We're going to take a look at what most people consider the most critical component of a naturally aspirated engine: the camshaft. A camshaft can change an engine's character considerably; from torquey city cruiser to a high-revving, fire spitting drag queen.

In this particular case, we're installing a JG Engine Dyanamics #301x camshaft into a 1990 Civic Si owned by Gavin Miyasaki of Huntington Beach, California. This cam sports a 274§ intake duration with .370" lift, and exhaust duration of 260§ and .360" lift. While it seems that this is a rather hot grind for street use, we found that horsepower and torque production increased nearly across the board. The only other engine modifications were an HKS Super PowerFlo, DC Sports header, and HKS cat-back exhaust. The ECU, throttle body, and bottom end of the motor are stock.

On the stock cam, peak horsepower was 140@6000 RPM, and peak torque was found to be 114 ft-lbs@5100 RPM. After the JG 301x cam was installed, peak horsepower jumped to 156@6400 RPM, and peak torque settled at 122@5500 RPM. According to Honda, the bone-stock 1.6L mill churns out 108hp@6000rpm and 100 ft-lbs @ 5000 rpm. (Measured at the wheel.)

The Process

1. Remove the negative battery post, ground strap attached to the valve cover, the PCV connection, spark plug wires and spark plugs. You might find it helpful to tie up the clutch cable, to get it out of your way. Removing the spark plugs will help facilitate turning the engine over by hand.

2. Remove the valve cover and turn the engine by hand so that Cylinder One is at TDC. ONLY turn the engine counter clockwise! (Looking at the cam pulley from the drivers' side.) Remove the valve cover and loosen the timing belt tensioner; CAREFULLY slip the timing belt off the cam pulley. If your timing belt is due for replacement, now is the time to do it!

3. Unbolt the rocker arm assembly according to your service manual. There is a specific torqueing sequence to follow so that you don't warp the rocker mounting shafts. If you are in doubt, PLEASE email us at tech@overboost.com. (If the required information is urgent, don't forget to include your phone number!) Lift out the entire assembly; we found it helpful to leave the mounting bolts in the holes so the rockers don't slide off the mounting shafts.

4. Lift out the stock camshaft, and place it in a clean area along with the rocker assembly. Depending on where you bought your cam, the stocker may need to be returned in order to get your core charge refunded.

5. The cam and rocker assemblies.

6. The cylinder head sans camshaft and rockers. Note the oil bath that the cam resides in.

7. Coat the new cam with assembly lube, and place it into the cylinder head. The Honda distributor only allows you to install the cam one of two ways; make sure the word "UP" on the cam pulley is indeed pointed up!

8. Place the rocker assembly back on the head and camshaft. Torque the bolts to 16 ft-lbs using the torqueing pattern in the manual.

9. Reinstall the timing belt and tighten to factory spec. Adjust the valves and turn the engine over two times by hand, making sure there is no valve-to-piston contact. The valves will be WAY out of spec; the JG cam is a factory regrind, which means you'll be adjusting the valves into the cam lobe, which provides the additional valve lift. When you are finished, put Piston One at TDC and make sure the reference mark on the cam pulley lines up with the reference mark on the valve cover. (There are two marks for Honda 1.5L engines.)

10. Reinstall the valve cover, negative battery post, ground strap, PCV, spark plugs and spark plug wires.

11. When you are finished, start the engine. You may have to re-set the base timing to get the engine started. The idle will erratic; you can correct this by adjusting your idle speed, disconnecting/ reconnecting the idle air control and finally resetting the ECU by removing its' fuse for at least 10 seconds.