1995 Chevrolet Corvette ZR1 - The Purple Project

C4 Adventures On The Road And Under The Hood

Hib Halverson Nov 1, 2001 0 Comment(s)
Vemp_0111_01_z 1995_chevrolet_corvette_zr1 Vette_handling 2/9

Part 6: We Take Time Out to Go FastOne-hundred-five miles per hour on a back road at 1:30 a.m. and closing on a Porsche? Uh-huh. That's the stuff really good Corvette stories are made of.

Cibie 130-watt high-beams bored a bright hole in the night as we rocketed east on Highway 119. We were about 13 miles northeast of Taft (get a Southern California road map. Look southwest of Bakersfield) and a couple of clicks west of Interstate 5.

To test "Barney," our Dark Purple Metallic '95 ZR-1, we were running "Starlite," the premier "map-type Monte Carlo" rally in the western U.S. This wasn't just any Starlite, either. It was the final event. Starlite had run annually since 1971 on the second weekend after Thanksgiving, but later this morning, 30 years of tradition would end. I was proud to have run many of them since entering my first in 1975. As usual, I entered as car number 13.

Always a ball-buster, this rally runs 14-1/2 hours, mostly over back roads through Southern California and Southern Nevada. It starts at 8:00 p.m., Friday, in Goleta, a suburb of Santa Barbara, the northern jewel of the Southern California coast.

Starlite 2000 first took us over the coastal mountains behind Pismo Beach, some of the best twisties in the state. From there, it crossed the southern end of California's San Joaquin Valley, went over the Tehachapi Mountains, across the Mojave Desert, skirted the southern end of Death Valley, and into Nevada. Most of this was at night, and it ended in the Las Vegas area about 11:00 the next morning. There were nine checkpoints for Regular Class competitors like us and another five for Expert Class cars. The total mileage for Class R-if you ran the course right-was exactly 608.6 miles.

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After blowing the Porsche into the weeds and running across California's lower San Joaquin Valley, we got to Standoff 9, where Navigator Peterson takes a compass bearing on the Inmarker.

At 105 in Sixth gear, the car's four-cam, 32-valve, V-8 was turning about 2,300 rpm. At that throttle opening, the Flowmasters weren't "purring;" a better word might be "throbbing." Even at 2,300, the LT5 exhibited raw power. Seeing the I-5 bridge in the high-beams, I lifted, maybe 10 mph, then shot over the interstate. What did a sleepy, northbound trucker think as he saw something a little slower than a meteorite flash overhead?

Down to Fifth. Up to 105 again. Then, back to Sixth. I could see we were catching other rally cars. The first was a Jaguar XJ8 sedan, loaded with a crew of three and destined to win Starlite overall-in spite of the big Jag puking its trans at the rally's end. I passed the XJ8 to find a second Jag, an S-type sedan, ahead. Didn't take too long to get around him, either.

Another quarter of a mile and we came up on a Porsche 930 Turbo rolling along at 95 or so. Like a P-51 pilot approaching an unsuspecting ME109 from six-o'clock, I dimmed my lights, slowed a bit, and took a spot about 80 feet behind. Suddenly there was a puff from the Porsche's exhaust and he picked up speed.

I shot a glance at my longtime Starlite navigator, Gary Peterson, looked back at the road and said, "Dude, I been wantin' to do this for years." I downshifted, Sixth to Third, floored it, drafted right up to the Porsche's spoiler, then pulled out to pass. We blew by the Turbo at 6,500. I pulled 7,000 in third, grabbed Fourth and held it to almost 6,000, saw 130 on the speedo, lifted and shifted to Sixth. Ain't four cams grand?

"I think we made our point!" Gary shouted.

Way ahead of the Porsche, we backed off to 105 and rolled along Route 119, across 10 miles of deserted farmland east of the Interstate. We did speed limits through little towns like Old River, Panama, and Pumpkin Center, then crossed Route 99, the second of the Valley's two big North-South highways, heading through the farms southeast of Bakersfield.

Vemp_0111_03_z 1995_chevrolet_corvette_zr1 Superior_headlights 4/9

"Map-type Monte Carlo events" sometimes have fast night driving. For that, you need superior headlights. We used Cibie E-code lights from Stern Lighting. They bolt into the stock C4 headlight buckets and seem to work well with the later C4 wiring.

A little after two, we parked at the "Standoff Point" for Leg 9 near the corner of Bena and Caliente-Bodfish Roads in the hills east of Bakersfield. In spite of the unimaginative name (from linking the foothill village of Caliente with the town of Bodfish, deep in the Sequoia National Forest) this steep, windy road is infamous in Starlite lore for its challenge to drivers and navigators alike. I'd run it on at least two Starlites before this. While Gary got out and did his navigator thing-observing the checkpoint and discussing it with other members of our "Equinox Rally Team"-I idly looked at the map and saw a mountain east of us called "Nellie's Nipple." Only in California.

Purple Project Prep
The decision to take Barney on Starlite was made in haste. A Vette is not always my pick in rally cars. Although I've run it three times in Corvettes, twice in Firebirds, and once in a Chevy Beretta, my primary rally car is a hot-rod '65 Malibu station wagon. No doubt that's got you laughing your butt off, however, the "Blue Bullet" works pretty well. Seventies big-blocks, Porsche 911s, and, most recently on Starlite '97, a BMW 5-series, have all felt the agony of defeat during impromptu "contests." A properly set-up C4 is a much better car, but running the old wagon in a sports car rally better suits my "attitude problem." Sadly, the Malibu had a driveline problem that couldn't be fixed in time for the final Starlite.

Three weeks before the event, Gary and I prepared the Purple Project. Starlite runs at night and we'd use the car's lighting systems with the engine off, so we needed a new battery. The project came to us with the lower capacity unit used on L98 and LT1-4 cars. LT5s, because of an 11:1 compression ratio, need more starting power. We installed an ACDelco Professional Car and Truck Battery (PN 75-7Y), which is the most powerful one that fits a C4.

We also had to fix the car's leaking front shock absorbers. A problem, unique to Selective Ride Control shocks on cars with RPO FX3, can be premature failure of the shock's inner shaft seals. FX3 was on all ZR-1s, all Z07s, and some other '89-95s. If you have liquid oil residue on the upper shock mount that appears to seep from underneath the SRC actuator assembly on the top of the shock, you have this problem.

Vemp_0111_04_z 1995_chevrolet_corvette_zr1 Shaft_seal_problem 5/9

A front FX3 Selective Ride Control Bilstein shock. The black thing on the top of the shock is the actuator. If an SRC shock has the shaft seal problem, oil will leak from underneath the actuator.

The piston rod assembly in these shocks is two concentric shafts. The outer doubles as the piston rod and, at the bottom, half of a sleeve valve regulating oil flow bypassed around the main valve stack. The inner shaft's lower section is the other part of this valve. The top of the inner shaft is splined to the SRC Actuator. To vary the shock valving, the actuator turns the inner shaft. As it rotates, the bypass opening varies. The larger the opening, the softer the shock valving. The smaller the opening, the more firm the valving.

The seal between the two shafts can be problematic. When it fails, oil is forced up through the space between the shafts and out the top of the shock. Leaking SRC shocks can be repaired by Bilstein Corporation of America-in fact, a new piston rod assembly with more durable inner shaft seals was released last year. The charge for repair is less than the price of new shocks. I pulled all four off and sent them to Bilstein for rebuilding.

Bilstein also has a revalving service. Aggressive street drivers, autocrossers, or road racers can improve the handling of FX3 cars by revalving their shocks at the same time they're rebuilt. They offer several valving configurations, including one that works for street/track cars like the Purple Project. Valving in all six SRC ranges is stiffened, with the low ranges changing moderately and the upper ranges significantly. Additionally, the rears get a substantial increase in rebound, which helps the ZR-1's tendency towards drop-throttle oversteer.

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Barney on Nevada Highway 160 through the Red Rock Canyon area west of Las Vegas. We were on our way to the Checkpoint 16, the final Inmarker of the final Starlite Rally.

The revalving had a dramatic effect on the car's handling. In the lower SRC ranges, the wheels were more aggressively damped. The floating effect of the soft OE rebound control is gone. I occasionally autocross and the stiffened, upper SRC ranges offer better control during aggressive maneuvering at low speeds. Revalving noticeably improves the car's response in transient maneuvers. The change in rear rebound, alone, is worth the cost.

We needed new tires. Performance enthusiasts are often concerned with a tire's ultimate dry traction, however, for an event like Starlite; you need to be concerned with other issues, too, mainly traction in bad weather. During winter in California, weather in the mountains can vary from snow and ice to warm winds.

Obviously, we couldn't use any of the low tread-depth, sticky compound "fair weather" tires. We needed something with good performance in the dry and the wet. Choices in replacement tires for the unusual 315/35ZR-17s used at the rear of ZR-1s is limited. I've used Goodyear Eagle F1GSs on my old Malibu, but it's not available in 315/35. We looked at the Michelin Pilot Sport, a tire with great wet traction and 315 availability, but they were out of stock at the time. The Goodyear Eagle GS-C was OE on all '92-96s. Its design dates to the early-'90s so it, admittedly, lacks the cutting-edge technology of the more recent F1GS, F1 Steel, and new F1 Supercar. Nevertheless, GS-C is still a reasonably good tire when dry traction, wet performance, predictability, and tread life are of importance. We ordered a set of GS-Cs in the stock ZR-1 sizes.

We had the wheels aligned at So-Cal Speed Shop in Pomona, California. So-Cal's Jim Sleeper set the alignment at: -0.5 degrees front camber, 6.0 degrees caster, 0 front toe, -0.25 degrees rear camber and 1/32-inch rear toe-in, per side. This is a good "compromise" alignment that improves handling but does not extract a severe cost in tire wear. Regular C4s, lacking the big back tires can use a quarter degree more negative camber at the rear.

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Some C4 fans lower their cars. This not only improves handling but makes Corvettes look better. However, use moderation when lowering a car used in rallies like Starlite. You'll be running at 7-8/10ths over unfamiliar, secondary roads. You want a car that handles well, but also has adequate suspension travel so you can fly around a blind turn, be surprised by a big dip or railroad crossing ,and not severely bottom the car. For that, you need aggressive shocks and adequate suspension travel. The Purple Project is lowered only 3/8-1/2 inch.

For night performance driving, bright headlights are required. The cheap, plastic, stockers are woefully inadequate. Even the Hella, DOT-approved replacements I'd previously installed are marginal for rally work. My solution was Cibie, 7.5x5-inch, "E-Code" replacement lights with optional 130/100-watt bulbs. Cibie does not distribute in the United States, so you must buy them from importers like Daniel Stern Lighting. The last mechanical prep was to check fluids, install a fresh set of ACDelco Rapidfire #9 spark plugs, and set the tires at 35 psi, cold.

Rallies require a highly-accurate, digital timer. Navigator Gary Peterson installed that on the dash above the DIC using Velcro and a specially-cut block of sponge rubber. We wired it to the car's accessory connector under the console box. We added my Valentine One radar warning receiver, a CB radio, a cellular phone, a hand-held spotlight (for finding street signs at night) a three-cell Maglite, and a set of Nikon Tundra 10x50 binoculars.

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Jim Sleeper works the So Cal Speed Shop alignment rack. He's verifying the -0.25 camber he's just dialed into Barney's rear suspension.

Rally Basics
Starlites were "map-type, Monte Carlo rallies," named for the maps entrants use and that they mimicked Europe's famed Monte Carlo Rally. They are segmented in legs, each with two way points: "Standoff Point" and "Inmarker". Entrants get a package of official maps and route instructions specifying the elapsed or "true" time for each Leg, the Standoff Point location, a vague location of the Inmarker, and the direction you must travel when passing them. Three facts are missing: Inmarker location, the Leg's correct route, and the distance between Standoff and Inmarker. The skill test comes in solving those mysteries so that you pass the Inmarker at the correct time.

Rallyists choose their route and speed from the start of a Leg to the Standoff where a stop is required. The Inmarker area is visible from the Standoff, though the Inmarker itself and the road it is on might not be. The Inmarker can be a few hundred feet or miles away. At night, Inmarkers display a flashing light. Observation of the Inmarker from the Standoff helps, so getting to the Standoff with a time margin is advised. Some rallyists take compass bearings on the Inmarker. Those actions, along with careful map reading, experience and intuition, local knowledge and assessment of time left before in-time can help solve the Inmarker intrigue but, occasionally, they don't. Sometimes you just have to take a wild-ass guess.

Once you leave the Standoff, with limited exception, you may not stop until you pass the Inmarker. If you do, you're assessed a maximum error for that Leg. Most entrants allow plenty of time to get to the Inmarker. You might creep the last few hundred yards, slowly crossing the Inmarker at the right time and earning the coveted "zero" error. Creeping, a time-honored rally tactic, is not always possible. Some Inmarkers have a minimum crossing speed, which makes the challenge even more interesting.

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Just before sun-up, on Highway 127, 44.5 miles north of Interstate 15 and a little east of Death Valley National Park, we found Standoff 14.

The Inmarker ends one leg and starts the next. The time you cross it is recorded electronically. Early or late, you are penalized one point for each hundredth of a minute error in arrival. Some checkpoints are timed to the thousandth of a minute for tie-breaker situations. Your total score is the sum of all legs' errors. Why are rallies timed in hundredths or thousandths of a minute, rather than in seconds? It's just another quirky tradition in the sport of rallying. Maximum error per Leg is five minutes. If you miss an Inmarker by more (which happens when entrants get lost or otherwise fall victim to a rallymaster's trickery), take a "max" and go straight to the next Standoff.

An "entrant" is a driver and a navigator. It was once allowed to run Starlite solo, but the practice was later outlawed. I knew a guy who ran Starlite alone, a colorful rallyist named Ed Morgan. One of Ed's quirks was his rally cars used interceptor units he bought at California Highway Patrol auctions. One year, 1976 I think it was, his navigator stiffed him the afternoon of the event, claiming some awful sickness. Ed, wild man that he was said, "Screw it. I'll run the rally alone." He was car #2 that year and the #1 DNS'ed, so Ed didn't even have another rallyist to follow. The heavy workload of driving and navigating had him late to many checkpoints. Veteran Starlite workers tell of an early morning inmarker on Highway 178 outside of Inyokern, where a sleepy checkpoint worker was awakened by a sudden roar and opened his eyes as a Dodge Polara literally screamed by. Morgan had his foot all the way in that 440 Dodge, which was just about redlined in high gear, so he was running about 140. It took a quarter mile to stop that hulking cop car. When Ed finally backed up to the checkpoint, the wide-eyed worker simply said, "Whoa, no navigator. Man, you are hardcore," and gave him his time-the error was only a few hundredths.

Obviously, with all this timing, map reading, figuring, deducing, and, sometimes just plain guessing, navigators find Monte Carlo rallies a challenge. The navigator is the key to a win. They must: be good with maps and figures; have an uncanny sense of direction, location and time; be able to take notes, figure distances, read maps and timers in a moving vehicle; and trust their driver implicitly. A good rally navigator is a precious commodity. Typically, driver and navigator run many events together. My navigator, Gary, is a previous Starlite winner (1986 with a different driver) and we'd run the last eight Starlites together.

A well-written Monte Carlo rally can be a stimulating experience for the driver, too, because great rallymasters pick roads that entice one to probe their vehicle's performance envelope.

Back on Leg Nine
When they wrote Leg 9, Starlite 2000 Rallymasters Keith Horton and Jim King must have been feeling a little devious-or maybe they just like Caliente-Bodfish Road. It was darn lucky we ran hard to get to the Standoff, because my navigator needed time to consider the Inmarker location along with conferencing with other members of the Equinox Team.

Nine was what rallyists call a "loop," and it was almost a double-loop because the Expert Class cars would run part of it a second time going to Inmarker 10, not part of the R-Class instructions.

Gary estimated if we ran 30 mph from the Standoff to Inmarker 9, we'd arrive there with a zero. So, about 20 minutes before in time, I fired the Purple Thing and off we went. We continued east on Bena Road, past the intersection of it and Caliente-Bodfish. A few minutes later we crossed State Route 223 and began paralleling SR 58. After driving along Bena a little longer, we noticed other rally cars stopped half a mile or so ahead.

"Oh, s***," I hissed, "The damn checkpoint. How could it be so close?"

"Creep." Gary answered with a puzzled look on his face. I slowed to where the engine was idling in first gear. "Go slower," Gary added.

Creeping can sometimes burn up a minute or two, but no way could we creep-off 10 minutes or so this close to the marker with the last eighth-mile uphill. I wasn't going to fry a clutch, even for Starlite: The Final Event. I decided we'd take the error. I stayed idling in first gear. We crossed way early and drove up to the rally workers parked just beyond the marker. When we handed them our time card, they told us they were 10, not 9.

The joke was on us.
We'd taken the wrong route and stumbled across the Expert-only Inmarker 10. Later, in conversation with Co-rallymaster Horton, I learned we should have been over on SR 58. All was not lost. We'd used some, but not all the time we built up with our run across the San Joaquin Valley.

We left Inmarker 10 at high speed, turned left on Bealville Rd., slowed to 30, crossed the Southern Pacific Railroad, drove a couple of miles, then turned left again on Caliente-Bodfish Road.

"Speed up again." Gary ordered, looking at the timer and the map.

I accelerated to 40. Half a minute later, after more map study, he said, "Uh, you'd better haul ass. We're close to in time and I don't see the marker or any cars. It's farther than I thought."

I flicked the SRC selector to "perf," felt the Bilsteins stiffen, backshifted to Second and accelerated hard. Now I was going about as fast as any talented-but-safe performance driver would want on an unfamiliar windy road at night. I was using Second gear hard-twisting the motor to 6,500-6,800 rpm each time. On straights I got into Third gear. In left turns where I could see ahead, I apexed in the oncoming lane. Though we might have been looking at a big error on this leg, no way was I discouraged. With the joyful noise of the LT5's unsilenced intake and Flowmaster exhaust, coupled with near road race driving, I was having a blast. This was exactly why I own a Corvette.

As we burned up curvy Caliente-Bodfish, still hoping for a zero, we hit a couple turns so tight I went down to first, then was on it hard enough to see the "ASR Active" light at the exits. In situations like this, most '92-up C4 drivers despise Acceleration Slip Regulation ("traction control"), but the combination of the engine's extra power and stock ASR calibration made the system less invasive than on a production car. It had just the right effectiveness to make it an ideal traction aid in driving like this. I left ASR on, drove the car, foot-to-the-floor, off turns and let it control wheel spin.

After several minutes, we charged around a bend to find Inmarker 9 and a couple of cars creeping a few hundred feet ahead. I braked to ABS, coasted past one car which should have been behind us, then established a creep to get us across the marker on the zero. After all that effort, I actually misjudged the last 50 feet or so before the hose and we were 0.01-minute (six tenths of a second) early.

I guess I was too pumped-up. After rounding that last turn hard on it, then going from high speed to almost no speed in seconds, I lost concentration.

Nevertheless, we were happy with the "oh-one" error. The car's outstanding performance was a textbook solution to several problems: 1) we took the wrong route on part of the loop and 2) misjudging the distance between Standoff and Inmarker 9.

So, How'd we Do?
We had a three error going into 9. Leaving it with an "oh-one," we followed with a string of ones on the next three Legs. We arrived at the final Standoff of the final Starlite with a seven. Inmarker 16 was one of those where the SBSCC timed both sets of wheels, meaning, to zero the leg, both axles must cross within the same hundredth. That forces a crossing speed up about 30 mph. Wouldn't you know it-I choked, big time. We were 19 (a little more than 10 seconds) early.

We ended with a 26 error, which would net us fourth place in Regular Class, my personal best as a rallyist and a pretty respectable finish. At the Starlite 2000 banquet that night, Gary and I received the Best in Club trophy for the Equinox 10-car entry. That award goes to the best finishing team entrant that didn't otherwise trophy.

How'd Barney the ZR-1 do?
We couldn't have asked for more. The Automasters Street Skinner engine ran flawlessly. The chassis modifications we made prior to the Starlite made the car faster and easier to drive in the rally environment.

We'd like to thank the Santa Barbara Sports Car Club's Starlite Organizing Committee for 30 years of great rallies. We're sorry to see them end, but you guys did it right and went out heroes. We'd also like to thank all of the Purple Project sponsors for their support. It made our performance in Starlite 2000: The Final Event possible.


Bilstein Corporation of America
San Diego, CA 92121,
Daniel Stern Lighting
Ann Arbor, MI 48105


Come take a ride with us in the night as we take out a dark purple metallic 1995 Corvette ZR-1!
Hib Halverson Nov 1, 2001


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