1986 C4 Corvette Solo 2

This is the Corvette that Dave Hill and his Corvette engineering staff don't want to know about. The C4s, built from early 1983 (as an '84 model) 'til mid-1996, were former chief engineer Dave McLellan's creation, while Hill gets credit for the '97 and newer C5s. Some folks inside at GM have told us that McLellan deserves more credit for the C5 than he's been given, but that's another story entirely.

Autocross, or Solo 2 in SCCA, is a unique form of competition. You have to drive around on an artificial course that's usually set up in a giant parking lot. You're racing against the clock, not against other cars, and a lap lasts less than a minute. If you think of an autocross as a qualifying lap in racing, you're pretty close. There's no chance to relax and very little opportunity to think about what you're doing. 

Driver ability and a good handling car are the important things for winning in autocross. It also helps for your engine to have a lot of low-end torque and to be hooked to a solid-shifting automatic transmission. When you're driving through cones on narrow courses, wide cars and long wheelbases are hindrances to getting the best time. Early ('84-90) C4s are 176.5 inches long and 71 inches wide on a 96.2-inch wheelbase, while C5s are 179.6 inches long and 73.6 inches wide with a 104.5-inch wheelbase. The same width and long wheelbase that makes a C5 roomy inside and exceedingly stable at high speeds makes it awkward and unwieldy on a tight and twisty autocross course.

The old '85 to '87 Corvettes seem to rule the autocross courses around the United States. These old C4s flat beat everything that's come out of Chevrolet since the mid-'80s. When you look at the SCCA National Championships, you'll always find some of these old torque monsters in the standings.Roger Johnson's yellow '86 is one of the best of these unbeatable autocross Corvettes. It's so competitive that a couple years ago some members of the Corvette engineering team invited Roger and his '86 to the Milford (Michigan) Proving Grounds so their boss could see a real, winning autocross Corvette. Some of the team thought it might be useful if they could get a handle on why this old C4 was able to blow away the brand-new C5s. Of course, it blew away the new Corvettes, right on Chevrolet's home turf.

This yellow '86 is a legend amongst the autocross fraternity. While no one is sure if it's the driver or the car that is great, Johnson's driving ability is something that every Corvette owner who's ever run an autocross aspires to. On the other hand, most autocrossers would like to have his car.

There are several reasons that the '85-87 C4s make wonderful autocross cars. The old L98 just can't be matched for bottom-end torque-it'll damn near pull stumps out of the ground. The LT1s, LT4, LT5s, LS1s, and LS6s are all great horsepower engines, but each and every one of them lacks the raw low-end grunt of the old Tune-Port Injection 350. Fifteen years of technology has produced some great engines, but none of 'em can match the low rpm power of a well-tuned L98.

Roger's car, which he bought brand new, only has about 5,000 miles showing on the odometer. The first thousand or so was on the street. The rest is a lot of Solo 2 runs, a whole lot if you consider that the average run is usually well under one mile, and lots of times closer to a half-mile.

In late 1987 the folks at Chevrolet convinced Roger that the new '88 Corvette with its re-designed, zero-scrub-radius front suspension would be the way to go. He even put the yellow beast up for sale while he prepped a new '88 version. Roger was serious about the '88's prep, so the car was sent to C4 performance guru Kim Baker for special attention. The late John Lingenfelter was made sure that all was perfect within the engine.

There was only one problem. The brand new 1988 Corvette couldn't match the times of the old '86. Nothing that Roger did would make the '88 Corvette competitive with the yellow '86. If Roger Johnson, Kim Baker, and John Lingenfelter's combined expertise couldn't make the '88 run as fast as the older car, all hope was gone. Fortunately, no one had come up with the required cash to purchase the "old car" so the "For Sale" signs were taken off the '86 and placed on the '88. It was back to Old Yellow.

Roger has tried C5s but feels that they have major limitations for competitive autocrossing. A great many other Corvette autocrossers apparently agree with him, as you seldom see a C5 at autocrosses, other than Corvettes-only events. Some have tried, but few have succeeded, except with Z06s, at the SCCA level of competition.

The one thing that Roger Johnson has proven is that if you start off with the "right" car, stick with that car, and develop it, you can have a winner. While most of us try the latest trick part of the week, or maybe even the trick car of the month and stay also-rans, Roger just keeps running up the miles on his old yellow '86, and keeps right on winning.

Here's an interview that someone else did with Roger Johnson. Very interesting. He talks about how all of his Corvette engines were blueprinted. 

This article was originally published in Vette magazine around 1999.

Safe Seating

If your seat breaks up in a crash your belts and roll cage are totally useless. Your seat is the primary element in your safety system. A lot of effort has gone into both the design and the materials used to create new, and safer, seats. It’s no longer about the look. It’s all about being safe in a crash.

There are two items of concern. First, we have the issue of the seat itself. Then we have the issue of how this seat is mounted. Even the best seat is useless if it rips out of the floor. One thing is not more important than the other. A great seat does no good unless it’s mounted correctly.

In vintage racing a great deal of attention is paid to the construction of the roll cage and the age of the seat belts. When it comes to seats too many sanctioning groups allow just about anything that looks nice. A brand new 6-point harness won’t do you much good if your seat breaks up in a crash. The various sanctioning groups need to start paying more attention to seats.

Certification

It’s really easy to check on seats. There are two possible certifications. First we have the FIA certification. The FIA Institute is an international organization with the goal of improving motor sport safety. The other certification is from the SFI Foundation. That’s an American based group. There’s no reason to use a seat that has never been tested by one of these organizations.

FIA: One of the current FIA standards is 8862-2009. This certification is required for the World Rally Cup. It’s extremely rigorous and probably not necessary for most of us. Very few seats meet this standard. A much more common standard is the FIA 8855-1999 certification. This specification, along with the date the seat was manufactured, should be found on your seat.

FIA requires that seats be replaced ten years from the date of manufacture. Some sanctioning groups have even stricter requirements. Porsche Club of America requires that the seat be replaced 6 years from the date of manufacture. Some of our vintage organizations need to consider this rule. Most groups have a mandated life span for seat belts but no requirement on seats.

SFI: The SFI Foundation is a non-profit American organization established to issue and administer standards for racing equipment. The SFI is very involved in seating safety. If your seat has passed the SFI certification tests it’ll have a sticker stating both the test it passed and the date of certification. The most recent standard is 39.1 and that’s what NASCAR will be requiring for 2011.

The SFI 39.1 specification means that when the seat is mounted according to the manufacturer's directions the seat cannot deflect more than a given amount and will rebound to the original position. The 39.1 specification calls for less than .250 of an inch of deflection with 4,000lbs of load at the hip; 3,000lbs of load at the shoulder and 2,000lbs of load at the head.

Another SFI specification is 39.2. Once again the test assumes that the manufacturer's mounting specification are followed. The seat cannot deflect more than .500 of an inch and has to rebound to within .250 of an inch with 3,000 lbs of load at the hip, 2,000 lbs of load at the shoulder, and 1,000 lbs of load at the head. These relaxed requirements are used for short track racers who can’t afford the $13,000 seat used by NASCAR.

There is also an SFI specification for the foam used in your seat. It’s covered under SFI 45.2. The critical thing is how rapidly this material compresses and rebounds in the case of an accident. In addition the fabric should also be fire retardant. The FIA requires that the seat meet ISO standard 3795 for flammability.

The Materials

You have some choices here. One isn’t better than the others.  There are quality seats made from aluminum, carbon fiber, Kevlar and fiberglass composites. Each of these materials has a different set of attributes.

Fiberglass: This may be the most common seat material used in vintage cars. Most of the seats are not simply fiberglass but a fiberglass composite with significant strength. These composite seats are economical to manufacture and also lightweight. Even though these composite seats are FIA approved NASCAR outlawed fiberglass seats in 1992. They’re still used a great deal in vintage racing. 

Any number of composite fiberglass seats meet the current FIA requirements. These are good seats and work really well in most vintage cars. The only disadvantage is they tend to be heavier than an equivalent seat made from carbon fiber. Another issue is that some sanctioning bodies require that fiberglass seats use a back brace that’s attached to the roll cage. A lot of drivers would rather not have that brace so they use the carbon fiber seat. FIA does not require a back brace with carbon fiber.

Carbon Fiber: This is very common and it’s used by a huge number of manufacturers. Besides the lightweight there’s an advantage in that this material has a memory. This means you get improved protection in secondary impact. Remember that a crash is normally not just one event – but a series of events that happen very rapidly. Carbon fiber seats have a significant weight advantage over and equivalent seat constructed of fiberglass composite material. A Sparco Evo seat in fiberglass is 19 lbs. The same seat in carbon fiber is 12.6 lbs. You have to decide if 6 lbs is important enough to justify a doubling in cost.

One rather troubling situation is that a number of seats are being made in China that fail to meet normal specifications for carbon fiber. Creating seats out of carbon fiber is rather complex and sophisticated operation. There always companies ready to short cut these processes and put an inexpensive seat into the market. You see these on eBay and the price seems really great. Keep in mind that just because someone says a seat is carbon fiber doesn’t insure your safety. Look for the FIA certification sticker on the seat.

Kevlar: Kevlar seats can be built to meet the FIA safety standards. Cobra has an extensive line of Kevlar seats. Cobra claims a thirty per cent weight reduction over an equivalent fiberglass seat. Since both types of materials can be manufactured to meet FIA standard 8855-1999. It comes down to a matter of how much money you want to spend to save a few pounds.

Aluminum: At one time aluminum was the overwhelming choice for seats. There are still a number of people who believe it’s the best choice. The two biggest suppliers of aluminum seats today are The Joie of Seating and Kirkey. The LeJoie seats meet the SFI standards. They haven’t been subjected to FIA testing though. Europeans have a very strong preference for carbon fiber, Kevlar and fiberglass composites.

At one time aluminum was the standard race seat for almost every sanctioning group in the United States. The aluminum seats are fading from the market. That doesn’t make them bad seats. There is just a lot of competition from other materials. Keep in mind that neither the SFI nor the FIA makes a recommendation regarding seat materials. Both groups are simply concerned with performance in a crash.

Hans Compatibility

There’s a lot of research going on now with the interaction between all of the various safety requirements. You want optimum interplay between your HANS system, the harness system and your helmet. You have to think of this as a total safety system. No single item is going to be useful unless it coordinates with the rest of your system. That’s one reason to find a good supplier and not just order randomly from various web sites.

One way to do this is to make sure you talk to the folks who make all of this safety equipment. They’ve given a lot of thought about how your helmet interacts with your Hans system, which interacts with your harness system all of which interacts with your seat. I believe in the future the seat and harness system will be one integrated unit. That’s already happening at the highest levels. Look for it to filter down to our vintage cars. In this type of seating system the driver is essentially ensconced in a capsule.

Installation

Having a good seat is the first part of the equation. The next part is installing it correctly. It’s paramount that the seat be bolted rigidly to attachment points that are not likely to fail in the event of a crash. The most common way is to bolt the seat to the floor. This usually requires the use of side brackets but each case is unique. Walk around the paddock and look at how different people are installing their seats. Even better ask the tech folks with

your sanctioning group for installation advice.

Mounting the seat back to the cage is one of these items that vary from one sanctioning group to the next. If you have an FIA approved seat you probably won’t be required to use a rear seat brace. The FIA does say though “If the seat is configured for 6-point mounting, an upper seat-bracket must also be provided for the test.” I think they’re telling us to use a rear seat brace.

Also, if you install a new seat you’ll probably need to reconsider the position of the seatbelt anchor points. These should be directly aligned to the force/loads they are intended to take and should have swiveling anchor brackets at the attachment points on the body or cage.

All of this means you need to talk to two every important people. First, check with the tech people in your sanctioning group. Ask them about what seats are approved and what they’re going to be looking for in a mounting system. Next, contact a couple of different manufacturer’s and ask them for a recommendation.

Once you’ve selected a seat that meets the current safety standards you have two more issues to deal with. Will you actually fit into the seat? Now, if you can actually fit into the seat will the seat fit into your car? Most vintage cars have a narrow area for seat placement. This is why you need to deal with an experienced supplier. 

Again, ask about mounting instructions. We used to spend a lot of time talking about roll bars and cages. We’ve come to accept them as part of the hobby. Now we need to think about the science of seating. You can’t enjoy this hobby if you’re disabled from a crash where your seat collapsed. Remember, no one ever plans on crashing. You can though spend some time thinking about what might happen if you do crash.