called "Research and Development Vehicles." The Aero Coupe
had many interesting styling cues. The egg-crate front grille and side
vents were the only design elements that made it into production. The
front end had a deep, "shovel-style" front spoiler that wrapped around
its chin. At the rear, there was a matching, wrap-around spoiler
similar to the '70-1/2 Z-28 Camaro. The side pipe covers were similar
to the optional, production side pipes, except for the section under
the doors that had six groups of vertical scribe lines. The windshield
and roof were interesting. The A-pillars were curved at the top
corners, allowing the glass and roof to have a smooth, continuous line.
The removable roof panel was a single piece and hinged at the back.
Since the car was using Chevrolet's ZL-1, the ZL-2 hood option was
used. And continuing with the Can-Am influence, fat Goodyear tires were
monuted on wide, Chaparral-style alloy wheels.
The interior was very plush for a Corvette. It was completely trimmed
in tan leather and deep-cut carpet. Years later a crude digital unit
was added to the dash that projected the car's speed on to the
windshield.
The Aero Coupe was completed with a deep, candy apple red paint with
heavy gold metalflake, gold striping, and Corvette, and ZL-1 badges.
This very special Corvette went on to delight Corvette fans for 7
years, with each version getting more wild. When if finally became the
Mulsane in '74, only insiders knew that it was really a '68 small-block
Vette on steroids.
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