C3 Corvette Exhaust
Article by Mark Trotta
Corvettes produced from 1968 through 1974 have true dual exhaust: there are left-side and right-side engine pipes that pass through left and right "tunnels" in the transmission cross-member. These years were the only true dual exhaust for C3 Corvettes.
Starting in 1975, in order to comply with EPA (Environmental Protection Agency) regulations, all cars sold in North America required catalytic converters. Corvettes from 1975 through 1982 were fitted with "2 into 1 into 2" exhaust systems.
1975-1979 Corvette Exhaust
The 1975-1979 Corvette exhaust system is made up of six pieces. A front Y-pipe connects the left and right manifold, which goes to a single outlet. A small pipe connects it to the front of the catalytic converter.
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Catalytic Converter
When in good working order, catalytic converters do not rob power from an engine. An inexpensive EPA certified converter for 1975-1981 Corvettes is Walker #15037. It has a stainless-steel body and no air tube. Inlet and outlet are both 2-1/4" and are a pipe-to-pipe fit.
The Walker 15037 Cat is sold as a universal fit, so some minor modification is necessary. It is not legal for sale on vehicles licensed in the state of California.
At the back of the cat is the rear Y-pipe, which splits under the differential carrier and goes to the left and right mufflers.
Exhaust Manifolds
From 1963 through 1980, all small-block Corvettes came with cast-iron exhaust manifolds. While efficient at quieting exhaust noise, they were heavy and held heat near the motor.
In an effort to save weight and be more fuel efficient, GM engineers developed tubular stainless-steel manifolds, found on 1981 and up Corvettes. Although similar, 1981 and 1982 exhaust manifolds carry a different part number.
1980-1982 Corvette Exhaust
For the 1980, 1981, and 1982 Corvette models, the exhaust system is made up of five pieces. A front Y-pipe connects the left and right manifold, which goes to a single outlet. This connects directly to the front of the catalytic converter. At the back of the cat is the rear Y-pipe, which splits under the differential carrier and goes to the left and right mufflers.
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The 1981 and 1982 Corvettes are computer-controlled and are optimized to function with the converter in place. Removing the converter, along with the O2 sensor, confuses the computer and will likely cause the car to run worse.
1982 Corvette Exhaust System Replacement
My old 1982 Corvette needed a complete exhaust system from the manifolds back. The converter was missing when I got the car, and there was nothing but a single straight pipe running to the back of the car. No mufflers, either. Not only did it sound awful, the car never would have passed state inspection. (U.S. Federal law makes it illegal to remove or disable any emission equipment on a street-driven vehicle.)
The only exhaust piece I couldn't get locally was the front Y-pipe. A stainless-steel Y-pipe is offered from Mid-America. The rest of the exhaust system came from a local parts house.
A direct-fit converter for 1982 Corvettes is Walker 15618, which also fits later (1984-1991) Corvettes. It has a stainless steel body and is sold as a direct-fit replacement for 1982 Corvettes (universal for others).
The Walker 15618 inlet and outlet are four-bolt welded flanges. It is not legal for sale on vehicles licensed in the state of California.
Several hangers and muffler clamps were needed as well. There is a center exhaust hanger bracket, and left and right muffler hanger brackets. Also installed was a new oxygen sensor, which screws into a bung on the front Y-pipe. An air-tube kit Walker #35574 is required to install the Cat.
The rear Y-pipe is a Walker #40477, and the left and right rear mufflers are #22160 and #22161.
The exhaust system was installed at a friend's shop on a lift. There wasn't much left of the old system to take off, so that saved us time. Replacing the complete exhaust system took about two hours.
Note: If you're replacing exhaust manifolds and not concerned about 100% originality, a good upgrade is to use stainless-steel studs. Lightly coat the threads with anti-seize compound before installing.
C3 Corvette Side Pipes
Side exhaust pipes are all about the look and the sound. If you don't like LOUD, don't even consider side pipes for your Corvette!
Factory-style Corvette side-pipes will correctly fit 1968-1974 models. Please note that side-mount exhaust pipes have their pros and cons. Do some research on C3 Corvette side-pipes before going this route.
NOTE: C3 Corvette side pipe kits do not come with a provision for an oxygen sensor, which 1981 and 1982 models had. If you do not re-install the sensor, you'll likely encounter spitting and sputtering from the engine. Adding one to an aftermarket exhaust system would require welding an 02 bung onto the engine pipe.
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