The timing belt is a very crucial part of the engine. It keeps everything lined up throughout the engine and it has to be perfect. Our 4G63 engines are interference engines. On an interference engine, the valves extend down into the path that the piston may travel into. If the timing belt fails, slips, or is installed incorrectly, there is a very good chance that the piston and valves will make contact. The result is snapped or bent intake and exhaust valves and/or worse.
There are a few things that can cause a timing belt to slip or fail. The timing belt itself can snap, which is very common. The timing belt AND ALL OF THE OTHER TIMING BELT COMPONENTS must be changed at least every 60,000 miles. Not doing so can result in timing belt failures.
List of things that commonly cause timing belt failures:
- Poor timing belt which ends up snapping.
- Tensioner pulley failure.
- Tensioner pulley not adjusted properly.
- Tensioner pulley bolt loosened. (use blue loctite on this bolt to prevent it from backing out)
- Auto hydraulic tensioner failure.
Many people live in fear of doing their own timing belt jobs, but replacing the timing belt is actually pretty simple. If you plan to build your own DSM, being able to time your 4G63 becomes a very useful skill.
There are three main timing marks that need to line up properly. (NOTE THE FOLLOWING INFORMATION IS FOR THE 2G 7 BOLT ENGINE. THE 1G 6 & 7 BOLT ENGINES ARE SLIGHTLY DIFFERENT)
Oil Pump Sprocket
Cam Gear Timing Marks
There is a timing mark on both the exhaust cam gear and the intake cam gear. Each mark has to line up together. On the exhaust cam gear, the timing mark is in the 3o’clock position. On the intake cam gear, the timing mark is at the 9o’clock position. These marks need to line up together.
There are also dowel pins on each cam gear, which are supposed to be on the 12c’clock position (straight up). If these are in the 6o’clock position (straight down), then the timing is 180 degrees off. The cam gears also have timing marks 180 degrees off from the correct timing marks. So, make sure your dowels are straight up.
Oil Pump Sprocket Timing Mark
The oil pump sprocket timing mark needs to be lined up if you are still using balance shafts. Not only does it need to be lined up, it needs to be in phase. This sprocket runs the oil pump gear but it also runs the rear balance shaft as well. Because of this, the balance shaft needs to be in the correct phase. Every three full turns is a complete phase. If the balance shaft is not in phase, it will generate a vibration.
There are a couple of ways to test this. The easiest way is to put the oil pump sprocket’s timing mark perfectly vertical. Then, let it go. If it falls counter-clockwise, it is in phase. If it goes clockwise, you need to rotate the sprocket 360 degrees and do the vertical test again.
The other way is by removing the balance shaft check bolt from the back of the block and inserting a screwdriver inside. If the timing mark is lined up AND the screwdriver can be inserted 2.4″ into the block, the balance shaft is in the correct phase. If the screwdriver can only be inserted 1″ or less, you must turn the oil pump sprocket one full turn and then check again until the screwdriver can be inserted 2.4″.
Crank Timing Mark
The crank timing mark is on the crank trigger plate and needs to line up with the appropriate mark on the front case. Please note that whenever removing the crank sprocket and trigger plate that you install the trigger plate exactly how you took it off. If you install the crank trigger plate backwards, the timing will be 180* off. Also note that every 3 turns at the crank is one full turn at the cam gears.
Buying a Timing Belt
There are many of different brands and types of timing belts available to us. The most trusted is an OEM timing belt (part #- MD326059). The OEM Evo IX timing belt (part #- 1145A038) can be used as a good replacement to our OEM timing belts. The Evo IX timing belts were made out of Kevlar and are said to be much stronger and durable. All 4G63 DSM and Mitsubishi Evo I-VIII share the same belt and same part number.
Gates Racing makes great quality timing belts as well. They make the regular OEM replacement timing belt or a stronger racing timing belt that is blue. I personally use the Gates Racing Blue timing belt.
HKS also makes great belts but are the most expensive. The HKS timing belts are purple.