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1996 Corvette LT1 Engine Buildup - What Price Performance?

In the first of our LT1-buildup articles, we explore the benefits of going cheap

Jay Heath Oct 11, 2006

Our test subject pauses to catch its breath between pulls. At the end of the day, the car had gained 13 hp and 10.5 lb-ft of torque for a total investment of well under $300.

Contrary to what our predilection for megabuck tuner cars might suggest, we at VETTE are acutely aware that our readership is not composed entirely of professional athletes, real-estate magnates, and other car-crazed croesuses. And while our saturation point for bespoilered quad-turbo street freaks with outlandish DayGlo paint schemes will always exceed that of our colleagues in the auto-mag world, we're not above occasionally making room for a vehicle that represents a more reasoned approach to the modification game.

With that in mind, we've decided to introduce a project that more closely resembles the sort of thing we coupon-cutting types are likely to undertake. Our mission is simple in concept, even if its execution is certain to prove more daunting. We'll be shooting for Z06-challenging accelerative performance-low 12s in the quarter sounds about right-while minimizing our cash outlay and avoiding extraneous (read: non-performance-enhancing) modifications. Simply put, if a part isn't designed to make the car run faster or launch harder, we won't be expending any ink on it here.


Cast in the role of the working-class hero is a 75,000-mile '96 automatic coupe, complete with Florida-issue Rebuilt title, sun-faded Polo Green paint, and a headliner that droops like Cronkite's eyelids. At a sale price of $9,000, the '96 not only conforms to our bucks-down build philosophy, its year of manufacture dictates that it was factory equipped with one of the most underappreciated V-8 engines in the Vette's 53-year history. And while it certainly won't make realizing our e.t. goals any easier, using an LT1 car will give us an opportunity to explore a lesser-known nook of the Corvette aftermarket-and, we hope, to confirm or refute some of the prevailing wisdom regarding the Gen II's potential as a high-performance engine.

For our first round of installations, we decided to focus on the cheapest of the cheap, the idea being to effect a verifiable, if not noticeable, improvement in the Vette's output for the kind of money one might drop on a couple weeks' worth of groceries. All of our installations and dyno tests were performed at Anti-Venom, a Seffner, Florida-based performance shop specializing in late-model Corvettes.


A comparison of the factory air lid and the Breathless piece appears to lend credence to BPP's claims of a 70-percent flow improvement.

Accustomed as we are to 600-, 800-, and even 1,000hp C5s and C6s, we were primed for disappointment when Anti-Venom proprietor Greg Lovell strapped our virgin '96 to the shop's Dynojet chassis dyno for its first pull. We were pleasantly surprised, then, when the car registered a respectable 263.3 horses and 291.5 lb-ft of torque at the rear wheels, not too far off what one might expect from an early automatic C5. After a backup test produced virtually identical numbers, we unlimbered the tools and got to work.

Breathless Performance Modified Air Lid (PN 100-213)
Cost: $59
Gain: 3 rwhp, 3 rwtq

In 1990, Chevy gave the Corvette a new airbox lid equipped with a series of flow-enhancing horizontal slats. Breathless Performance Products' C4 Modified Air Lid does the factory one better by incorporating a fully open-faced design reminiscent of a picture frame. Made of ABS plastic, the BPP lid can be installed in a matter of minutes, with no modifications to the factory box. At a piddling $59, it seemed like a natural fit for our low-lucre outing.


Surprisingly, swapping the paper filter for a K&N had no effect on our dyno results.

We tested the BPP lid with both a conventional paper filter and an $80 K&N replacement from Mid America (PN 603-962). We encountered a little trouble getting the lid and airbox base to seal properly with the K&N, this despite the fact that the oiled filter came packaged with an adhesive-backed foam-rubber gasket. After a few minutes' futzing to ensure a decent seal, we found that the BPP/K&N combo added 3 hp and 3 lb-ft to the Vette's rear-wheel tally. (All of our "gain" numbers are based on a two-pull average.)

Follow-up tests with the paper filter yielded identical results. While 3 horses may not sound like much, the extra airflow provided by the BPP lid is sure to play a more critical role as we bolt on additional performance gear.Had the K&N made more power than its conventional counterpart, we likely could have overlooked its fitment foibles and comparatively high price tag. Since it didn't, we'd be inclined to simply leave the paper filter in place and replace it at the factory-recommended intervals.

Note: Although its price tag prevented it from being included in this ultra-low-buck test, we decided to see how SLP's "Claw" cold-air induction setup (PN 21028) acquitted itself on the rollers. Equipped with three conical filters mated to large-diameter stainless steel tubing, the $267.75 SLP setup bettered the budget BPP lid by 3 rwhp, for a total of 6 extra horsepower over stock. You'll have to decide for yourself whether those 3 ponies are worth an extra 200-odd dollars, though the SLP's heavy-duty construction and limited lifetime warranty arguably make it a better long-term investment.


Mid America's MAF-end assembly eliminates the restrictive "air straightening" screens used in the stock unit.

Mid America Motorworks Mass-Airflow-Sensor Housing (PN 616-002)
Cost: $49.95 (on sale; normally $99.95)
Gain: 9 rwhp, 7 rwtq

Modifying the mass airflow sensor has been a popular practice with backyard Yunicks since the mid '80s. Rather than simply punching out the screens on the OEM unit, we decided to try one of Mid America's Mass-Airflow-Sensor housings, on sale at the time for only $49.95. Comprising two larger-than-stock plastic end pieces that sandwich the factory MAF, the housing is said to move 55 percent more air than the OEM setup, for a total flow rating of 1,000 cfm. Ours installed in around 10 minutes with no unpleasant surprises, and after verifying that the car's idle quality was good and that no SES lights had been triggered, we made our next set of pulls.

We were stunned when the Dynojet registered improvements of 9 rwhp and 7 rwtq-precisely what Mid America claims for the unit in its catalog. That the plastic aftermarket housing is lighter and conducts less heat than the aluminum stocker is an added bonus.

Aside from a forced-induction system or nitrous kit, this may be the first aftermarket part we've tested whose performance actually lived up to its advance billing. Even at its regular price of $99.95, this one's a steal.


While removing the screens has been known to cause rough idling and illuminate SES lights in older-model vehicles, we noticed no adverse effects from the swap.

Breathless Performance Products 160-degree Thermostat (PN 100-214) and Coolant Bypass Kit (PN 100-215)
Cost: $39.98 ($19.99 each)
Gain: 1 rwhp, 0.5 rwtq

Corvettes have long been known for overly warm engine-operating temperatures, and the LT1 C4 is no exception. Ours tended to run in the 200-to-210-degree range in normal driving, occasionally creeping into the 230-degree zone when traffic snarled.

While they were unlikely to make a significant difference in our dyno numbers, we reasoned that a few well-chosen cooling-system modifications should have a salutary effect on real-world performance and engine-component longevity. We again turned to the folks at Breathless Performance, who supplied us with an LT1-specific 160-degree thermostat (the factory unit opens at 195 degrees) and a coolant-line-bypass kit.

The parts went on easily in under an hour and with a minimum of perturbation. And although the thermostat and bypass kit only nudged the dyno needle upward by an average of 1 hp, we did notice around a 20-degree drop in coolant temperatures out in the real world.


BPP's Coolant Bypass Kit reroutes the lines that circulate hot coolant through orifices (shown) in the factory throttle body. The idea is to reduce the temperature of the throttle body itself, resulting in a denser, more oxygen-rich intake charge. It's been suggested that this mod be avoided by enthusiasts who dwell in colder climes, but we've never once heard of a case in which a throttle blade became stuck due to icing.

It's worth noting, however, that this cooling benefit all but disappeared in heavy traffic, a fact attributable to our car's stock fan programming. Indeed, only by complementing the lower-temp thermostat with revised fan-actuation thresholds is it possible to exert complete control over engine-operating temperatures. We'll address this in the near future, when we perform a dyno-based custom PCM tune on the car, but for now, the 20-degree drop under most driving conditions is a welcome improvement.

Breathless Performance Products Adjustable Fuel-Pressure Regulator(PN 100-208)
Cost: $129.99
Gain: 0 rwhp, 0 rwtq

Like modifying the factory MAF sensor, fiddling with fuel-pressure settings has been a popular method for extracting extra power ever since the Corvette graduated to electronic fuel injection in the mid-'80s. Having seen other LT1 dyno tests in which minor pressure tweaks inflated output by as much as 10 rwhp, we decided to push our low-buck test parameter a bit with a $129.95 adjustable pressure regulator from BPP.

After establishing that our Vette's fuel system was providing 47 psi of pressure in stock form, we dialed in a series of 2-psi increases, retesting at each increment until we reached a maximum pressure of 55 psi. Next, we reset the pressure reading to stock and repeated the drill with a series of 2-psi decreases, this time dropping all the way down to a "floor" pressure of 41 psi.


Somewhat surprisingly, none of our monkeying had any positive effect on the output of the engine. Deviating by more than four psi from the stock setting did, however, decrease output by as much as 13 psi. Could it be that by 1996, Chevy had refined the LT1's electronics to such a degree that altering fuel-pressure settings was no longer a viable power-tuning technique? Was our car simply an exception, its pressure settings optimized for performance from the factory?

Notwithstanding our rather disappointing initial results, we suspect that the pressure-tuning capability provided by the adjustable regulator will prove useful as we perform more significant modifications in the future. Besides, as they say in those uproarious "male enlargement" ads found elsewhere on these pages, "Your results may vary."

In the end, our efforts yielded 13 rwhp and 10.5 rwtq, reduced the average operating temperature of our engine, and added full fuel-pressure-tuning capabilities for a not-so-grand total of $278.92. Too dear for you? Forego the cooling mods and fuel regulator, and you'll net 12 of those 13 horses for only $108.95.

H.L. Mencken once said, "The chief value of money lies in the fact that one lives in a world in which it is overestimated." The same applies here. We're just not exactly sure how.


1810 N. Parsons, Ste. 106/108
Dept VM
Seffner, FL 33584
(813) 661-9000

Breathless Performance Products
2070-F Tigertail Blvd., No. 2
Dept. VM
Dania, FL 33004

Mid America Motorworks
P.O. Box 1368
Dept. VM
Effingham, IL 62401
(800) 500-1500



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