Ford 351 Windsor Engine Problems: 5 Most Common Problems

Ford built the 351 Windsor, a 5.8-liter small-block V8 engine, between 1968 and 1997. It is still in use today. It’s been around for a long time and is one of Ford’s most popular models. Informally known as the Windsor V8 engine family, the 351W comes from the Windsor, Ohio plant and is powered by a 5.0-liter V8 engine. From 1961 to 2002, Windsor small-block V8 engines were built with 90-degree OHV valve-in-head technology.

The 351 Windsor is the Windsor family’s largest V8 at 351 cubic inches (5.8 liters). The 351W has undergone numerous revisions and upgrades in the course of its nearly 30-year existence. Many changes have occurred over time, but these are some of the most significant:

  • It was changed in 1975, so the 1969-1974 blocks are much more durable and therefore more sought after.
  • In 1971, the height of the deck was raised to reduce the compression ratio.
  • In 1984, the one-piece rear main seal was introduced.
  • In 1994, the use of MAF took the place of speed density.
  • In 1994, lifters were introduced.
  • In 1988, the fuel injection system took the place of the carburetor.

Ford cars that use the 351 Windsor

  • 1968-1974 Galaxie
  • 1968-1970 Mustang
  • 1969-1970 Mercury Cougar
  • 1969-1991 Country Squire
  • 1969-1970 Fairlane
  • 1970-1976 Torino
  • 1974-1976 Ford Elite
  • 1975-1996 E-Series Vans
  • 1977-1982 LTD / LTD II
  • 1977-1979 Thunderbird
  • 1979-1996 Ford Bronco
  • 1979-1991 Crown Vic
  • 1987-1997 Ford F150/F250/F350
  • 1977-1979 Mercury Cougar Station Wagon
  • 1978 & 1986-1991 Mercury Colony Park
  • 1978-1982 Mercury Marquis
  • 1986-1991 Mercury Grand Marquis
  • 1980 Continental Mark VI

351 Windsor vs. 351 Cleveland

Ford built the 351 Cleveland, a 5.8-liter, 351-cubic-inch V8 that went on sale in 1969 and was produced until 1982. Cleveland, Ohio, served as the manufacturing center for the company, hence the Cleveland moniker. The 351 Windsor and 351 Cleveland are both 5.8L V8s, but they come from different engine families. The 351C, also known as the 351W or 351C, was a Ford “335” engine.

Ford developed the 351 Cleveland after realizing that demand for the 351 Windsor was outstripping the plant’s ability to produce it. It was for this reason that the 351s began to be produced at the Cleveland plant too.

Ford, on the other hand, chose to improve the performance of the Cleveland-built 351 engines by fitting them with a new cylinder head design. Both the 351W and the canted exhaust and intake valves and large ports of the new head designs were constructed.

The 351 Cleveland engine had a slew of different engine codes to further complicate matters. In the 1970s and ’70s, Ford made performance-oriented 351C variants known as the H, M, R, and Q. These were produced from 1970 to 1974.

A 351 Clevor is commonly made by swapping the heads of a 351 Cleveland with those of a 351 Windsor. It was well-known that the Windsor blocks were more durable, but the Cleveland heads had more flow and, as a result, more power.

Ford 351 Windsor Common Engine Problems

  • Timing cover coolant leaks
  • Cracked exhaust manifolds
  • Rear main seal oil leaks and gasket leaks
  • Broken intake manifold bolts
  • Weaker blocks (1975+)

It’s important to note that a lot of these issues stem from the fact that these engines are getting older. The engines’ blocks, internals, and heads, among other components, are incredibly durable and virtually indestructible.

1. 351W Timing Cover Coolant Leaks

The 351 Windsor’s timing chain and sprockets are shielded from dirt, mud, and grime by a cover. A gasket secures the timing cover to the block with bolts on the front.

The timing cover gasket degrades over time, as is common with gaskets, and eventually leaks. Engine coolant will leak from the timing cover if the gasket fails. Coolant leakage is also known to occur around the timing cover due to gaskets near the water pump that are prone to causing coolant leaks.

Gasket replacement is the only option for repair. Fortunately, gaskets are inexpensive and relatively simple to make if you are familiar with engines. A common sign of coolant leakage is constantly having to top up your coolant. Preventing overheating and severe engine damage requires keeping your 351W’s coolant level at the recommended level at all times.

Extra heat damages the 351W’s, and catastrophic engine failure is the most common result.

Coolant Leak Symptoms

  • Using more coolant than necessary
  • Water pump or timing cover coolant leaks
  • Overheating of the engine
  • There are times when leaks aren’t apparent, but a burning coolant smell is present.

2. Cracked Exhaust Manifolds – 351 Windsor

The engine block’s exhaust ports are connected to an exhaust manifold via bolts. The exhaust manifold collects exhaust air and sends it to the exhaust system, where it is released through the tailpipes. The exhaust manifold. Each of the 351W’s four cylinders is served by one of the engine’s two exhaust manifolds.

The 351 Windsor’s cast iron exhaust manifolds are a unique feature. During the heating and cooling process, cast iron expands and contracts in opposite directions. As the cast iron constantly expands and contracts as the engine warms up and cools down, it puts a great deal of strain on the material.

Heat cycles and constant engine vibration cause cracks in the exhaust manifolds, resulting in an exhaust leak over time. Beyond the harm to the environment, exhaust leaks can have a negative impact on a vehicle’s performance by causing a reduction in horsepower or acceleration.

Around 120,000 miles, the OEM manifolds on the 351W start to crack. Aside from replacing the manifolds or upgrading to performance manifolds, there isn’t much preventative maintenance available.

351W Cracked Exhaust Manifold Symptoms

  • Noise from the engine/exhaust in the cab is very loud.
  • Exhaust fumes in the vehicle’s cabin
  • A decrease in power and an increase in speed
  • Inefficient use of fuel

351 Windsor Exhaust Manifold Replacement Options

Since so many 351Ws were made, there should be no problem finding used parts. Because replacement parts for used/junk yard manifolds are readily available and inexpensive, many people opt to use them instead of purchasing new ones. However, the drawback is that any new set of OEM manifolds will need to be replaced sooner rather than later.

As a result, switching to steel exhaust headers from cast iron manifolds is a popular choice. headers have separate tubes for each cylinder that bolt to the exhaust manifold, whereas exhaust manifolds have one long tube that connects them all.

Cast iron exhaust manifolds are the only option for exhaust systems. Headers can boost output by 10-15hp, making them a popular choice among performance enthusiasts. However, they necessitate additional modifications to the exhaust system.

3. Gasket & Rear Main Seal Oil Leaks – Windsor 351

Along with the rear main seal oil leaks, I’d like to draw attention to general gasket oil leaks as another common issue. There are a number of gaskets in your engine that can deteriorate and leak as time passes.

That said, an old 351W that has not undergone a fresh rebuild or gasket repair is likely to leak oil or will do so in the future. Original gaskets rarely last more than 150,000 miles before they need to be replaced.

Gasket & Rear Main Seal Oil Leaks

For the time being, let’s focus on a more specific issue: oil leaks around the rear main seal. It is possible to find the rear main seal by looking at the engine’s crankshaft, which connects to the transmission. The small circular seal at the back of the engine is in charge of preventing oil leakage.

Oil leaks can occur if the 351W isn’t driven frequently enough, as the seal can dry out and crack over time. The seal is a small rubber part that is prone to deterioration as is common with any seal or gasket, and leaving the car sitting for some time can cause it.

This is a difficult project because the rear main seal needs to be replaced. The part costs a few dollars, but getting to the seal necessitates a significant amount of labor, making it an expensive repair bill if you aren’t handy with tools.

Rear Main Seal Oil Leak Symptoms

  • Oil leaking under transmission/back of engine
  • Quick oil consumption (frequent refills needed)

4. 351W Broken Intake Manifold

The intake manifold is located directly across from the exhaust manifold. The intake manifold is in charge of sending air from the intake to each cylinder of the engine. An exhaust manifold sits atop the engine block, and an air intake sits atop that manifold, allowing air to be drawn in and then distributed to the engine’s eight cylinders as needed.

Manifold bolts on the 351 Windsor are notoriously flimsy. Bolts mounted to the block are subject to high temperatures and the same heat cycles as the engine because of their location. Heat cycles, in combination with the constant vibration they experience, cause them to disintegrate.

Intake air leaks, also known as vacuum leaks, occur when the manifold bolts fail. If the engine’s air to fuel ratios are thrown off, various performance issues can occur, including a loss of power, slow acceleration, and cylinder misfiring..

This problem is easily fixed by swapping out the manifold bolts, fortunately. Check the manifold gasket while you’re at it to ensure it’s not leaking or isn’t damaged in any way.

351 Windsor Vacuum Leak Symptoms

  • Cylinder misfires
  • Lean/rich AFRs
  • Lack of power and acceleration
  • Bad fuel economy
  • Stuttering or hesitation under acceleration
  • Rough idling
  • Increased engine noise

5. 351W Weak Cylinder Blocks

I wanted to make performance enthusiasts aware of this, even though it isn’t necessarily a problem. The blocks produced between 1969 and 1971 are widely regarded as the strongest. The years from 1972 to 1974 were good as well, albeit not as good as the preceding ones.

Ford made a weight-saving change to the engine block castings in 1975. To achieve this, Ford reduced the amount of metal in the block, resulting in thinner block components compared to the older models’ thicker walls and more metal support.

351W Weak Cylinder Blocks

The newer blocks appear to be reliable up to about 650whp, although people have pushed the stock blocks to their limits. According to some reports, the stock block can produce 750-850whp. Some of the older blocks can handle power levels up to about 1000whp, while others can’t.

In today’s world, 351W engines are frequently modified, but this isn’t necessarily a bad thing. Be careful with the power levels you aim for and the block’s capabilities.

Ford 351 Windsor Reliability

The 351W Ford engines are nearly indestructible. Even on models from 1975 and later, the blocks are extremely robust and will not malfunction until a significant amount of power is added. The internal components, such as the pistons, rods, and other moving parts, are all incredibly sturdy.

The 351 Windsor is a tough engine that can withstand a lot of punishment. The engine’s block, internals, and even the head are in great shape, but these are already very old engines. Oil leaks, coolant leaks, seals, and water pumps are all common problems with old engines.

As they get older, the intake and exhaust manifolds both have a tendency to develop small problems. Aside from that, you won’t have too many engine-specific problems with these engines.

The most important thing to remember is to keep everything well-maintained. Coolant leaks and overheating are the two most common causes of engine failure in the 351W. Make sure you have an adequate cooling system for the 351 before you start modifying it.

The 351W engine’s major components should last well past the 300,000-mile mark if properly maintained and cared for.

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