Which SUBARU engines are interference? What SUBARU engines are non-interference?

Here is a table listing SUBARU engines, models, and years and which SUBARU engines are interference and which are non-interference.

This table refers to USDM (United States Domestic Market) SUBARU's. 

The SUBARU engine interference/non-interference chart above is available for download as an Excel 2007 spreadsheet here: SUBARU-engines-interference.xlsx

If the table/chart of SUBARU interference and SUBARU non-interference engines does not display properly in your browser, you can view the SUBARU interference/non-inteference engines list it as an image here.

This table aims to be as accurate as possible, but there are no guarantees.  Especially around model change years - sometimes in model change years early models of that year get some of the previous year's parts.

The SUBARU H6 6-cylinder 3.0L EZ30 engine is shown in the list above.  It has a timing chain with no set replacement interval; it is intended to last the lifetime of the engine.

Every SUBARU owner should know if their SUBARU's engines are interference or non-interference.  If the timing belt or timing chain breaks or jumps timing, it can cause bent valves and possibly dinged pistons in the engine, thus resulting in expensive repairs.

Fortunately you can get timing belt kits for Subaru vehicles at a reasonable price:

• Subaru timing belt kits on eBay
• Subaru timing belt kits on Amazon
• Both of the links above will let you enter your Subaru model and year to filter the timing belt kits to those that are for your specific vehicle.
• The Gates brand kits have a good reputation.
• It is usually best to replace all the idlers. The geared or toothed idler is often the one that will fail. Some of the original Subaru idlers had single row bearings in the idler pulleys. These did not last as long as the double row bearing pulleys. So some kits will use double row bearing pulleys for all the idlers.
• Replacing the water pump is often a good idea as well. Especially when the timing belt replacement interval is 100,000 or more miles. Will the water pump last another 100,000 miles? Maybe or maybe not. Considering that most of the labor is already done by getting the timing belt cover and belt removed, it makes sense to replace the water pump and thermostat at this time as well.

Why did SUBARU engines switch to interference from non-interference?

The valve to piston interference design allows for a higher compression ratio, which generally gives better fuel efficiency. Then the engine can be run very close to where it knocks, relying on the knock sensor signal to the ECU to retard the spark enough to stay out of knock.

The intake valve to exhaust valve interference design can occur on the DOHC (double overhead cam) engines. If the timing belt or chain slips or breaks, it can let both of the intake and exhaust valves try to be open at the same time, which means they could hit each other. Often times they do not though. It is more common if the timing belt breaks to have one or more bent valves from the piston hitting them.

But sometimes you can get lucky and not have any damage. So often people will put on a new timing belt and then do a compression test. If compression is exceptionally low in any cylinder, it may mean a valve is bent. If so it requires removing the cylinder head to replace the valve.

Another test some people do is, after putting on a new belt, if compression is low in a cylinder, mechanically block the engine from turning, and apply compressed air in the spark plug hole of the cylinder with the camshaft in a position where both the intake and exhaust valves on that cylinder should be closed. If there is a bent valve, the air can be heard blowing out either the intake or the exhaust, depending on which valve is bent.

If you have a question or comment, or would like a specific engine added to the list, please post below, or visit the SUBARU forum.