The 5 Most Frequent Ford 351 Windsor Engine Issues. Ford developed the 351 Windsor, a 5.8L small-block V8 engine, from 1968 to 1997. It is one of Ford’s most successful and longest-running engines. The 351W is a member of the Windsor V8 engine family, a colloquial term for engines manufactured in Windsor, Ontario. The Windsor family is a series of 90-degree OHV small-block V8 engines that were manufactured from 1961 to 2002.
The 351 Windsor is the largest V8 in the Windsor engine family, measuring 351 cubic inches (5.8L). The 351W saw numerous upgrades and enhancements over its nearly 30-year lifespan. While there are far too many to mention individually, here are some of the more noticeable changes over the years:
Because of the change in block casting in 1975, the 1969-1974 models are substantially stronger and thus more desired.
- In 1971, the deck height was increased to achieve a lower compression ratio.
- In 1984, the rear main seal was replaced to a one-piece design.
- In 1994, the speed density was replaced by MAF.
- Lifters were introduced in 1994.
- In 1988, the carburetor was replaced with fuel injection.
Ford vehicles that employ the 351 Windsor engine
- 1967-1970 Mustang
- Mercury Cougar, 1969-1970
- Ford Country Squire, 1969-1991
- Fairlane Fairlane 1969-1970
- Torino (1970-1976)
- From 1974 through 1976, Ford Elite
- Vans in the E-Series from 1975 to 1996
- LTD (1977-1982) / LTD II
- 1977-1979 Thunderbird
- 1979-1996 Ford Bronco
- 1979-1991 Crown Victim
- Ford F150/F250/F350 1987-1997
- Mercury Cougar Station Wagon, 1977-1979
- Mercury Colony Park from 1978 to 1986 and again from 1986 to 1991
- 1978-1982 The Mercury Marquis
- Mercury Grand Marquis, 1986-1991
- Continental Mark VI, 1980
351 Windsor takes against 351 Cleveland.
From 1969 through 1982, Ford developed the 351 Cleveland, a 5.8L, 351 cubic inch V8. Cleveland was given the name because of its manufacturing location in Cleveland, Ohio. Despite the fact that both engines are 5.8L V8, the 351 Windsor and 351 Cleveland are from separate engine families. The 351C, also known as the 351W and 351C, was a member of Ford’s “335” engine family.
When Ford recognized that demand for the 351 Windsor was higher than production capability in the Windsor facility, the 351 Cleveland was born. As a result, they decided to start producing 351s in the Cleveland factory as well. However, Ford also chose to boost the performance of the Cleveland-built 351s by installing a new cylinder head design. Two new head designs were created: one that was comparable to the 351W but had larger valves and ports, and another with huge ports and canted exhaust and intake valves.
To make matters even more complicated, the 351 Cleveland had several separate engine codes. Ford offered H, M, R, and Q versions of the 351C from 1970 to 1974, which were mostly performance focused versions of the regular 351C.
Performance enthusiasts frequently install 351 Cleveland heads onto 351 Windsor blocks to create a 351 Clevor. The Windsor blocks were known to be stronger, although the Cleveland heads had more flow and so more potential performance.
Common Engine Issues with the Ford 351 Windsor
- Coolant leaks at the timing cover
- Exhaust manifolds with cracks
- Oil and gasket leaks from the rear main seal
- Intake manifold bolts that have broken
- Weaker blocks (1975 and above)
A word of caution: many of these issues are caused by how old these engines are nowadays. The engines itself, including blocks, internals, and heads, are extremely sturdy and nearly bulletproof.
1. Coolant Leaks from the 351W Timing Cover
The timing chain on the 351 Windsor is protected by a cover that keeps dirt, mud, and grime off the chain and sprockets. And timing cover mounts to the front of the block and is gasket-sealed in situ.
The timing cover gasket tends to weaken and leak with time, as is common with gaskets. Engine coolant will leak around the timing cover if the gasket fails. Furthermore, the gaskets surrounding the water pump are known to create coolant leaks, resulting in coolant spilling around the timing cover.
The only option for repair is to replace the gaskets. Fortunately, the gaskets are inexpensive and rather simple to DIY provided you know your way around an engine. The most obvious sign of coolant leakage is regularly running out of coolant. Keeping your 351W’s coolant tank full is critical for avoiding overheating and significant engine damage.
The 351Ws do not tolerate high temperatures well, which is the most typical cause of catastrophic engine failure.
Symptoms of Coolant Leakage
- Excessive use of coolant
- Coolant leaking around the timing cover or water pump
- Overheating of the engine
- Occasionally, no leaks are detected, but a burning coolant odor is detected.
2. Exhaust Manifold Cracks – 351 Windsor
An exhaust manifold connects to the engine block’s exhaust ports. The manifold is in charge of collecting exhaust air and directing it to the exhaust system, where it is expelled through the tail pipes. The 351W has two exhaust manifolds, one for each cylinder.
The 351 Windsor’s exhaust manifolds are built of cast iron. When cast iron is heated, it expands, and when it cools, it contracts. Engine heat cycles, or the engine constantly warming up and cooling down, put a lot of strain on the cast iron since it is always expanding and contracting. Heat cycles and persistent engine vibration cause the manifolds to crack over time, resulting in an exhaust leak. Aside from the negative environmental impact of exhaust leaks, it can cause a variety of performance concerns such as power loss or acceleration.
The 351W’s OEM manifolds are known to fracture around 120,000 miles. Outside of replacing the manifolds ahead of time or upgrading to performance manifolds, there isn’t much in the way of preventative maintenance.
Symptoms of a Cracked Exhaust Manifold on a 351W
- Loud engine/exhaust noise coming from the cab
- Exhaust gas odor from within the cab
- Acceleration and power loss
- Inadequate fuel economy
Options for 351 Windsor Exhaust Manifold Replacement
Because of the large number of 351Ws produced, used parts should be plentiful. It is popular to replace manifolds using used/junk yard manifolds because the parts are often easy to find and inexpensive to replace. The disadvantage is that any set of OEM manifolds will most likely crack again.
Having said that, upgrading from cast iron manifolds to steel exhaust headers is a common choice. Headers differ from exhaust manifolds in that they include a separate steel tube that bolts up to each cylinder before joining into a single connector tube. Exhaust manifolds are made of solid cast iron. Headers can enhance power by 10-15hp, making them a popular modification for performance fans, albeit they will necessitate additional exhaust system changes.
3. Oil Leaks from the Gasket and Rear Main Seal – Windsor 351
Along with the rear main seal oil leaks, I’d like to include general gasket oil leaks as a generally common problem. The head gasket, water pump gasket, timing cover gasket, and so on all deteriorate and leak with age. That being said, any old 351W that hasn’t had a fresh rebuild or gasket repairs is likely to leak oil or will do so in the future. Gaskets rarely last more than 150,000 miles, especially if they are originals.
Moving on to the more specific issue, the rear main seal is prone to oil leaks. The rear main seal is positioned in the engine’s back end, where the crankshaft meets the transmission. The little circular seal prevents oil from seeping out the back of the engine.
When the 351W isn’t driven on a regular basis, the seal can dry out and produce cracks, allowing oil to leak out. While allowing the car to sit for a while can cause this, it is also typical on frequently driven cars because the seal is a small rubber part that is prone to deterioration, as is the case with any seal or gasket.
Unfortunately, changing the rear main seal is a time-consuming task. The part is only a few dollars, but it needs substantial labor to get to the seal, making it a pricey repair bill if you aren’t capable of DIY’ing the project.
Symptoms of a Rear Main Seal Oil Leak
- Oil leaking from the transmission/engine back end
- Quick oil consumption (refills required frequently)
4. 351W Intake Manifold Crack
The intake manifold is located opposite the exhaust manifold. The intake manifold is in charge of directing air from the intake to each of the engine’s cylinders. The manifold is situated on top of the block, and the intake sits on top of it, where air is sucked in and distributed to each of the eight cylinders.
The manifold bolts on the 351 Windsor are prone to breaking. Because the bolts are attached to the block, they are subject to high temperatures and the same heat cycles as the engine. They break off due to the impacts of heat cycles combined with the continual vibration they endure.
When the manifold nuts fail, intake air leaks out, which is also known as a vacuum leak. This can throw off the engine’s air-to-fuel ratios, resulting in a variety of performance difficulties such as power loss, lack of acceleration, cylinder misfires, and so on.
Fortunately, changing the manifold bolts solves the problem. While you’re at it, check the manifold gasket to make sure it’s still intact and not leaking.
Symptoms of 351 Windsor Vacuum Leak
- Misfires in the cylinders
- AFRs that are lean/rich
- Inadequate power and acceleration
- Poor fuel economy
- Under acceleration, stuttering or hesitation
- Idling in a rough manner
- Engine noise has increased.
- Weak Cylinder Blocks 351W
While this isn’t necessarily a concern, I wanted to bring it to the attention of performance aficionados. The 1969-1971 blocks are regarded as the most powerful. 1972-1974 were also strong years, albeit slightly less so than the prior ones.
Ford altered the block castings in 1975 to achieve a lower weight block. To do this, Ford reduced the amount of metal utilized in the block, making various components of the block thinner in comparison to prior models, which were thicker and had more metal support.
While individuals are pushing higher power on the stock blocks, the newer blocks appear to be reliable up to 650whp. We’ve heard that the stock block can produce 750-850whp. The older blocks appear to be capable of managing power levels approaching 1000whp.
While this isn’t always a concern, 351W engines are frequently modified in today’s environment. Be wary of the power levels you aim for and the capabilities of the block you have.
The Reliability of the Ford 351 Windsor
The 351W engines from Ford are virtually bulletproof. Even on 1975+ vehicles, the blocks are very strong and will not cause any difficulties until considerable power is introduced. Rods, pistons, and other internal components are also rock solid.
Overall, the 351 Windsor is a robust engine that is built to last. While the block, internals, head, and other major components are all in good shape, keep in mind that these engines are growing old. Given the age of these engines, oil leaks, coolant leaks, work gaskets and seals, water pumps, and so on are all prone to breakdown. Due to age, both the intake and exhaust manifolds tend to develop small difficulties. Otherwise, you won’t encounter many engine-specific troubles with these engines.
Proper maintenance is always essential. Because heat is the most lethal enemy of the 351W engine, controlling coolant leaks and engine overheating is critical to reliability. If you intend to modify the 351 engine, make sure you have a suitable cooling system in place to prevent excessive engine heat.
The core components of the 351W engine should be able to exceed 300,000 miles with adequate maintenance and care.