Installing Tomei Pon Cams (256 Degrees) Stage 1 on S13 SR20DET

This guide can be used to replace any drop-in replacement cams. We specfically chose the Tomei Pon Cams Stage 1 cam set since it offers such a high lift without having to replace other valvetrain components. They are a direct drop in replacement while at the same provide similar performance to higher lift and longer duration cams that require new valvetrain components.

Before getting started, you should gather all the tools you need and all the replacement parts & gaskets. You will also need a torque wrench to properly torque down the cam tower bolts. You should also replace the valve cover gasket and the spark plug well gaskets.

First, remove anything that may get in the way of the valve cover gasket. In the picture below, we had to remove the strut bar, the throttle cable, the brake booster hose, the oil breather hoses, and part of the wiring harness that is bolted onto the valve cover. Remove the valve cover and the timing chain guide.

Fig. 1 – Engine bay before work begins

In order to loosen the sprocket bolts, you can leave the transmission in 5th gear to lock up the engine. Using an extension (or breaker bar), loosen the two sprocket bolts as shown in the image below. Do not remove the bolts at this point – just loosen it. Put the transmission back into neutral so you can manually turn the crank in the next step.

Fig. 2 – Loosening cam sprocket bolts

This next step is very important. Using a ratchet on the crank pulley, hand crank the engine until the #1 piston is at TDC. This can be verified by looking at the crank pulley and the cam sprocket position. The crank pulley timing marks should be at the 2nd to the left mark while the notches on the exhaust cam sprocket is pointing perpendicular to the surface of the cylinder head, or at about the 12 o’clock position. The intake cam sprocket notch should be at about 10 o’clock.

Fig. 2b – Verifying TDC on compression stroke

When the engine is in position, put the transmission back into 5th gear to prevent accidental cranking of the engine while replacing the cams. You will need to remove the crank angle sensor.

Fig. 3 – Removing CAS

After the crank angle sensor is removed, remove the components on the exhaust camshaft side: you need to remove the cam towers, cam oil squirters, and the rocker arm stoppers (if you have it installed). All this comes out at once since they are all part of the same assembly.

Fig. 4 – Removing valvetrain components

Once those are out, remove the timing chain tensione.  Next, remove the cam sprocket bolts that you loosened earlier. With the help of another person, carefully pull the intake cam sprocket away from the cam while keeping tension on the chain so that it does not jump or skip.

Fig. 5 – Installing the exhaust cam

Mark the intake cam sprocket and chain’s position. Carefully pull the exhaust cam sprocket away from the cam while keeping it tensioned with your hands. Once the sprocket is seperated from the cam, you can replace the cam shaft with the Tomei Poncam. Rotate the cam until the notch in the front of the cam is oriented in the same direction as the old cam. If done correctly, the sprocket should fit right back on without any issues. Re-install the sprocket bolt and hand screw – do not torque it just yet.  Re-install the cam towers for the new cam.  Again, do not torque it down just yet.

Do the same for the intake side – remove the towers, squirter, and rocker arm stoppers (if you have it). Remove and replace the cam.  Have someone keep the timing chain tensioned so it just not skip any links/teeths. Carefully remove the intake sprocket from the chain while keeping it tensioned.

Fig. 6 – Installing the intake cam

Fig. 7 – Guiding the chain back on

Make sure the timing chain is sitting on the chain guide.  Re-install the sprocket on the cam.  It should almost fit right in.  If not, you may have to rotate the cam a few degrees.  Warning – do not rotate the cam degrees from the TDC position as damage to your valves/pistons may occur!

After the sprockets and sprocket bolts are on and hand tightened, you need to verify the position of the cams with the crank.  Make sure the crank is still at TDC.  The cam sprocket notch should now point at about 10 o’clock and 12 o’clock for the intake and exhaust with respect to the surface of the head.


Fig. 8 – Re-installing intake sprocket with some help


Here’s how the new cams look installed.  Push the tensioner back in and use the retainer clip to hold the tensioner in place.  Reinstall the tensioner.  Remove the retainer clip to tension the timing chain.  Hand crank the engine SLOWLY to allow the tensioner to fully tension the timing chain.

Fig. 9 – Here’s how it looks like after new cams are in

Verify that the engine is still at TDC (check the crank pulley to make sure it’s 2nd to left mark). Torque the cam towers, oil squirters, cam sprocket bolts, and rocker arm stoppers if you have them. Remember not to over tighten the cam tower bolts – the torque specs for those are really low. We torqued them to about 7 ft/lbs. Align the crank angle sensor and re-install it. For details on this step, visit our CAS guide.

Fig. 10 – 10 chain links from intake dot to exhaust dot

Valvetrain after everything’s re-installed. Notice the number of chain links from the intake sprocket punch mark to the exhaust mark. There are 10 links in between. Also verify that the dowel notch on the sprocket is pointing at about 10 o’clock and 12 o’clock for the intake and exhaust side, respectively. The cam and sprockets should be in the exact same position as shown in Fig. 2b. If there isn’t exactly 10 links or if the position is off, you will need to re-adjust the sprockets and cams to get it perfect. Do not proceed to the next step unless you are sure the cams are lined up correctly.

Pour some fresh oil over the newly installed cams. Put the transmission in neutral. Using a ratchet, hand crank the engine carefully to make sure the cams are installed correctly. If you feel any resistance (ie, the engine won’t crank), STOP and double check everything again. Once you are able to rotate the engine a few times, you can re-install everything.

Fig. 11 – All back together.

Now, for the good stuff (the results).

Because the vehicle is using MAP sensor, we weren’t able to take full advantage of the new cams without a minor retune. Using our old tune at the track along with our butt dyno, we noticed that the car pulls much harder from 3,000 RPM all the way up to redline. There was some loss in turbo response and power below that, but the gains made after was much more worth it. The car pulls and pulls up until redline whereas before it would bottom out after about 5,500 RPM. With tuning, the engine should be even more responsive with more mid and high range power. Stay tuned for some dyno charts!

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