The Moment of Truth

The Moment of Truth

Call every car friend you have and get them to look at your installation and find your mistakes before you start the car. Meanwhile, you should be adding octane booster to that 87-octane crap you were running in the KA24.

Fire it up. When that doesn't work, your friends can help you diagnose it. If you need a wiring diagram for the Silvia, we found scans of the diagrams and much of the Australian service manual on www.silvia.hl.com.au.

When ours finally ran, we immediately set out on a 400-mile midnight drive through the most desolate twisty two-lanes in California. Stupid? You bet. But it was also inspirational. Despite tired shocks, blown bushings and an inescapable stench, the Silvia shows amazing potential. Blowing through a tiny stock exhaust, the engine makes far more torque than power and turbo lag is far worse than it should be, but it still cruises effortlessly at triple digit speeds and shows handling balance that rivals the much smaller Miata. This one will be a giant killer.

Body

Body

Of course, you can do this swap with the stock bodywork, but we preferred the look of the Silvia front end, and especially preferred the 24 lbs. we removed from the nose of the car. Swapping the bodywork is very straightforward, but there are a few things you need to note. You need to remove the pop-up headlights first to access all the bumper mounting bolts. Several bolts on each side hold the bumper and front fenders together. Once the bumpers are removed, the fenders come off easily.

When installing the Silvia parts, there are two vertical headlight support brackets in front of the radiator that need to be replaced with Silvia brackets, so be sure you get these with the body panels. Our front bumper came from a non-turbo Silvia, so we also had to cut an intercooler duct. Luckily we were able to trace the stock duct shape from a damaged turbo bumper, cut out a template, and trace the shape onto ours. To cut the holes, we used a hole saw and then ground away the plastic with an electric die grinder.

Wiring

Wiring

You have two basic choices to make your new SR20DET run. The simplest is to use the harness and ECU from a Silvia or 180SX. Once again, your life will be easier if you have a front clip to pull parts from. If you can't get the harness and ECU and you have a harness from a 1991 or later U.S. car, it's possible to convert a U.S. harness and ECU to run the SR20.

Unfortunately, the SR20DET uses a direct coil-on-plug ignition system with four coils, and U.S. ECUs are only capable of driving a single coil. The Japan-only non-turbo rear-drive SR20DE uses a single coil and distributor that can used on the SR20DET, if you can find one. Once this distributor is in place, Jim Wolf Technology can reprogram the ECU for the new engine. A few of the crank angle sensors and coil wires may have to be moved, but JWT has detailed instructions for this change.

Because we had a front clip, of course, we used the Silvia ECU and harness. The harness obviously plugs into the engine, but because of the switch from right-hand to left-hand drive, the harness tries to place the ECU at the driver's feet. Apparently, if you don't mind sloppy harness routing, it's possible to simply twist and stretch the harness into place in a left-hand-drive car. We took a more complex, but ultimately far more sanitary approach.

All our harness work was left in the capable hands of Ralph Kenyon, the Northern California Silvia enthusiast who guided us through most of this swap. He unwrapped most of the harness, laid it out on a board that already had the proper wire lengths marked out on it, started cutting and lengthening wires appropriately. Having done this harness conversion enough times to justify making the board, he has also salvaged enough wires from other harnesses that he was able to lengthen the wires using the exact same wire. Unless you want to send your harness to him, you'll have to use the engine compartment as your board. (Kenyon will convert JDM Silvia harnesses for a fee; his e-mail address is SPRISO_SILVIA@hotmail.com.)

Start by unwrapping the main stem of the harness from the firewall grommet to the area where the injector leads fork off. Plug in the injectors, temperature sensors, idle air bypass, knock sensor and crank angle sensor wires and lay the main stem along the back of the firewall so the firewall grommet can sit in the hole where it belongs. You'll now see the wires to the A/C compressor, power steering pump, mass airflow sensor, O2 sensor and the five wires to the igniter need to be lengthened. If you're shy about lengthening the igniter wires, simply mount the igniter closer to the harness, but we preferred to use the stock mounting location and stock bracket. By the way, if you have a missing or damaged igniter, a '92 or later Infiniti Q45 igniter, part number 22020-50F00, is a direct replacement.

The O2 sensor wires and the mass airflow sensor wires are both shielded, and should be lengthened with shielded wire as well. Any large electronics supply store should have suitable wire. Once everything is the right length, simply rewrap the harness with electrical tape and whatever wiring loom you prefer.

The remaining complication with the Silvia harness is two connectors in front of the battery tray. Apparently, Nissan has standards for which color wire it used for different functions, and what kind of connectors it used, but when the wiring harness teams designed the U.S. and Japanese harnesses, there was no common standard for which pin on the multi-pin connectors each wire should go to.

Several wires therefore have to be swapped around in each of these two connectors to make them match the U.S. connector. A small tab holds each pin in to the connector, and if you depress that tab with either a special pin removal tool or a shaved-down paperclip, you can remove the pin and relocate it. Simply rearrange the wires so the colors match (red wire to red wire, green wire to green wire, etc.).

There are only two tricky parts in these connectors. On the car side of the brown connector, there are two brown wires. You want to connect the outer one to the brown wire on the engine side of the plug. On the engine side of the grey plug, both the black/red and the blue/red wire need to be connected to the black/red wire on the car side of the connector.

Finally, the white connector under the dash needs its pins rearranged to match the car and the wires need to be lengthened slightly.

Mounting the Engine

Mounting the Engine

Installation is the reverse of removal. No, really. At this point, the SR20 should simply bolt in. The SR20 and KA24 use the same engine mounts, so use whichever are in the best shape. Remove the shifter (you'll need snap ring pliers), bolt the transmission crossmember to the transmission mount and lower the whole thing into place. Once you have the engine mounts in place and bolted down, simply raise the transmission into place and bolt the crossmember to the car. The U.S. driveshaft should slide right in.

Now is a good time for new fuel hoses and a new fuel filter. You should also consider upgrading the fuel pump. The stock fuel pump, if it's in good shape, will support the stock SR20DET, but a tired pump or an increase in boost could be trouble. We're saving the pump upgrade for our first round of upgrades.

The JDM radiator, fan shroud and hoses should be used if possible. If you have to use the U.S. radiator, the radiator outlets will be in the wrong place. A few 90-degree radiator hoses and a length of aluminum pipe make an easy crossover pipe. With a U.S. radiator, you'll need to switch to electric fans, since the stock fan shroud won't fit. If, like us, you have the JDM parts and you plan to keep air conditioning, you'll have to trim the fan shroud to clear the A/C receiver/drier.

If you plan to use the stock intercooler, you'll need to enlarge the small hole in the inner fender below the stock air filter box. The intercooler inlet, outlet, and compressor bypass valve hoses need to pass through this hole. 1991 and later cars have the correct shape embossed in the panel already, otherwise refer to the front clip we keep telling you to buy.

The intercooler should bolt into place in the inner fender. Our car was missing one bolt hole, since it was built before the SR20DET was used in this chassis, but the remaining mounting bolts were enough.

The exhaust should bolt to the 240SX exhaust, (though you won't want to use it) as long as the downpipe came with the engine. In many cases the downpipe is missing, which gives you a good excuse to upgrade to a larger, 3-inch replacement. The missing downpipe problem is common enough that GReddy actually stocks 3-inch Silvia downpipes in the United States. We bolted the 3-inch GReddy pipe to our restrictive stock cat and exhaust just to get home. The GReddy downpipe came complete with the necessary gaskets and a mounting bracket to hold the pipe to the transmission, just like the stock one.

Hooking up the heater hoses will require two 5/8- to 3/4-inch adapters to mate the U.S. and Japanese hoses. A little finesse and a good supply of pre-bent heater hose fragments will go a long way here.

Neither the U.S. nor the Japanese throttle cable is long enough to follow the stock routing, but the Japanese cable will stretch straight across the engine compartment. We also used the Japanese gaspedal, since it has a stiffer return spring and mounts a little closer to the brake for easier heel/toe downshifts.

Engine Removal and Prep Work

Engine Removal and Prep Work

If your car has air conditioning, you'll want to have the system evacuated before removing the engine. If you plan on keeping the A/C, you must switch to the SR20 pump, and venting the A/C to the atmosphere is illegal. In a pinch, the twin-cam KA24DE's pump will bolt to the SR20 bracket, but only two or three bolts line up.

Next, remove the radiator, disconnect the power-steering lines from the pump, remove the entire engine wiring harness from the car, disconnect the fuel lines and unbolt the driveshaft. Slimy fluids come out when you do most of these things, so be prepared. Also remove the hood.

Now, yank the engine and put it on eBay.

If you bought an entire front clip, you'll have the pleasure of pulling the SR20 as well. Do yourself a favor and don't drop the new engine on its oil pan.

If you started with a 12-valve KA24E, the stock power steering pump will have been on the passenger's side. Since the SR20 power-steering pump is on the driver's side, none of the lines will reach. If you want to retain power steering, you'll need to search the junkyards for all the lines from a '91-'94 twin-cam 240SX. Your other option is to remove the stock lines, crank the steering back and forth a few times to pump out any excess fluid. Then cap off the power steering fittings. Voila. Manual steering.

Now is the time to clean the engine compartment and possibly even paint it. Check below the master cylinders for peeling paint and repair it now while you can get to it.

There are a few things you'll want to take care of on the SR20 before installation as well. Two of the studs on the bottom of our turbo outlet were missing. We replaced them with new studs for a VG30DE (Nissan part number 14064 7B000). Our engine also had an AIV valve, which is an emissions control device that lets air into the exhaust manifold at idle to keep the catalytic converter working. Later SR20s eliminated the need for this valve by simply leaning out at idle.

Jim Wolf Technology can reprogram the ECU to use the later idle control strategy, and since a JWT ECU is one of the first upgrades we have planned, we removed the AIV valve and capped off the fitting in the turbo outlet with Nissan part number 14052-21R00. The AIV valve has no effect on performance, so leaving it in place is harmless. If you don't care what comes out your tailpipe, removing it is also harmless.

We also removed the heatshield from the bottom of the turbo. This shield can contact the steering shaft under cornering loads, possibly locking the steering.

While you have the engine on the ground, this is a good time to consider replacing the clutch. Our engine only had 60,000 kilometers on it, so the stock clutch could be fine, but it doesn't take much imagination to guess how it ended up in a junkyard so early. When we removed the stock clutch, we found a severely abused three-puck racing clutch.

For a replacement, we used a 9-lb. chrome-moly TODA Racing flywheel. Even though it only fits the rear-drive SR20, AKH Trading had the flywheel in stock in the United States. The Silvia clutch happens to be interchangeable with any front-drive Maxima clutch, so we used a JWT street clutch designed for a Maxima. The JWT clutch uses an organic disc for smooth engagement and a stiffer pressure plate for increased torque capacity. Despite the stiffer pressure plate, the clutch is still light enough to be easily depressed by hand when we were bleeding the hydraulic system.

Right-hand and left-hand-drive cars have their heater core inlets in different locations, so some of the heater hoses need to be rearranged. Before installing the engine, the hoses on the back of the head need to be rearranged to point toward the passenger's side. See the photos for exactly how they need to be routed.

Picking the Engine

Picking the Engine

You'll need an engine and transmission for this swap. Ideally, you should also have a wiring harness, ECU and countless little brackets and doodads. If you're putting off the inevitable front-mount intercooler, you'll also want the stock side-mounted intercooler and piping. The easiest way to get all the parts you need is to buy a front clip, which includes the whole car from the A-pillar forward. We bought a 180SX front clip with 66,000 km on it for $1,500 from Venus Auto Parts in Sacramento, Calif. Venus sells the clips without bodywork. We also bought the Silvia fenders, hood, bumper and headlights for $500.

If you buy the engine separately, check the lower oil pan for dents. The SR20's oil pickup is mounted very close to the oil pan, and a dented pan can pinch off oil flow, usually resulting in immediate rod bearing failure. The pan only has to be very slightly dented for this to happen, so if you have any doubts, remove the lower pan (that's the stamped steel part, not the aluminum part) and check for score marks from the pickup. You can either hammer the pan back out, replace it (you have to get one from Japan) or upgrade to a GReddy or ARC high-volume pan. (The GReddy pan is baffled, the ARC is not.) With a stock capacity of only 3.5 quarts, the high-volume pan is a good idea.

There were several different versions of the SR20DET, which we've detailed in the table below. If you plan to upgrade the turbo, there's little advantage to the more powerful newer versions. A turbo upgrade on the earliest S13 engine will see it pumping out far more than the S15 engine in no time. If you simply plan to max out the stock turbo, the later turbos do have more potential.

Picking the Chassis

Picking the Chassis

The S13 240SX came as a fastback, coupe and convertible. The convertible is heavy, flexible and was only available with an automatic. If you're building a sports car, don't start here. Of the remaining body styles, the coupe is slightly lighter (about 50 lbs., depending on options) and stiffer, thanks to the added structure behind the rear seats.

The 240SX was available with ABS, a viscous limited-slip differential, and Super HICAS four-wheel steering. ABS from this era is relatively primitive, so we tend to avoid it. The HICAS system is probably another one to avoid. The rear-wheel steering is sometimes in phase and sometimes out of phase with the front wheels, and many people find it unpredictable and unsettling. There are several kits available to eliminate the system on cars that have it.

We've only experienced the system on Skylines, where it works quite well, so we can't comment on its effectiveness in the S13. A limited-slip differential is absolutely critical for what is about to be a very powerful car, but only cars with Super HICAS had the limited slip. If you can't locate a car with one, you can find one in a junkyard from a 240SX (all Canadian 240SXs had them) or a 300ZX, or there are aftermarket limited slips available. If you get a 240SX limited slip, be sure to get the driveshaft as well; it's about an inch shorter.1989 and 1990 models had a single-cam, 12-valve KA24E, while '91 and later cars used the twin-cam KA24DE. Since you're removing the engine anyway, this matters little, but the swap is a little easier starting with a twin-cam car. The power-steering lines from the earlier engine don't line up with the SR20's power-steering pump, and the tach signal from the SR20 won't drive the single-cam tach.

We found a relatively straight 1989 240SX coupe with 270,000 miles and a hole in the engine block for $800. It has no ABS, no HICAS, and, unfortunately, no LSD. It also has no sunroof, which is critical for tall drivers. Still weighed down with air conditioning, power windows and a fender full of Bondo, it tipped the scales at 2,710 lbs. before the conversion.