Imagine the plight of all those '85-'91 Corvette owners who have poured their pride and passion into their Vettes' perfect presentations, only to be stymied by the severe power deficit of the TPI L98 engine. As they hold on to old-and-tired technology, newer Corvettes whiz by them with their Gen III and Gen IV small-blocks. The owners of these newer Vettes look so confident and happy with all the power at their command.
But with the C4's value ranked the lowest among the six generations of Corvettes, many owners of these beautiful stuck-between-classic-and-late-model cars find themselves in a genuine predicament. They don't want to spend a king's ransom to make their cars perform, but they don't want to be left out of the horsepower wars, either.
In this month's quest to find a C4 that addresses both these issues, we tracked down one Corvette owner who was able to swap out his car's long-in-the-tooth L98 for a cammed-up LS1. Even better, he did the entire project for less than $5,000.
"I bought my '87 Corvette in 1997; it was a one-owner car and it gave me a lot of joy at first," says Steve Hardy, a maintenance supervisor in Brandon, Florida. "As the newer Corvettes got faster and faster, I had to make my C4 keep up-not only in speed, but in looks, too."
Hardy added mods as he could afford them, starting with a Toledo Pro 2-inch high-rise hood, a Greenwood-style rear spoiler, an ACI chin spoiler, taillight and parking-light blackouts, and ZR-1 polished wheels. Inside, he replaced the Saddle interior with custom red/black leather seat covers, black door panels and carpet, a painted console, and a custom-stitched console lid. He retired the digital dash in favor of an Auto Meter Pro Comp gauge set-including speedometer, tachometer, oil-pressure, water-temperature, voltage, and fuel readouts-which he mounted in a custom-made diamond-plate dash bezel. For better braking, he added C5 calipers and C6 rotors in the front, along with drilled-and-slotted rotors in the rear. The car's original 3.07 gears were swapped for a set of cryo-treated 3.73s, while the stock suspension was dropped 11/2 inches.
Hardy wasn't afraid to push the L98 to its limit, either. He installed a ProCharger P600B 8-psi supercharger and a Holley Stealth Ram TPI intake, which allowed him to reach his output goal of 340 horses-albeit with a permanent caveat. "The TPI cars have a burn-chip [E-PROM], and it makes them nearly impossible to tune. Every day, I'd have to wonder about what was going to go wrong with the engine system next. The car was no longer fun for me to drive," he says.
Through DigitalCorvettes.com, where he is an administrator, Hardy got in contact with a forum member who wanted out of the hobby and was willing to offer the deal of a lifetime: two complete-but non-running-LS1s; a plethora of C4 parts; an extra box of LS1/6 intakes, coils, and miscellaneous parts; and even a complete 700-R4 rebuild kit. The buy-in price: $750.
"When I got home, I realized all these parts had great potential, but I didn't know what do to do next," Hardy says.
That's when he turned to Greg Lovell of AntiVenom in Seffner, Florida, a Corvette speed specialist. "I looked at the two LS engines. One had come from a very-low-mile wrecked '98 Corvette; it had a cracked block, but the internal components were in like-new condition," says Lovell. "The other came from a '99 Corvette; it had internal damage, but its block was unaffected. I knew that if I took the block from one and the crank, rods, pistons, and heads from the other, I could easily put together a monster-running LS1. The only new parts [Hardy] would have to purchase would be rings, seals, and gaskets. That meant the cost to him would be insanely cheap."
Though a stock early LS1 is rated at an impressive 345 hp, Lovell suggested increasing its output to 425 hp with an AntiVenom Eliminator 2.5 cam. (The specs are confidential, but Lovell was willing to admit that it's based on a 115 LSA and gives the engine a sinister personality.) Other components utilized during the build include a ported LS6 oil pump, a VMAX Motorsports ported 90mm throttle body, an LS6 intake, and an LS7 timing chain. The cost of the build, including parts and labor: $1,100.
"That was all I was willing to spend," Hardy says. "I asked Greg, 'How easy would it be for me to install the engine myself?' He said it would be easy, based upon my technical background, and if I needed any advice, he'd be happy to help."
Lovell's first suggestion was a set of Speed Hound Performance motor-mount plates specifically designed to transplant an LS-series engine into a C4 Corvette. They were a no-brainer for their $100 investment, and Lovell promised that they would make the L98-to-LS conversion go smoothly.
Though the LS1 fits within the C4 engine bay without any modification, Hardy notched two places on the firewall after test fitting-one on the driver side for header-bolt access and the other on the passenger-side firewall to allow extra clearance for the head.
Next, he installed a '90-'96 factory-style slanted radiator and shroud to accept a stock C5 air bridge, which he paired to an AntiVenom airbox. He then bolted on a set of Melrose LS-conversion long-tube headers (17/8-inch primaries), which he mated to the Vette's existing exhaust system (a parts mishmash comprising 3-inch stainless-steel pipes, an X-style crossover, Random Tech cats, and no mufflers).
The wiring conversion was simple, too, thanks to an $800 custom-made harness from Current Performance Wiring in Port Richey, Florida. It allowed him to hard-wire the main and ignition power, the A/C and ECM signals, and the check-engine light, and to use GM-style plug-and-play connectors to power the LS1's myriad electronic connections (MAF, starter signal, O2 sensors, knock sensors, coil packs, et al).
Connecting the LS1 to the Vette's 700-R4 automatic transmission was the next task. Hardy says he found a super-simple solution: elongating the mounting holes on the Corvette's C-beam and sliding the trans forward about 1/4-inch. Then, he bolted a custom 3,600-stall lock-up torque converter to the 700-R4 bellhousing.
Hardy admits that he had a wee bit of stagefright before he inserted the key in the ignition for the first time. "I had never done an L98-to-LS1 conversion before and didn't know what to expect. When I hesitatingly turned the key, the new engine responded instantly and filled my ears with its tailpipe symphony," he says.
Six seconds later the performance ended when the LS1 mysteriously shut off. "I was ecstatic that the engine had roared to life, but completely baffled why it wouldn't stay running," Hardy says.
Lovell at AntiVenom had the answer. The GM ECM (a $90 eBay find) that Hardy installed featured a vehicle anti-theft system, or VATS, that had forced the engine into shut-down mode. "I went to his house with my laptop and turned off the anti-theft system. It hasn't given him any worries since," Lovell says.
Since the project's completion, Hardy has enjoyed his low-buck, LS-powered C4 as a weekend toy, all without the worries that plagued his old blown TPI setup. Of course, there are a lot of different ways to spend $5,000 on a C4. Was it worth it to put the funds into an LS swap?
"There's a huge difference between the new LS1 engine and the supercharged L98," Hardy says. "I keep asking myself why I didn't do the conversion much earlier. The LS engine gives me the peace of mind that I can turn the Corvette's ignition key at any time and never have any nagging concerns about what could go wrong.
"As far as the foot-to-the-pedal experience, there's a world of difference there, too," Hardy concludes. "The blown L98 had a limited powerband of 2,500-4,700 rpm, but the LS engine comes on strong at 1,500 and pulls right up to 6,000. If I could go back and do it again, I'd swap the L98 for an LS engine as quickly as I could. If I ever own another performance-based C4, it won't be without an LS of its own."