Ford 4.6L 2/3/4-valve V8 Engine Specs, Problems & Reliability

The Ford 4.6L V8 engine, the first member of Ford's Modular overhead camshaft engine family in production, was introduced in the 1991 Lincoln Town Car. It was a 4.6-liter, 90-degree V-angle, eight-cylinder gasoline engine with two valves per cylinder and SOHC design. Later, this engine became the base V8 in the Mustang GT. Ford has also produced a 4-valve DOHC version well known for SVT Cobra and Mach 1 applications. This 32-valve DOHC 4.6L engine debuted in the 1993 Lincoln Mark VIII under the name 4.6L Four-Cam V8. The new Modular 4.6-liter V8 series replaced its pushrod-based predecessor, Ford's Small Block 5.0 H.O. engine.

Ford's 4.6L V8 has a deep-skirt aluminum or cast iron cylinder block (Romeo and Windsor castings), depending on model year and application. While Windsor iron blocks have "W" letters and dowel pins at the cross-bolted main caps, Romeo 4.6 iron blocks have jackscrew cross-bolted main caps and are identified by "R" (but not all of them). Otherwise, they look the same. Aluminum cylinder blocks were cast at the Windsor Aluminum Plant (WAP) with the exception of older 90s Teksid blocks, which were cast in Turin, Italy. Aluminum blocks came with 6-bolt main bearing caps.

The angle between the cylinder banks is 90 degrees. Deck height is 8.937 in (227.0 mm), and cylinder bore spacing measures 3.937 in (100.0 mm). The engine block features a nearly 1:1 bore-to-stroke ratio (square configuration) that positively affects its noise, harshness, and vibration characteristics. The connecting rod length is 5.933 inches (150.7 mm). Modular engines were equipped with six- or eight-bolt crankshafts. Eight-bolt steel crankshafts were used in truck and high-performance applications, while six-bolt crankshafts were usually fitted in Romeo blocks under the hoods of passenger cars. All engines came with forged pistons and cracked, powdered metal connecting rods from the factory.

The 4.6 engine can be fitted with three types of aluminum cylinder heads: 2-valve (1990-2014), 3-valve (2005-2010) with a single overhead camshaft (SOHC) valvetrain, and 4-valve with a dual overhead camshaft configuration. Single camshafts, as well as individual intake and exhaust camshafts in the four-valve version, are driven by two timing chains (one for each head). The valvetrain for all of them features low-friction roller rocker arms and hydraulic lash adjusters. The 3-valve cylinder head features apex-shaped combustion chambers with a centralized spark plug, two intake valves, and one large exhaust valve designed to improve velocity and volume. 4.6 3V SOHC engines were also equipped with Ford's variable camshaft timing (VCT) system. Ford 4.6 2v/3v engines feature an intake manifold made of composite material.

All 32-valve 4.6L DOHC engines had aluminum blocks only (except 2003-2004 SVT Cobra, which had an iron block with 4-bolt main bearing caps). Each cylinder has two intake and two exhaust valves. The 1993-1998 four-valve heads feature an individual intake port for each intake valve (split-port design). In 1999, cylinder heads were revised, and engineers implemented tumble-style intake ports where one intake port feeds two intake valves. In that year, they also replaced the variable runner-length intake manifold with a fixed runner-length intake manifold and changed camshaft profiles.

Modular 4.6L V8s had a traditional sequential multi-port fuel injection system controlled by the ECU and mechanical/electronic throttle body. They were also fitted with an electronically controlled, individual coil-on-plug ignition system.

The 4.6-liter 4-valve V8 engine featured on Ward's 10 Best Engines List for 1996 and 1997 years, while the 3-valve version was on the list for 2005-2008 and received a variety of accolades. Using this engine as a base, Ford developed a bigger 5.4-liter engine series, which also gained good success in sales. The production of the 4.6L Modular engine was discontinued in 2014. The last engine in the line was a 4.6-liter 2V engine for a 2014 model-year Ford E-Series van. By that time, the new Modular 5.0L Coyote engine, its successor, had already been produced for 3 years.

Engine Specs

Ford 4.6 V8 Modular Engine Problems and Reliability

Ford's Modular 4.6 V8 has earned a highly positive reputation amongst owners in terms of reliability and longevity. The engine can easily run well over 200,000 miles. Some taxi services used Crown Victorias with 4.6 V8s until impressive 300,000 or even 400,000 miles. But of course, ideal engines do not exist, and this engine has several common problems and design flaws that are currently widely known.

The first widespread problem is plastic intake manifold cracking. This problem can be found in 4.6L SOHC 2-valve engines produced from 1996 to 2001. In that period, Ford used a nylon composite intake manifold manufactured by DuPont. This manifold was prone to failure without any warning or sign. The reason is that the intake manifold could not handle stress on the material caused by thousands of heating and cooling cycles (expansion and contraction) and additional forces and vibrations coming from the alternator bracket mounted right into the plastic. As a result, this manifold can crack and split, and the heater hose and coolant temperature sensor can loosen, which would result in an engine coolant leak and vehicle overheating. Late in 2001, Ford replaced the all-plastic manifold with a revised intake manifold that uses cast aluminum at the failure points.

A short thread depth in the aluminum cylinder heads is the root of the second common problem: stripping of cylinder head spark plug threads. Be careful while changing spark plugs on any Ford 4.6 V8s, as it is so easy to over-torque them and strip threads. Ford recommends a threaded insert as the method to repair stripped thread and even provides a tool kit specifically for that.