Engine Tuning: Droppin' ZEX-tasy

If computing camshaft specifications wasn't hard enough, Honda had to toss VTEC cam profiles into the mix. This has made cam designers re-think all that they have learned in order to set up added horsepower in VTEC trim.

ZEX is one such company that has mastered the SOHC VTEC grind. Overshadowed by the mighty DOHC engine, the single-over-head model has always been thought of as an inferior powerplant. ZEX has brought new meaning to the SOHC engine with their new billet camshaft. The company claims that the cam is superior to all other drop-in cams so we decided to give the cam the 2NR torture test.

With our test vehicle strapped to the dyno, we first did a baseline test to see what our car puts out with only a few bolt-ons installed. Considering that our car was equipped with the basic components (filter, exhaust and header), we thought our figures were wrong due to the high peak output of 123 hp and 103 lb-ft of torque. We ran a second dyno to ensure our figure was correct and sure enough, we hit the same numbers.

After the cam was installed and broken in, the car was strapped back to the dyno to finish our drop-in testing. Although the cam was fitted with a sprocket, testing of the cam was done with the sprocket at zero. This was to ensure that the cam made power by itself. The ZEX cam provided excellent power throughout the power band with a peak of 7 hp and 2 lb-ft of torque.

This was power, but what we found most valuable was the gain in the mid-range where we discovered as much as 11 hp and 9 lb-ft of torque. The cam makes good effective power for the after shift.

The ZEX camshaft was the most effective SOHC cam we have tested and made for a quick install. The power output from the cam is well worth its dollar figure and, with the addition of a sprocket, there is always room for additional powerband tweaking. The greatest part about the unit is that there is no core deposit, so you always have the option to go back to the stock cam. Then again, once you've had ZEX, you'll never look at the stock camshaft in the same way! Be sure to practice safe ZEX.

		The 14mm belt must be loosened...        read full caption The 14mm belt must be loosened to slip the belt off the sprocket.
Removing the rocker arm assembly...        read full caption Removing the rocker arm assembly requires loosening all the 12mm and 10mm bolts holding the unit. When removing the assembly be sure not to pull the bolts out of the unit for the fact that they line up the rocher shafts with the cam journals.	Remove the cam.	Place the cam seal onto the...        read full caption Place the cam seal onto the ZEX cam and grease the lobes with engine assembly lube.
	To ensure that there is no...        read full caption To ensure that there is no oil leak place a light film of silicone on the outside surface of the cam seal.
Tighten the rocker assembly...        read full caption Tighten the rocker assembly bolts back onto the head, to the factory-mandated torque ratings. Be sure that the cam is on its top dead center mark.	Refer to the factory manual...        read full caption Refer to the factory manual to ensure the valve adjustment is done in the proper manner.	Reinstall the valve cover...        read full caption Reinstall the valve cover with anything else that was removed to its proper location.