Through the years, Nissan's SR20DE engine proved a willing participant when it comes to building horsepower. The normally aspirated SR20DE 2.0-liter four boasts 140 hp and 132 lb-ft of torque in stock trim, which is more than enough to properly propel any of the NX 2000s, SE-R Sentras, 200SXs and Infiniti G20s it appears in.
Stock trim is fine, but here in the Dyno Cell, it's all about power. The SR20 has a number of pluses. It's fairly light, thanks to its aluminum block, aluminum head design. The block's closed deck configuration means there is no need for sleeves or block guards. Everything in the SR20 is stout (especially the rods) because the powerplant is turbocharged in Japan where the engine powers the Silvia sport coupe.
Beyond the internals, the SR20 runs a very stout valvetrain in stock trim. The head features a mechanical lifter assembly that incorporates one rocker arm per two valves which means one cam lobe per two valves. Since the rocker arms are floating and the lifters are hydraulic, no valve adjustments are needed for the Tomei units. Rather than using a timing belt, Nissan has paired the timing chain with a hydraulic chain tensioner. This system tends to out-last belt systems, but can sometimes complicate matters during installation of cams or making adjustments to engines equipped with cam sprockets. In this cam story, we have used a different installation method than that found in the factory service manual.
With the Sentra strapped to...
With the Sentra strapped to the Dynamic Autosports dyno, we laid a foundation of 133 hp and 125.0 lb-ft of torque. With the Tomei cams installed, the SR20DE engine pumped out 141.9 hp and 127.0 lb-ft of torque. A peak of 8.9 was realized, but 10 to 15 hp was found in the high-rpm range from 6000 rpm to redline.
Remove the valve cover by...
Remove the valve cover by loosening the 10mm bolts that fasten the cover to the head.
The Tomei cams are considered direct replacements. They utilize the same size base circles as the factory units, which helps in eliminating harsh rocker arm angles. The cam sprocket dowel pin for the intake sprocket is within factory spec but the exhaust sprocket dowel comes in a much longer length. This is done to accommodate rear-drive SR20 engines that run cam sensors on the sprocket. If these Tomei units are to be installed in front-drive vehicles, either the dowel needs to be cut to the proper size or the sprocket bolt washer needs to be grooved to accept the protruding dowel.
Our test vehicle is one that has been through grueling tests in the past. From being a turbocharged guinea pig with a full-blown, race-ready engine to an all-motor SR20 test bench, Project SER-ious Sentra has been tortured tested on many a Dynojet dyno.
Currently, the engine is stock with a few basic bolt-on upgrades. Although the engine is tired, the baseline figures show that even an SR20 with miles can produce good power. A baseline figure of 133.0 ponies were present and 125 lb-ft of torque was still plenty to motivate the Sentra. To futher view the process of installing SR20 cams and resulting power, follow along as we show you the easiest and least time consuming way to make bolt-on power. Let the boogie begin.
It is necessary to loosen,...
It is necessary to loosen, but not remove, the 24mm bolts that attach the sprockets to the cams before cranking the engine to its TDC (top dead center) mark. Placing an adjustable open-end wrench on one of the cam's lobe will keep the cam from moving while you loosen the bolts. To ensure the timing does not fall off its original mark, use two wire ties to lock the chain to each sprocket.
Setting the engine at TDC...
Setting the engine at TDC must be done by cranking the engine clockwise, and lining up the crank pulley's TDC mark on the timing chain cover's TDC pointer. The TDC marker on the pulley is on the far left.
The factory manual says to...
The factory manual says to remove the tensioner, compress and lock it, but we decided to make a tensioner tool to keep the chain tensioner from expanding. Although making the tool takes about 20 to 30 minutes with the proper wood making tools, this little device saves about 2 to 3 hours from the normal tensioner process. Trust us: Save yourself the headache from the normal long and grueling task of removing the necessary parts just to get to the tensioner. (check out www.turbmagazine.com for details on building this handy tool yourself)
Place the chain block between...
Place the chain block between the two sprockets and firmly press the unit so it locks the intake side of the chain.
With the block in place, finish...
With the block in place, finish removing the sprocket bolts and upper chain guide and pull the sprockets away from the cams.
Before removing the distributor,...
Before removing the distributor, be sure to mark the cam journal and distributor with a punch or white correction fluid. To ensure distributor timing is correct, remove the distributor cap and mark the rotor's position. Since the engine is at TDC, the rotor should be pointing to the 5 o' clock position. Once this process is complete, remove the distributor.
With the distributor removed,...
With the distributor removed, the cam journals can now be loosened. Do not remove the journals until all the bolts have been loosened to free the tension on the cams. Once the tension from the cams is released, you can remove the journals and the camshafts.
Place all the journals in...
Place all the journals in their proper order so when they are reinstalled, they're set back in the proper order.
Follow the factory service...
Follow the factory service manual for torque sequence. The 10mm bolt will be torqued to a max of 9 lb-ft of torque while the two 12mm bolts will be tightened to 19 lb-ft of torque.
Lube the Tomei camshafts using...
Lube the Tomei camshafts using moly lube to ensure proper break-in. Place the new camshafts in the same position as the old units, but be sure the lash pads and rocker arms are in good condition and set in their proper place. The exhaust cam is distinguished by its distributor slot on the opposite end of the cam sprocket side and must be placed towards the driver side of the vehicle. With the cams in place, set the intake sprocket dowel pin at the 10 o'clock position and the exhaust dowel pin at 12 o'clock. This ensures the cams are set at TDC.
Once the cams are torqued...
Once the cams are torqued to spec, the distributor can be loaded into the exhaust cam journal. Be sure that the marks on the distributor are lined up. This is to ensure proper distributor timing is maintained.
Place all the cam journals...
Place all the cam journals back in their original spot, with the arrows pointing toward the sprockets.
If they were aligned properly,...
If they were aligned properly, the cam sprocket should be able to slip onto the cams with very little or no movement of the camshafts. Once the sprockets are secured in the head, use an adjustable open-end wrench to hold the cams in place while tightening the sprocket bolts.
With the sprockets fastened...
With the sprockets fastened to 116 lb-ft of torque, the upper chain guard can be bolted and the tensioner tool can be removed.
Let the rollers spin.