The good news about C4 Corvettes is they're easy to find and not all that difficult to wor
One of the biggest unwritten rules with this magazine is we avoid the Corvette. The Chevy market is divided into Corvettes--and everything else. For this reason, as well as the expense issue, we have mostly avoided edit on the plastic fantastic. But we're going to break our own rules for this story, and we'd ask that you set aside your biases and open your mind to a different idea. We're about to take you on a quick flight through what has to be the best deal in performance cars on the planet--the C4 Corvette. For those of you who don't speak Vette, the C4 moniker represents the '84 through '96 fourth-generation cars, and we're going to place our emphasis on the '84 through '91s as being the best buys. Take a quick stroll through Craigslist in your region and we guarantee you can find several examples for less than $5,000. We also came up with this bit of coercion: Pick your favorite car. Let's say for argument's sake it's a '69 Camaro. How much would you have to spend to outfit that car with EFI, independent rear suspension, four-wheel disc brakes, forged-aluminum suspension components, rack-and-pinion steering, an overdrive transmission, 16-inch aluminum wheels, and a host of other goodies all packaged in a car that weighs roughly 3,300 pounds? The answer is you'd spend a hell of a lot more than $5,000. The most stripped-down base model C4 Corvette, regardless of year, has all the above equipment. Some of it may need a little help, and other pieces might be better off taking up residence on the shop floor, but if you strip a C4 to its bare essentials, you have the makings of a kick-ass street/track car. That's what this story is all about.
In 1984, Chevy built more than 50,000 Vettes, so there are plenty to go 'round. We saw thi
The C4 Early Years
The '84's styling was a big-time winner, but history also remembers that first year as a horsepower loser. The first-year Vettes were powered by pathetic 205hp, 350ci engines using the Cross-Fire induction, which was really nothing more than a pair of TBI injectors on top of a split-runner manifold and quickly earned it the Cease-Fire nickname. The rest of the drivetrain was equally lame with a troublesome 700-R4 overdrive automatic or the Doug Nash-built 4+3. This manual trans was basically a BorgWarner four-speed with an automatic transmission-style planetary overdrive bolted to the back that allowed you to select overdrive in any gear except First. All automatic cars got the weaker Dana 36 IRS, while the manual transmission cars were blessed with the stronger Dana 44.
Performance was barely brighter in 1985 when Chevy replaced the Cross-Fire with Tuned Port Induction (TPI), but horsepower was still only 230. The '86 cars were the first to get ABS, and later models did get aluminum heads. The alloy heads reduced weight but really didn't do much for horsepower, which was still marginal at 240. The big change in 1989 was the appearance of the German-built ZF six-speed manual trans, which was a big improvement over the balky 4+3. We'll save the discussion of the '90 ZR-1 DOHC cars for some other time.
Jim Hall at Tuned Port Induction Specialties (TPIS) tells us his ultimate C4 best buy would be the '89 to'91 cars. These TPI engines converted to Speed Density fuel injection, eliminating the quarrelsome mass airflow (MAF) sensor. Even better, Chevy redesigned the suspension beginning with the '88 cars, improving the front suspension's scrub radius. The '89 cars also enjoyed a standard 17 x 91?2-inch wheel with 275/40VR17 tires, a significant step up from the previous years' 16 x 8.5-inch and 255/50R16-inch rollers. If you're looking for LT1 power, these first appeared in the Corvette with the '92 cars.
The bottom line here is that while these cars offered outstanding hand- ling potential, they are less than spectacular when it comes to horsepower. This is what makes them excellent engine swap material for either a stout Gen I small-block or, as we'll see later in this story, a thumpin' LS-series engine.
The Cross-Fire air cleaner hides a terrible induction system that helped produce a measly
This '86 automatic was offered at $3,000, but you probably could have driven it away for $
Just in case you don't know what an aluminum-headed TPI motor looks like, this will help y
Perhaps the first thing we'd do with a stock C4 TPI Corvette is open up the air cleaner as
Let's cut to the chase here. Our goal is to present a few performance-enhancing ideas you can apply to a typical C4 Corvette to unleash the beast and not spend a bunch of money along the way. Some may want to start slowly, using the existing engine and drivetrain, which is fine. Let's start with a typical TPI 350 with an automatic. The classic car crafting mods work with Vettes just like they do with Camaros, including an unrestricted inlet system, an adjustable fuel pressure regulator, headers, an exhaust system with less backpressure, and then perhaps a mild cam such as TPIS' ZZ9 or ZZ409 grinds. TPIS, for example, sells a set of long-tube headers for '84 to '91 cars for around $750 coated, and you'll need a Y-pipe and an after-cat exhaust for another $600--but then the exhaust is done. These prices are a little higher than for a '69 Camaro, but the headers are high-quality pieces that fit. All these basic bolt-ons will also work on the LT1 engines.
One intake modification that received a lot of attention back in the L98 days was the Lingenfelter SuperRam manifold. The problem with the stock TPI intake was the runners were too small and too long for a 350, since the manifold was originally designed for a 305. The longer runners make excellent torque but are all done by 4,800 rpm. Lingenfelter cut the runner length, added a large plenum, and was able to make power right up past 6,000 rpm. Accel still sells this emissions-legal manifold.
While factory aluminum heads might look high performance, they're not nearly as good as ev
Displacement is always an easy way to make more power. An affordable idea is to build a 383 or 408ci Gen I short-block and add a good set of aluminum heads, long-tube headers, and a SuperRam and it's possible to make 450 hp or more and still be emissions-compatible. The SuperRam makes gobs of torque (we've made as much as 550 lb-ft on a 420ci small-block), so the biggest problem is hooking all that power to the ground.
While more horsepower is obviously a major requirement, don't forget that the drivetrains in these early Vettes were somewhat anemic, especially the automatics. If you want to stick with an automatic, then a stronger 700-R4 should be in your plans. But if we were going to build a stout C4 to burn a few street jousters, nothing less than a durable five-speed would make the grade. Thankfully, Keisler offers a direct-fit kit to bolt several different manual transmissions in a C4. Our choice would be the Tremec TKO-600 box with its 2.87:1 First gear and 0.64:1 Overdrive. A stock rear axle ratio of 3.08 makes for a deep First gear ratio, while cruise rpm will be low in Over-drive. Of course, if that idea's too steep for your wallet, then you could always go retro with a Super T10 or Muncie.
Working our way to the rear, if your C4 candidate came with an automatic, then it also has the weaker, Dana 36 rearend assembly. You can swap in a complete Dana 44 with its stronger 8.5-inch rear gear if you can find a suitable donor. But know this: The market is well aware of what these are worth and they are not cheap--but it's the best way to get there.
Suspension and Brake Upgrades
Even the earliest '84 C4 suspension is superior to those in any '60s or '70s muscle car, so right out of the box the Corvette offers dramatic opportunities for a killer track car. But any good deal on a C4 will also include at least 100,000 miles of abuse. The best approach would be a simple upgrade of the existing ball joints and suspension bushings. Along with the suspension rebuild, we'd go with at least Bilstein replacement shocks, or you could upgrade to full-race double-adjustable shocks from QA1 or Koni, for example. Then there are the more exotic modifications that we can save for a later date, but all these simple mods will only improve handling for a relatively minor investment.
The Accel SuperRam manifold is a bolt-on for any Corvette TPI engine and pushes the peak h
Brakes are the other big modification you can make, although even the lowliest '84 C4 came with 12-inch front rotors (11.5-inch rear) and a decent PBR caliper. You could also step up to a Vette Brakes & Products C5 conversion that bumps the rotors to 13 inches and C5 calipers, but this will also require 17-inch wheels, which isn't a bad idea anyway. In fact, that 17-inch wheel and tire upgrade should also be a requirement if you plan on attacking the local road course with this package. And why wouldn't you?
LS Motor Swaps
Here's where it gets fun. Sure, you can bolt a hot Gen I small-block into a C4 and go fast--that's been done. Let's talk about boosting the C4 into the 21st century with an LS-series engine. The swap isn't that difficult, and there are a couple of companies that offer parts. This is a great idea whose time has come. Consider an all-aluminum LS1 or LS2 engine with 500 hp that's also going to pull 150 pounds off the nose of a car that is already at 3,000 pounds. Combine that with a TKO-600 five-speed trans that is durable and light and you have a killer combination in a car that now weighs around 2,900 pounds (minus driver). That's an easy 12-flat car on the dragstrip at around 117 mph. Think about dusting some clown in a C6 who thinks he has the baddest act in town. He'd have to call for an emergency meeting with his therapist.
We talked to Dave Emanuel, who swapped an iron 5.3L LS engine into an '87 C4 Vette he bought for $3,000. This entire conversion is detailed in a series of stories in our sister magazine Corvette Fever. Emanuel also installed a Tremec TKO-600 five-speed, retaining the C4's stock hydraulic master cylinder. You can peruse this series online at corvettefever.com. Speed Hound Performance in Georgia offers both custom engine mounts and a set of Melrose-coated headers for this conversion that combined will run about $900. You'll also need a Corvette-style accessory drive to clear the steering on the C4. These accessory drives can be expensive, but you can also go with a Kwik Performance conversion for just the alternator and power steering for $287. We outlined this kit in a previous LS-series engine accessory drives story ("LSx Accessory Drive Swap Guide," May '09). You might also want to get rid of that cheesy digital dash that the early C4s came with. A company called VettAid is marketing a nice analog gauge package that plugs right into the stock C4 wiring harness.
For a killer road rocket, the best swap is to bolt in a Tremec TKO-600 trans. You can piec
You can find complete, used Dana 44 rear axle assemblies if you search long enough. We fou
The stock Corvette comes with forged-aluminum control arms and a camber curve intended for
Factory C4 12-inch discs are plenty good for most applications, but if you're going to tak
Swapping an LS-series engine into a C4 Corvette will require motor mounts and headers but
These are the Melrose-coated headers and the engine mount plates that take a Napa motor mo
We found this '03 iron 6.0L engine and 4L80E automatic at the swap meet. Combine this $2,5
|Keisler Automotive||Speed Hound|
|Engineering||Social Circle, GA|
| ||Street Legal Performance|
|Melrose Headers||Toms River, NJ|
| ||Tuned Port Induction|
|Mr. Gasket (Accel)||Specialties (TPIS)|
|Cleveland, OH||Chaska, MN|
| || |
|Fort Worth, TX||Social Circle, GA|
| || |
|Rock Auto||Vette Brakes and Products|
|Madison, WI||St. Petersburg, FL|