How to Tell If You Have an Interference Engine?

You have two options to pick from when preferring the operational technology of a car with a petrol-powered combustion engine; they are either interference or non-interference. Now, the big question is how to tell if you have an interference engine or a non-interference engine.

To begin with, interference combustion engines are powerful, reliable, and durable; hence most modern vehicles are designed to run on interference engines.

Interference engine type comes with a couple of advantages that have made it a common choice for most people for some decades now. However, it has a disadvantage that only regular checks and maintenance can help you overcome.

Should you be worried because your car runs on an interference engine? Well, maybe not! The subsequent section provides a distinction between interference and non-interference engines.

Differences between Interference and Non-Interference Engines

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Differentiating between an interference engine and a non-interference engine is pretty easy if you understand their internal workings. If you are asking, “What is an interference engine?” Here’s what it means.

Interference engines are four-stroke vehicle engines with fully open valves, such that the valves move towards any area that the piston travels.

The engine is called an interference engine for a purpose; because the piston interferes with the completely open valves and occupies the same space. Also, there is no gap between the completely open valves and the piston on the top dead center of an interference engine.

Of course, there is a precise answer for those asking, “What is a non-interference engine?” A non-interference engine is the opposite of an interference engine. In this case, the piston doesn’t move into the space of the fully open valves due to the gap that exists between them.

A major challenge with an interference engine is the severe engine damage caused by a timing belt or chain breakage. This is not so with a non-interference engine. So, should you panic because of this? No.

The interference engine damage can be averted through constant inspection of the timing belt to identify marks that can lead to a timing belt breakage when you least expect it.

Also, besides the disadvantage identified above, interference engines come with a higher compression ratio with a proven ability to breathe better than non-interference engines. They are known for delivering improved performance and higher efficiency than non-interference engines.

How to tell if You have an Interference Engine

First and foremost, it is essential to note that most modern vehicles are fitted with interference engines. It is most likely that you drive a car with an interference engine as well. However, let’s find out how to tell whether your car has an interference engine.

Google and crosscheck your car’s engine model

There are no mysteries to finding out whether your vehicle runs on an interference engine. You can simply search the list of vehicles with interference engines on Google and crosscheck your vehicle’s engine model number with the one of the specific vehicle make and model that looks like yours.

For example, you can type “GM interference engine list” or “Toyota non-interference engine list” on Google and click on search to find out the various GM brands fitted with interference engine or Toyota brands that run on a non-interference engine. 

Have a chat with an expert auto mechanic.

Another easy way to find out if your car runs on an interference engine is to schedule a meeting with an expert auto mechanic in your neighborhood. If you don’t mind, you can do that this weekend.

Most auto mechanics are professionals, and as such, they know virtually all vehicles fitted with interference engines and those that run on non-interference engines.

So, your mechanic should be able to unveil whether your car runs on an interference engine or not, after a moment of inspection on the car, especially around the engine compartment.

Do not forget to ask the best way to maintain an interference engine to prevent it from faults or damages. It would be best to draft an outline of questions to ask your mechanic before the meeting so that you can be better enlightened about your car after the meeting.

what is an interference engine


What vehicles have interference engines?

If you are asking, “What cars have interference engines?” the list of cars includes the following; Chrysler 1.4L, Audi 1.8L 1.9L Interference, all Acura (except SLX Interference), GEO 1.0L Interference, GM, Saturn 1.0L Interference, 1.5L, etc.

Most Toyota models are freewheeling, and a number of them come with interference engines. Typical examples are; Toyota Sequoia, Toyota Land Cruiser (1998 – 2000), and Toyota Tundra.

If your vehicle make and model aren’t listed above, and you are wondering whether your vehicle has an interference engine, kindly go through the section that exposes how to identify vehicles with interference engines.

What makes an engine an interference engine?

 Interference engines are four-stroke vehicle engines whereby one or more of the valves around the fully open space reaches any area that the piston travels while the engine is running. So, the piston interferes with the open valve by occupying the same space.

No gap exists between the fully open valve and the piston on the top dead center (TDC) of an interference engine. On the contrary, a gap exists in the case of non-interference engines. Yes, this is a fundamental distinguishing factor between an interference engine and a non-interference engine.

What happens if a timing belt breaks on a non-interference engine?

When you experience a timing belt breakage in an interference engine, a few teeth will be skipped on the cam or gear. In that case, the crankshaft rotation and that of the camshaft will not synchronize properly.

The timing belt breakage will automatically result in the pistons striking the valves because they will continue to move and hit the valves in a fully open position. When this continues, it will damage the valves and most likely damage the vehicle’s engine as well.

As a result, a timing belt breakage in a non-interference engine will automatically stop the vehicle’s engine from running. It won’t lead to the piston hitting the valve as in the case of an interference engine.

The remedy, in this case, would be to re-time the vehicle’s engine and get a replacement for the broken timing belt. Once this is done, you can be sure that your vehicle’s engine will run flawlessly again.

What engines are non-interference engines?

Going back to defining engine type, non-interference engines are vehicle engines that have no room for the piston to interfere with the valves. The engine is completely a direct opposite of an interference engine whereby the piston enters the space created by the fully open valves. The non-interference engine list includes the following:

  • GM Non-Interference Engines: 2.0L Non-Interference, 1.4L Non-Interference, 1.6L (LeMans) Non-Interference, 1.6L SOHC (Nova) Non-Interference, 1.6L DOHC (Nova) Non-Interference, 2.3L Non-Interference, 3.4L Non-Interference, etc.
  • Toyota Non-Interference Engine: 1.5L (3E-E & 5E-FE) Non-Interference, 1.6L DOHC (4A-GE & 4A-GZE) Non-Interference, 4AF Non-Interference, 1.6L DOHC (4A-F & 4A-FE) Non-Interference, 4AFE, 1.8L 7AFE, 2.5L Non-Interference, etc.

Other vehicles with non-interference engines include; Honda 3.0L and 3.2, Acura SLX, Chrysler 1.7L Non-Interference, etc.

Is the 4age an interference engine?

The 4age is not an interference engine, except for those with huge cam. Toyota manufactured the Corolla Levin AE86 and Sprinter Trueno (1983) with 4age engines, making them the first set of vehicles to be fitted with that engine type.

If you drive a vehicle with a 4age engine, you may not have to face the challenge of a broken timing belt, which can most likely damage a vehicle’s engine. Since the 4age engine is a non-interference engine, it is not susceptible to such a costly problem.

Is a 3.7 dodge an interference engine?

Yes, a 3.7 dodge is an interference engine. However, it is pretty different from most interference engines that are susceptible to severe engine damage when their timing belt breaks.

In the case of the 3.7 dodge, there is zero probability of the timing belt going off time or breaking, thereby damaging the engine. However, this can only be possible when it is timed right at the initial stage. This is a serious condition to avoid a timing belt breakage.

Is a 4.7 V8 an interference engine?

A 4.7 V8 is not an interference engine; however, it is an excellent engine type. A 4.7 V8 is not threatened by the severe outcome of a broken timing belt because it is not an interference engine. One of the main challenges of a 4.7 V8 is that they don’t like being overheated at all.

The 4.7 V8 can last very long, provided the engine is kept running under good conditions with regular maintenance. Also, avoiding situations that could lead to the engine overheating will enable you to maximize this engine’s excellent performance, durability, and reliability.

Is a 2.4 Ecotec interference engine?

Yes, a 2.4 Ecotec is an interference engine, and as such, the traveling of the pistons and valves overlap. One common challenge here is that the pistons will have direct contact with the valves when the timing belt jumps or breaks.

The consequence of an interference engine’s timing belt breaking is the same for a 2.4 Ecotec interference engine. The direct contact between the pistons and the valves will most likely cause severe damage to the vehicle’s engine.

So, if you own a GM 2.4L Ecotec, always check the timing chain to know whether it’s in good shape. Inspect for any slack, marks, or scuffing that could easily lead to breakage, especially when it is least expected.

Is GM 3.6 an interference engine?

The GM 3.6 is not an interference engine; however, it seems to have almost the same effect when the timing belt breaks. The broken timing belt or chain can cause serious trouble for the engine if not rectified immediately.

Besides the trouble the engine faces from an occurrence of a broken timing belt, it is an incredible engine.

The GM 3.6L possesses some outstanding qualities, such as; high torque delivery over a wide rpm band, low emissions, excellent fuel economy, harshness and vibration control, and extreme durability with low maintenance.

Final Words

No doubt, a lot has been said about interference and non-interference engines in this article. So, you should know how to tell if you have an interference engine or not with the recommendations above.

As I said, it is most likely your car runs on an interference engine because it is common in most modern vehicles nowadays. If this is true, you must try by all means to prevent your car’s timing belt from breaking by checking it out often.

Besides that, if your car is fitted with an interference engine, that’s a great one right there. Go ahead and maximize the benefits of having such a powerful engine with top-notch delivery.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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