ZR1 Factoids
The ZR1 "Special Purpose Engine Package" cost $968.95 - almost 20% the base cost of the car. The package consisted of the LT1 engine with a lightweight flywheel and high-torque starter; M22 HD close ratio four-speed manual transmission; F41 suspension comprising special 89lb front springs, 121 lb rear springs, matching shock absorbers and .75" front stabilizer bar; J56 HD Brake Package with power assist, dual-pin front calipers and semi-metallic brake pads; HD (high-capacity) Aluminum radiator with overflow tank; HD Positraction rear end; and various parts left over from the previous model year's high-performance parts bins. The only "options" available when ordering the special-purpose engine package were the deluxe interior and tilt/telescope steering column. Power windows, power steering, air conditioning (like all LT1's), radio, rear window defrosters and PO2 wheel covers were not available with RPO ZR1. The C3 ZR1's are essentially an L88-prepped chassis, fitted with a slightly modified LT1 rather than the 430hp 427.
* The Special Purpose Engine Package was a different assembly from the standard LT1 engine available in its civilian brethren, hence the different suffix codes assigned to call out the non-standard parts required. Although the internals, intake and exhaust were identical to the standard LT1, the CTV suffix code in '70 (and the CGY in '71 and CKZ in '72) were fitted with a 10.5" light weight L88-style flywheel and corresponding #403 bellhousing as well as a high-torque L88 ('69 coded & dated) starter with aluminum nose.
A powerful small-block may...
A powerful small-block may not have the grunt of the bigger Corvette engines, but nor does it carry massive front-end weight: the whole car is significantly better balanced. The current carb is temporary but a date-code-correct smog system (pump, hoses, clamps, etc), 1100884 alternator and corresponding very rare Holley 4489 NA9 carburetor (California LT1 cars only) is restored and ready for installation.
* The ZR1's low build numbers prompted the use of small batches of special heavy-duty parts. These parts are often date-coded exactly the same, even if the build dates of the cars are months apart. This has turned out to be a dependable way of authenticating purported ZR1's.
* The ZR1 was the last GM production vehicle to come with the factory disclaimer warning: "Not intended for normal driving situations."
* The 1970 model year production was postponed until January of that year making it the shortest model year run of the Corvette in history.
* The ZR1 Engine Package option was not mentioned in GM literature until well into the model year run. This suggests that those who ordered the cars were either connected with organized racing, or knew the right people to place the orders.
* There were reports that early cars featured the L88-style cold air induction hoods, but this has never been substantiated.
* A few of 1970's performance-minded Corvette buyers most likely ended up with a ZR1 when the 465HP LS7 Corvette engine option was pulled from production at the last minute. The ZR1's were the next "hottest" Corvette available if you intended to go racing.
* The ZR1 used a different (beefier) shock mount than other, non-F41 equipped Corvettes.
* All ZR1 rear deck panels were originally drilled for a radio antenna because most Corvettes were ordered with radios. The ZR1s and "radio delete" cars had the hole filled on the assembly line.
* In an attempt to sandbag horsepower numbers to obtain lower insurance ratings, the LT1 engine was rated at 370hp. It's generally accepted the solid-lifter mouse motor's factory output is closer to 400hp, and can easily be increased by adding headers and a little performance tuning.