NA Timing Belt Steps

Original Author: Phil Barnett (prb) - 2013

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Do not bother marking your existing belt position. If the belt was on wrong to start with, you will simply retain that wrongness. If your Timing Belt broke or slipped, you'll need to know how to index the Timing Belt from scratch anyway. If you removed the old belt and the pressure from the valve springs caused a cam or both cams to rotate, it will make it difficult to return the markings to the expected orientation.

All the marks it takes to properly install the Timing Belt are built into the engine. The entire following process should take about 10 minutes once you get through it the first time.

When I say left and right, you are facing the engine from the front of the car.

The steps in this guide assume you have removed the clean air crossover tube, the valve cover (and maybe the coil packs are loose), the accessory belts and the front covers. If you are just insuring that the timing belt is set right, you can leave the bottom cover on and shine a flashlight down to see the half moon alignment. This also allows you to leave the harmonic balancer in place.

Before you start, remove the timing belt idler and spring assembly on your left. Install the one on the right and torque it down. This is all easier to do if you don't have spark plugs in the engine and the transmission is in neutral. (or the drive tires are off the ground with the e-brake off)

Prior to this process, it will be helpful if you have found the small index marks (two on each cam sprocket) and filled them in with some white paint. Of course, the paint won't stick to a greasy part, so clean them first.

I'm using a Gates TCK179 Timing Belt Component Kit, which is an exact match for the factory timing belt components.

  1. Turn the crankshaft clockwise until the half moon cut out aligns with the 12 o'clock arrow.
  2. Remove the cam sprockets from the front of the cams and rotate each cam clockwise until the dowel pin that indexes the cam sprocket is at 12 o'clock.
  3. Put the cam sprockets on with the I up on the Intake cam and the E up on the Exhaust cam. Put a wrench on the cam flats and torque each cam sprocket bolt.
  4. Look at the cams. The front lobe (cyl 1) on each cam should be pointing towards the fender on that side of the engine. If they are, go on. If not, go back to step 2.
  5. Turn the exhaust cam clockwise until it starts pushing down on the cylinder 1 exhaust valve and then let it relax back a little bit counter clockwise.
  6. Put the belt on the crank and shim underneath it with cardboard so it won't slip.
  7. Wrap the belt counter clockwise from the crank to the exhaust cam sprocket but not the intake sprocket. The belt goes to the left of the right idler bearing. This should make the belt tight on the right side. If it's not tight, rotate the exhaust cam slightly clockwise when slipping the belt on. I tie the belt to the exhaust sprocket with a tie wrap at this point. The tension of the valve spring on the #1 exhaust cam should hold the belt tight on the right.
  8. Put a wrench on the flats on the intake cam and turn it counter clockwise until you can slip the belt on. Count the number of teeth between the two marks on the cam sprockets. It should be 19. If it is 18, slip the belt off and rotate the intake cam one more tooth counter clockwise.
  9. Tie the timing belt to the intake sprocket with a tie wrap. Insure 19 teeth between the marks.
  10. Slip the left idler and spring assembly under the belt and attach it but don't tighten it. You might require help for this next step... With a wrench on the flats, turn the intake cam slightly counter clockwise to take the slack out of the top of the belt and tighten the left idler against the belt and snug the bolt (not torqued yet). Remove the tie wraps you used to tie the belt to the cam sprockets. Remove the cardboard shim.
  11. Turn the crank 1 and 5/6 turns clockwise to align the half moon cut out with the arrow at 10 o'clock on the block. Make Sure there is no slack in the driver side or top run of the timing belt. You can slightly turn the intake cam counterclockwise with a wrench on the cam hex flats till the crank just starts to turn counterclockwise. All slack is now in the passenger side run of the timing belt, for the spring loaded adjuster bearing to remove.
  12. Tension the belt following these instructions: http://wiki.miata.net/tiki-index.php?page=NA%20Belt%20Tension
  13. Torque the left idler bearing.

Turn the crank clockwise to TDC (half moon in 12 o'clock notch) and check for cam sprocket alignment and tooth count. If it's not right or the cam sprockets aren't symmetrical, go back to step 5.


http://www.rivercityroad.com/garage/pics/biggear1.jpg (The half moon cutout is aligned with the arrow in the casting)



Turn the crank clockwise 1 and 5/6 turn and check for belt tension a second time.

This a slightly modified method that is well described here:


ItemSAE (ft lbs default)Newton/Meters
Cam Sprocket Bolt37-4450-60
Timing Belt Idler Pulley28-3838-51

Added by Coaster, June 2014

Here is a method to verify your installation should you be unsure: In addition to the two marks on the cam gears, add a third mark on the crankshaft cog gear tooth directly opposite the keyway and gear timing mark. (http://forum.miata.net/vb/picture.php?albumid=3085&pictureid=14332). If you have 19 teeth between the marked intake and exhaust gear teeth and 63 teeth between the exhaust cam mark and the third mark at the bottom of the crank cog, you are correctly set up. You can pre-mark the new belt with a white paint marker to simplify installation if desired.