The 1970-1972 Corvette ZR1


Special Editions: The 1970-72 Corvette ZR1

For many of us, when we hear the designation “ZR1”, we think of the ultra-fast, ultra-powerful C7 Corvette version that was introduced in early 2019.  We might also recall the 638 horsepower, super-charged C6 “Blue Devil” ZR1 that was introduced in 2009, or even the fourth generation ZR-1 “King of the Hill” Corvette that first debuted in 1990.  However, did you know that the earliest ZR1 Corvettes came into existence long before any of these later iterations?  If not, then take a few minutes to acquaint yourself with one the rarest small-block production Corvettes of all time – the 19701972 Corvette ZR1.

1970 Corvette ZR1
The 1970 Corvette ZR1 featured an LT1 small-block engine rated at 370 horsepower and 11.0:1 compression

The third-generation Corvette ZR1 was first introduced in 1970 as the successor to the L88 Corvette.  The car, which could be ordered as Regular Production Option (RPO) ZR1, came equipped with a new, solid-lifter, small-block engine that GM designated the LT1. The LT1 engine, which was manufactured by GM from 19701972,  was a 350 cubic-inch small block that produced 370 horsepower.  It featured 11:1 compression, a ‘178’ high-performance camshaft and a 780 CFM Holley four-barrel carburetor mounted to a special aluminum intake.  Although not as powerful as the L88, the LT1 engine offered consumers an exciting engine platform that could power their Corvettes at and around the racetrack.

1970 LT1 Engine
The 1970 LT1 350CI small-block engine.

In addition to the LT1 engine, Corvettes ordered with RPO ZR1 came equipped with the M22 “Rockcrusher” transmission, heavy-duty power brakes with dual-pin front brake calipers (J56), a transistor ignition, a special aluminum radiator and a heavier-duty suspension package that included bolstered 7-leaf rear springs, shocks and heavy-duty 5/8 inch front sway bars and rear spindle struts/stabilizer bars.   The car also came equipped with metal fan shrouds.  Moreover, when ordering a ZR1, the following options were deleted from the Corvette, including: a rear window defroster (C50), air-conditioning (C60), power steering (N40), deluxe wheel covers (P02), the alarm system (UA6), AM/FM radio (U69) and AM/FM Radio, stereo (U79).

1970 Corvette ZR1 Convertible
A 1970 Corvette ZR1 Convertible

The deletion of these items was intentionally designed to help reduce the car’s overall weight as well as to reduce the power load put on the engine, thereby ensuring that more power was transferred from the engine, through the transmission and to the rear wheels.  In fact, it was impossible to order the ZR1 with any of the “creature comforts” synonymous with the more conventional Corvettes being offered by Chevrolet dealers across the nation. Despite this, the 1970 Corvette ZR1 could be ordered as a convertible!

Although it was more competitively priced that many of the other high-performance Corvettes from that era (the 1969 Corvette ZL-1 for example), the 1970 Corvette ZR1 still struggled to make a connection with most consumers.  The car was well received, but GM has created a culture of “sticker shock” with its high-end variants, and this was no different with the ZR1.  Interestingly, the cost of adding the ZR1 option to the 1970 Corvette was just $968.95 when it was initially being sold to the public by Chevrolet. Despite this, just 25 ZR1 equipped Corvettes were sold in 1970.

1971 Corvette ZR2 Convertible
1971 Corvette ZR2 Convertible

For 1971, Chevrolet offered consumers not one, but two special purpose (racing) packages.

The first of these was the RPO ZR1 package which one more utilized the aforementioned LT1 engine, although the 1971 (and 1972) models  would see a reduction in engine compression from 11.0:1 to just 9.0:1.  Like the 1970 models, the 1971 ZR1 also included a heavy-duty, four-speed, close ratio transmission (RPO M22), heavy-duty power brakes, a special aluminum radiator, a metal fan shroud, a transistor ignition, and a revised suspension with special springs, shocks, spindle-strut shafts, and front and rear stabilizer bars (though it has since been determined that the 1971 Corvette ZR1 has appeared with and without rear stabilizers.)  As before, when equipped with the ZR1 package, consumers were once more unable to include many of the more “luxurious” amenities available, which included power windows, a rear window defroster, air conditioning, power steering, deluxe wheel covers, an alarm system, and any type of AM/FM radio.

The second special purpose package that Chevrolet offered was RPO ZR2. This special purpose package was identical to the ZR1, except that instead of a small block LT1 engine, the ZR2 came equipped with a 454 cubic inch LS6 engine.  Like the ZR1, the ZR2 package also included the same ordering restrictions – namely none of the “creature comfort” amenities that were appealing to many consumers were available with that package.

1972 Corvette ZR1
The 1972 Corvette ZR1 marked the last time that a ZR1 package would be offered by Chevrolet until the introduction of the 1990 Corvette ZR-1 nearly 20 years later!

It may be for that very reason – or perhaps that combined with the substantial cost increase that each option carried with it ($1,010 for RPO ZR1 and $1,747 for RPO ZR2) – that so few of either performance packages was ordered during the 1971 model year.  In total, only eight Corvettes were ordered with the ZR1 option, and only twelve were ordered with the ZR2.

The ZR1 package was offered once more for the 1972 model year.   As with the 1970 and 1971 models, sales of the ZR1 package were extremely limited, totaling just 20 units that year.  Due to increasing emission regulations and an overall lack of sales, the ZR1 Special Purpose LT1 Engine Package was ultimately cancelled at the end of 1972.  During the car’s three year run, only 53 zR1 Corvettes were ever ordered, making the ZR1 Corvettes of the 1970’s one of the rarest small-block Corvettes ever produced!

 

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