Project C4orce-finally on...
Project C4orce-finally on the road. After countless delays, we finally have a running '87 Corvette powered by an LS-style engine and a state-of-the-art five-speed transmission. Unfortunately, the paint scheme is an obvious indication that this isn't a typical C4-otherwise a rap on the gas pedal would really leave many C5 and C6 owners scratching their heads.
A long time ago, in a magazine far, far away, we built a Corvette project car designed to incorporate a state-of-the-art powertrain with a C4 chassis. It came to be known as Project C4orce, and it progressed with little more than standard project-car delays and frustrations. To a point. Then Mr. Murphy and his law ("Anything that can go wrong, will go wrong") stepped in with a vengeance. Suffice it to say, once "Darth Murphy" appeared, "The Force" was definitely not with us. I'll spare you all the gory details that led to one delay after another, and move on to the final chapter, after a brief recap.
The original series launched in Corvette Fever magazine, which was merged into VETTE earlier this year. Our plan was to update an '87 C4 with an LS-based powerplant and a five-speed Tremec transmission, and to spend less than $15,000 (including the cost of the car) to complete the project. It's certainly possible to do that-if you're not trying to serve the dual masters of project completion and editorial coverage. Obviously, anyone attempting to duplicate our project will have to address issues unique to the vehicle with which they're working. In attempting to cover as many of these issues as we could, it appeared that our budget was spinning out of control. In fact it wasn't, because many of the modifications we made were not required by our particular project vehicle; we included them because it was reasonable to expect that they would be required on other C4 project candidates.
Installation of the powertrain...
Installation of the powertrain was handled by Trey Hanson of SpeedHound Performance (now a part of VettAid). The 5.3-liter engine looks perfectly at home in a C4 engine compartment. Hanson had special adapter plates made to make installation a drop-in proposition. The LS engine is in approximately the same position as the original L98, so front/rear weight distribution is virtually unchanged from original specifications.
As can be seen in the accompanying photos, Project C4orce was ultimately "dressed" with a unique paint scheme designed by Murray Pfaff of Pfaff Designs in Royal Oak, Michigan. Complementing the paint is a set of C6-style Sport Edition V6 wheels and Dunlop Sport 9000 tires from the Tire Rack. Interior upgrades include unique C4orce leather upholstery and plush carpeting by Mid America Motorworks, along with an analog instrument panel from VettAid.
Beneath Project C4orce's hood is a 5.3-liter LS-style engine that spent its former life in a Silverado pickup truck. Our initial decision to use this mill, as opposed to an LS1 or LS2, was prompted by economics. We purchased a complete engine, including all accessories, PCM, and wiring harness, for $700. Some readers criticized this choice as being a step backward because we were replacing a 5.7-liter (L98) engine with one of less displacement. The point that these readers missed is that if we had made no modifications at all to the 5.3, we still would have picked up 45 horsepower (the factory ratings for the 5.3- and the original 5.7-liter TPI engines are 295 and 240, respectively).
The session at Atlanta Chassis...
The session at Atlanta Chassis Dyno was a real eye-opener, as the C4orce engine cranked out 349.75 horsepower. Considering the relatively mild cam and minimal engine work, we didn't expect the engine to put out almost 50 hp more than a stock LS1.
With surprisingly few modifications, 5.3-liter engines can crank out enough power to bring a smile to the face of any Corvette owner. But before a "truck" engine can be installed in a C4 chassis, a few changes have to be made. On the top side, the relatively tall truck intake manifold and high-mounted accessories will poke large, ugly holes in the hood, should you attempt to close it. On the lower end, truck-style oil pans are much too deep for a Corvette's low stance. The easy solution is to install an LS1 or LS6 intake and an accessory bracket, water pump, vibration damper, and oil pan originally designed for a C5 or F-body (Camaro/Firebird).
That's precisely what we did. We also added a set of 1 3/4-inch, coated tubular headers from Melrose Motorsports that were specifically designed to fit LS-style engines installed in C4 chassis. The balance of the car's exhaust system consists of a Random Technology high-flow catalytic converter/X-crossover pipe assembly. This system, which is also available for L98- and LT1-powered C4s, is a true dual system that extends from the header collectors to the mufflers. This arrangement allows virtually any muffler originally designed for a C4 to be used. We added a pair of stainless steel mufflers that provided a deep tone and aggressive sound.
Melrose Motorsports offers...
Melrose Motorsports offers a super set of headers designed specifically for an LS-series engine installed in a C4 chassis. The headers feature 1 3/4-inch-diameter primary tubes and ceramic coating. The motor-mount adapter plates can be ordered separately, or as part of a conversion-header package. These parts can also be used with C3 conversions.
We used EFILive's FlashScan...
We used EFILive's FlashScan software to monitor and tune the PCM. The handheld unit can perform these functions on its own, or it can be connected to a laptop computer. Custom leather upholstery from Mid America is visible in the background.
Random Technology's converter/X-crossover...
Random Technology's converter/X-crossover system converts '84-'91 exhaust systems to true duals. Front adapter pipes (not shown) connect the headers to the "X" and are available for conventional small-blocks as well as LS conversions.