Project Nissan Silvia: Part VI

If you've ever worked on a car before, you know these projects are never as simple as they should be. This goes double for anything built to a magazine deadline. There are always countless details that are either left out, or figured out after the story goes to press. Here's a little catch-up, then, on the dirty details we've never told you about Project Silvia. Don't think that just because they didn't fit in previous installments they aren't important, either. We're talking little details like "how to make your brakes actually work," and "how to keep your wheels from falling off."

Seats
Here's a little detail: how to find a seat that doesn't smell. If you think we've been basking in the aroma of a 277,000-mile driver's seat all this time, you're not as smart as we thought. Not only were they odiferous, the factory S13 seats are so poorly shaped, we would have been flung out the window on our 1.0-g skidpad test if we still had them. In reality, we solved the seat problem way back in part 1 of this project (November, '02) but had so much other stuff to tell you about, we never actually mentioned it.

Finding seats for an S13 is far from trivial. Not only is headroom severely limited, but the floor is an awkward shape, with a massive hump under the driver's right knee making seat mounting particularly difficult. Most aftermarket seats are so thick once sliders and an adaptor bracket have been installed, that unless your friends call you stumpy, you won't be able to fit in the car.

The R32 and R34 Skyline GT-R had the same issues and mostly the same floorpan. If you're extremely lucky and happen to find a GT-R owner dim enough to sell you his seats, buy them. Three of their four mounting points line up, and the fourth can be made to work fairly easily. The GT-R seats are better than nearly anything you'll find in the aftermarket, and since the donor car was right-hand drive, you'll get to sit in the seldom used, and less worn, passenger's seat.

Barring that stroke of luck (we scoured two countries for a year and a half before we lucked into a single R32 seat at Spriso Motorsports) you'll need something aftermarket. Luckily for us, the solution was right there at our suspension shop. JIC USA happens to offer a seat with a very slim bottom section, and mates it to a cleverly designed bracket and rails that put it right on the floor. The adaptor bracket itself is only about a quarter-inch thick, with a countersunk mounting bolt used over the offending floor hump to save a few millimeters of clearance. Even this wouldn't be enough, but JIC pushed the right-hand seat rail over to the middle of the seat, avoiding the floor hump altogether. This puts the two rails very close together, which allows the seat to rock back and forth a fair amount if you grab the back rest and shake it. This lends an air of cheapness to the car much like, oh, a Z-06 Corvette. Yeah, floppy seat backs don't really ruin that car's reputation, either.

The JIC reclining racing seats are generously bolstered and have an adjustable backrest, but don't flip forward for backseat access. Even when you crank the seat forward manually, there's limited rear-seat clearance, since the massive side bolsters collide before the seat is very far forward. What is this, a taxi? Who cares about the backseat?

The JIC seats will fit you best if you have the classic broad-shouldered, narrow-waisted physique of a superhero, or perhaps the barrel chest and atrophied legs of a barfly. If you sport a twiggy backside, you'll find the side bolsters a little far away. If, on the other hand, you're packing more than 32 inches of waistline, you may find the nougens a little restricted by the bottom bolsters. It's an odd shape for a Japanese seat, considering there are no Asian members of the Justice League, but it ends up working perfectly well. The seats have provided ache-free comfort for several 1,500-mile road trips, as well as sufficient support and (barely) sufficient helmet clearance for more than a few giant-killing track days.

Headroom is nearly identical to the Skyline or stock seat.

Making the brakes work
After installing the Brembo Gran Turismo 300ZX front brake kit and Z32 300ZX rear brakes back in part 1, we pointed out that a bigger master cylinder would really be needed to get proper Brembo pedal feel. We also complained of premature rear-wheel lockup and somewhat average 130-foot stopping distances from 60 mph.

The diameter of the master cylinder determines both how much brake force you'll get for a given pedal effort, and how much pedal movement there will be. The stock 7/8-inch master cylinder has a piston area of 0.60 square inches, so 100 pounds of force shoving on the piston from the combined effort of your foot, the pedal lever ratio and the brake booster, will make 167 psi (100 lb/0.60 in2) of fluid pressure with which to squeeze the calipers. Moving to a 1-inch master cylinder gets you 0.79 square inches, which makes only 127 psi from the same 100 pounds of footwork.

Since we had complained that the brakes felt touchy and overboosted, this reduction in pressure would be exactly what we needed. We also complained that there was too much pedal movement. The bigger master cylinder helps here, too. A 7/8-inch cylinder moving 0.1 inches pumps .060 cubic inches of fluid to the brakes. A 1-inch cylinder would pump .079 cubic inches. That means it would take less pedal movement to move the brake pads the fraction of an inch from their resting position to the rotors.

Checking the Nissan parts books, the Z32 300ZX shares the 240SX's master cylinder design, but comes in 1-inch and even 1 1/16-inch sizes. Wanting a big change in pedal feel, we went for the bigger cylinder (part number 46010 30 p21) This would increase pedal effort by 65 percent. (The 0.99-square inch bore would make 101 psi at 100 pounds of pedal force, or need 165 pounds to make the same 167 psi the stock cylinder made at 100 pounds.) Since the bigger cylinder pumps 65 percent more fluid for the same stroke, it would also significantly reduce pedal slop.

Nissan has always used two suppliers for its brake hydraulics, Nabco and Tokico. The part number we listed is for the Nabco part, but be sure you're clear about what you want or the dealer may substitute the Tokico part. Though the parts are functionally identical, they aren't exactly the same. The 1 1/16 master cylinder only came on cars with ABS, and those cars only needed two brake lines from the master cylinder--one for the front wheels and one for the rears.

Non-ABS cars had three lines, one for each front wheel, and one for both rears (it was split into two at the rear of the car). ABS cars had the extra front brake line port plugged, but here's the difference. On the Nabco cylinders, a simple hex-key plug is used, so an Allen wrench can be used to remove it. After that, the 240SX brake line goes right in. The Tokico cylinder, though, uses a five-sided plug. We were only able to remove the plug after hammering an oversized TORX socket into the five-sided hole.

That's when we discovered the second problem. The hole is machined for a Volkswagen-style bubble-flare brake line, not the standard Nissan reverse-flare. In other words, if you get the Tokico cylinder, be prepared to fabricate some brake lines.

As a final bonus, the brake proportioning valve is built into the master cylinder. Since the Brembo kit was designed around a Z32 master cylinder, proportioning valve and rear brakes, using this master cylinder completes the brake system well. In practice, the front wheels now lock before the rears--a major improvement.

Longer wheel studs
To prevent the front tires and front springs from occupying the same space, we use 5mm spacers behind the front wheels. The spacers push the wheels farther from the hubs, but the wheel studs stay where they are. In our case, this left only about 4.5 turns of thread engagement on the lug nuts. This is not good.

A good rule of thumb if you don't want your wheels to fall off is to have the thread engagement be at least as deep as the stud is wide. Nissan studs are M12x1.25, which means they are 12mm in diameter, and each thread, or each turn of the lug nut, is 1.25mm. To have 12mm of thread engagement, you need to be able to turn the lug nut 9.6 times before it's fully torqued.

To accomplish this, we bought a set of fiendishly expensive Nismo long wheel studs. Installing new wheel studs is quite easy. Just remove the caliper and rotor, thread an ugly old lug nut onto the stud, and whack the living hell out of it with a hammer. Depending on your level of anger, it should pop out with a few taps. Slide the new stud in from behind the hole, pull it relatively straight and try, by feel, to line up the splines with the grooves left by the old stud. Now, to pull it into place, you'll need a spacer, or a stack of washers, and a lug nut. Lube the threads with some anti-seize paste, thread the lug nut on until it hits the spacer, and tighten it like crazy. The stud should pull in smooth and straight.

Making the tach work
If you start with an '89 or '90 240SX, the tach won't work when you install the SR20DET. The reason is simple: The 1991-and-later cars, including all the SR20-powered Japanese cars, used a lower voltage tach signal. The early tach doesn't even notice the later signal. The solution is even simpler: use a later tach.

That sounds like a pain until you try it. Pull the instrument cluster out and pop all the plastic clips holding it together until you have all the gauges swinging in the breeze. Now, the tach is held to the cluster with three screws. These screws also double as the signal inputs, so there are no wires to unplug. Just unscrew the old tach and screw in the new one. We used the tach from our front clip, which had side-by-side speedo and tach, and put it in our earlier, center-mounted cluster. The tach is a hair larger, so we had to trim one corner of it with a pair of scissors. That was it. It worked.

The stripes
OK, so the Krylon commando was in a show. That means it needed stickers, right? So we put black stickers on the black car and to our amazement, nobody can figure out how we created this amazing effect. It's a flat black car. The stickers are just two shiny black BRE stripes with all the logos cut out of them, which lets the flat black show through. How did we do that? We called Imagine-It Graphics and said, "We need black BRE stripes this tall with these logos cut out of them." Then they said, "Here you go." Then we said, "Thanks."

No spray paint involved.

Previous Installments
Hybrid How-To: May 2002
Engine swap, JDM bodywork

Part I: November 2002
Wheels, tires, brakes, suspension, five-lug hubs

Part II: June 2003
Disco potato turbo, intercooler, exhaust, engine management

Part III: September 2003
Shooting for a 12-second quarter mile. Quaife differential, drag tires, clutch

Part IV: October 2003
Dialing it in: Whiteline anti-roll bars and making the right adjustments to pull 1.0g and run a 12.9-second quarter mile with the same setup

Part V: January 2004
Keeping it cool: New grille and a homemade intercooler sprayer for $3.08