Chevy 350 Common Problems - What to Expect in Use?

Chevy 350 Small Black Engine is a legendary unit that was in production for almost half a century and changed many generations and modifications. We should say that this is one of the most massively produced GM engines that was used in both passenger cars and commercial vehicles. And the commercial use makes us have a thorough look at this powerplant.

Exactly, we'll be looking at one of the latest modifications of the 350 engine - L31. But actually, nearly all problems of this model are common with all other 350 engines. Our attention is on the L31 version because it was mainly made for commercial use. Today, we'll tell you about the common problems with the Chevy 350 engine and will show some weak points in the machine.

Here's what exactly we'll tell you about:

• What's the Chevy 350 engine like and what should you know about it?
• How long will these engines go in commercial use?
• What are the common problems with 350 engines?
• How to make sure GM 350 engines will live longer?

Let's get started!

Key facts about the 350 engine (L31 series)

So, the L31 small block engine was first introduced in 1996. It was also named Vortec 5700 which is probably the more common name for this powerplant. The engine was totally based on the technologies of other 350-series engines and basically had just some minor changes to fit into commercial vehicles.

It was used in Chevrolet full-size trucks like the C/K, Chevy Express Van, G-Series vans, and also Isuzu box trucks of numerous models. Also, the engine was used in SUVs like Tahoe and Suburban. One of the exotic applications was the Oscar Mayer Wienermobile - the vehicle in the shape of a hot dog to promote Oscar Mayer products.

Here are some key things you should know about the engine:

• it's the 5.7-liter V8 gasoline engine with 255 to 350 horsepower depending on the version and with up to 350 lb-ft of torque;
• the engine was the last unit of the first-generation Small Block engines by GM;
• the L31 head is basically the same as in all small-block engines of the first generation, so the heads are compatible;
• the 350 engine is actually still in production as the crate engine (and it's exactly the L31 version) for marine use and also as a replacement engine or the unit for project cars;
• the 350 engine is extremely popular for RVs, project vehicles, exclusively built trucks, etc.;
• this is a very reliable and pretty simple engine with not a lot of common issues to care about;
• some engines are fitted with carbs while some have TBI - throttle-body injectors;
• the gas mileage is not really good, commercial vehicles will show an average of 10-12 MPG.

We should say that some experts named this engine the best powerplant of the 20th century. And a lot of facts prove that. The engine is used in the marine industry where manufacturers are very careful about choosing a good engine. The powerplant is still in production and is popular as a crate engine. The unit is powerful, quiet, and offers great performance.

Also, it's reliable and doesn't need a lot of maintenance or repairs. One more important thing - you can find relatively cheap and high-quality parts, both new and used. So, owning this engine is not expensive. And it's really important for any commercial user. Of course, we shouldn't bother about gas mileage and ecology much when we are talking about this engine, but still...

How many miles will the 350 engine go?

It's not easy to estimate the lifespan of the Chevy 350 engine, but we'll try. The average longevity should be about 250,000 miles up until you start getting the first problems. But this is not the whole life cycle of the engine. After the rebuild, the engine can go at least another 150,000 miles before replacement.

We've also seen Isuzu trucks with over 600,000 miles on them and all those miles with the same 350 engine. It means if you provide it with a little TLC, it will pay you back with enormous durability and a wonderful cost of use.

Maybe, the only problem is gas mileage because it makes the engine a little more expensive than modern powerplants. But if you compare durability and repair costs, any modern engine will be able to compete with the 350 engine. We are talking about the L31 version, but actually, this is true for all 350 small block engines.

So, longevity is pretty good, but what about some common problems?

Issues and problems with the GM 350 engine

The GM 350 engine is not without its share of problems. But we should say that most issues happen with this engine just because it's now mainly old and with a lot of miles on it. If you get the new 350 engine, you will be able to enjoy problem-free use for some years.

Still, some issues need to be taken into account.

1. Bad starting

Unfortunately, the fuel supply system and also the ignition system are not very modern and efficient. It means that you will need to maintain them all the time and will still sometimes experience a hard starting. At times, you will have to try hard to start the engine.

Common reasons for this are a bad fuel pump, a clogged injector (for TBI versions), bad spark plugs, etc. But sometimes the problems can be more unexpected and will need a professional diagnosis.

2. All sorts of knocking sounds

In most cases, valves are knocking because of poor lubrication. Just check the level and the quality of the oil in the engine. Also, the oil pump may fail. If this happens, you may kill the engine pretty quickly. So, if you hear a knocking sound when you drive, the best decision is to stop the engine immediately.

A knocking 350 engine is common when it gets over 200,000 miles. Before that, any knock should be treated with a certain amount of attention.

3. Overheating problems

When the engine overheats, it may easily kill one or both heads, so the repair will certainly not be cheap. So, better keep an eye on coolant quality, water pump condition, timing system condition, etc. If the coolant level falls below the minimum, the engine starts overheating and this will cause some issues.

Even a slightly overheated 350 engine will have some problems. For example, one of the head gaskets may go bad and start leaking. After some time, this may lead to even more problems.

4. Leaks all over the place

This engine was made for tough work, not for convenient use, for sure. So, you will need to always pay attention to leaks. Once some liquid leaks, find the reason for the problem and replace a certain hose or connection. Otherwise, after 50-60 thousand miles your engine will be leaking from several spots and with several types of liquids.

Leaks are dangerous. If you don't pay attention to leaks, the oil level may drop or some coolant may leak away from the system. This will lead to poor lubrication or bad cooling which in turn will cause huge engine problems.

5. Sensor problems

Although this engine is not the most progressive in terms of electronics, it has some sensors like oil pressure or coolant temperature sensors. They may fail and you will not even notice it because there is no clever ECU that will send you the check engine light on the dash.

For example, a failed oil pressure sensor will only have one symptom: the oil pressure light will not go on the dash when you turn on the ignition. But if you don't notice this, the oil pressure problem will never be indicated on the dash and this may lead to issues.

What to do to prolong the life of the 350 engine?

It's really important to pay attention to the condition of the engine. If it asks for help by leaking, overheating, or not starting properly, it's too late to think about TLC.

You should remember these simple steps:

• keep up with oil change intervals and change filters even more often than needed;
• avoid using bad fuel (contaminated or with low octane number);
• stop the engine whenever you hear knocking sounds;
• don't rev up the engine too much;
• always remember about payload and towing limitations.

So, regular maintenance and understanding the limitations are important factors. Also, if your 350 small black engine asks for repair, never keep driving it. This may kill it right away.

Final words

We know that the 350 L31 engine is not the most efficient powerplant you may dream of. But it obviously has a lot of advantages such as quality, durability, cheap maintenance and repair, and simple construction. If these are the factors you are looking for in an engine, the 350 will be a good unit to buy.

But if you are looking to buy a used vehicle powered by this engine, be careful. After gaining over 200K miles, these units can really be problematic.