Ford 335 engine
The Ford 335 engine was a family of engines built by the Ford Motor Company between 1969 and 1982. The "335" designation reflected Ford management's decision during its development to produce a engine with room for expansion. This engine family began production in late 1969 with a 351 cu in engine, commonly called the 351C. It later expanded to include a 400 cu in engine which used a taller version of the engine block, commonly referred to as a tall deck engine block, a 351 cu in tall deck variant, called the 351M, and a 302 cu in engine which was exclusive to Australia.
The 351C, introduced in 1969 for the 1970 model year, is commonly referred to as the 351 Cleveland after the Brook Park, Ohio, Cleveland Engine plant in which most of these engines were manufactured. This plant complex included a gray iron foundry, and two engine assembly plants. As newer automobile engines began incorporating aluminum blocks, Ford closed the casting plant in May 2012.
The 335 series engines were used in mid- and full-sized cars and light trucks, at times concurrently with the Ford small block family 351 Windsor, in cars. These engines were also used as a replacement for the FE V8 family in both the car and truck lines. The 335 series only outlived the FE series by a half-decade, being replaced by the more compact small block V8s.
Overview
The 335-series V8s were overhead valve V8 engines that used a unique short-skirt engine block that was both longer and heavier than that of the existing Ford small block V8. The 335 series incorporated features used on the 385 big-block series, including the canted valve layout, the valve train design, and thin-wall casting technology. All 335 series V8s had free breathing, large-port canted valve heads with a rugged engine block. These engines use a shallow poly angle combustion chamber rather than the wedge style used on the small blocks. The 335 engines use large main-bearing caps, with two-bolt as standard and four-bolt added on some performance versions.The first engine in the 335 series was introduced in late 1969 as the 351C. The 400 cu in appeared in the third quarter of 1970, which raised deck height from and tall deck to accommodate a longer stroke, and used larger main bearings for additional strength. This was similar to the changes made to convert a 302 Small Block to the 351 Windsor.
For the 1975 model year the 351M replaced the 351C in North American markets. Initially Ford of Australia imported US made 351C engines. However, by November 1971, Ford of Australia began to manufacture the 351C locally at the Geelong Foundry. This engine was very similar to the American counterpart and remained in production until December 1981. Ford of Australia also produced a smaller 302C alongside the 351C, which was exclusive to the Australian market.
Comparison to Ford Small Block V8
All 335 series engines shared the same bore spacing and cylinder head bolt pattern as the Small Block V8 family. There are a number of significant differences between the two engine families. The 335 series have a roughly two-inch extension cast into the front of the block which forms an integrated timing cover enclosure covered by a piece of flat steel, similar to an Oldsmobile V8 engine. This results in the 335 series engine block being heavier than the Small Block series engines'. The 335 series use a dry intake manifold with the radiator hose connecting vertically to the cylinder block above the cam timing chain cover. Small Blocks use a wet intake manifold which routes coolant through the intake manifold via a horizontally protruding hose. The 335 uses smaller, 14mm, spark plugs and has a square-shaped eight bolt rocker cover while the small block's six-bolt rocker cover is more rounded.Oil system
To reduce production costs, Ford eliminated one of the 335 series's main oil galleries from the block casting, leaving two compared to the Small Block family's three. The result was an oil system very similar to the 385 series V8s, adequate for street engines but falling short in high-revolution race use without modification. The two main oil galleys in the 335 series engine run along the lifter bores. Oil is fed from the filter to the number one main bearing followed by the number one cam bearing above. At the same time, it also feeds the right hand oil galley, supplying the right side lifter bank. It has four galleries that lead to each of the remaining main bearings. After the oil feeds them, it feeds each corresponding camshaft bearing above. At the rear-most main bearing, the oil goes into the second gallery, which feeds the left lifter bank. In addition the oil system not prioritizing the main bearings, the 335 engines have excessive clearances in the lifter bores. This results in oil leaking out of the lifter bores which can cause oil cavitation from the lifter motion, and can reduce oil flow to the main bearings.Cylinder heads
The cylinder-head design for the 335 series engines is its most definitive design feature. All cylinder head variants were two-valve that use large free flowing ports with poly-angle or 'canted' valves. Having the intake and exhaust valves at separate angles allowed for very large valves to be used while reducing the port length and minimizing sharp turns within it, creating freer flowing heads than the Ford small block V8s.The 335-series engines used different cylinder heads for two and four barrel carburetors. The 2V small port cylinder heads were used on 2-barrel engines while the 4V large port cylinder heads were used on the 4-barrel engines. The ports and valves on 2V heads were significantly larger than small block engines and had excellent flow - actually slightly better than 4V heads at lower valve lifts. The 4V heads had enormous ports which flowed very well, in particular at higher valve lift, and could out-flow Chevrolet Double Hump heads and Chrysler's high-performance 340 heads.
In addition to the two port sizes, the 335 cylinder heads used two style of combustion chambers, an open or a closed "quench" chamber. Both combustion chambers are very shallow, due to the shallow valve angles. The combustion chambers are almost a very shallow hemispherical chamber, rather than a wedge shaped. The closed chamber heads enclose the valves more closely, reducing combustion chamber volume, to increase the compression ratio. However, both designs have the same thermal efficiency and resistance to detonation. The closed combustion chamber promotes better swirling of incoming air fuel mixture, giving it a low-rpm torque advantage, and requires less machining to obtain high compression ratios. However, the open chamber heads valves are less shrouded, which improves low lift airflow, and they exhibit better emissions characteristics.
Most 335 series engines used stamped rocker arms with cast fulcrums that made for a non-adjustable valve train. The rocker arm design was originally used by the Ford 385 series engines. However, the Boss 351 and 351 HO had an adjustable valve train, using rocker arms mounted on screw-in studs and guide plates.
Prior to the release of the 351C, the 335 Series cylinder head was used on the Ford Boss 302 engine. The Boss 302 used a large port closed chamber 4V cylinder head which required minor modifications to make the cylinder heads work with the 302 engine block. The Boss 302 version of the cylinder heads used small 58cc cambers and large 2.23" intake valves. The valves were later reduced to 2.19" as used on the 351C 4V cylinder heads.
| Head type | Chamber type | Chamber volume | Intake valve | Exhaust valve | Intake port | Exhaust port | Application |
| 2V | Open | 74.7 - 79.9cc | 2.04" | 1.65" | 2.02" x 1.65" | 1.84"x1.38" | 351C-2V, 351M, 400 |
| 4V | Closed | 61.3 - 64.3cc | 2.19" | 1.71" | 2.50" x 1.75" | 2.00"x1.74" | 1970 351C-4V |
| 4V | Closed | 64.6 - 67.6cc | 2.19" | 1.71" | 2.50" x 1.75" | 2.00"x1.74" | 1971 351C-4V |
| Boss 351 | Closed | 64.6 - 67.6cc | 2.19" | 1.71" | 2.50" x 1.75" | 2.00"x1.74" | 1971 Boss 351 |
| 351C-CJ | Open | 73.9 - 76.9cc | 2.19" | 1.71" | 2.50" x 1.75" | 2.00"x1.74" | 1971-72 351C-CJ |
| 351C HO | Open | 73.9 - 76.9cc | 2.19" | 1.71" | 2.50" x 1.75" | 2.00"x1.74" | 1972 351C HO |
| 351C-CJ | Open | 73.9 - 76.9cc | 2.04" | 1.65" | 2.50" x 1.75" | 2.00"x1.74" | 1973-74 351C-CJ |
| Australian 302C | Closed | 56.4 - 59.4cc | 2.04" | 1.65" | 2.02" x 1.65" | 1.84"x1.38" | 302C |
351 Cleveland
History
The genesis of the "351 Cleveland" resulted from Ford's inability to produce enough of its new Ford small block engine-based 351 cu in V8s at its Windsor Engine Plant #1 in Windsor, Ontario, Canada. Sales and marketing forecasts for the 1969 model year called for a second line, which was organized at Ford's Cleveland, Ohio, engine works.At this time, it was also decided to upgrade the design of the new Cleveland manufactured 351s to improve performance. Two cylinder-head designs were developed, one similar to the 351W, but with larger ports and valves, and the other with very large ports with canted intake and exhaust valves similar to the big-block Ford 385 series V8. Sales, marketing, and product planning favored the canted valve design, as it was viewed as more innovative.
Other changes to the engine were related to ease of manufacture and improved reliability. This led to elimination of coolant flowing through a 'dry' intake manifold, a potential source of leaks and minimized unnecessary heat transfer. To perform this change, the front of the engine block was extended to include provisions for the coolant to flow through a crossover in the block. This extension also acted as an integrated timing chain housing. The timing chain housing was covered with flat steel that was easier to seal than the typical large timing chain cover used on other Ford V8s. These changes resulted in a bigger and heavier engine block than the small block V8s. To help reduce costs the oil system was revised, as explained above. Although the 351W began as the basis for the 351C, by the time it reached production the design changes resulted in almost no parts interchanging between the two designs. The two engines, however, shared the same bore spacing, engine mounts and bell housing pattern.
The 351 Cleveland began production in July 1969 for the 1970 model year. Its actual displacement was. A conventional two-barrel "2V" version and a four-barrel "4V" performance version were built. The 351C-2V was never marketed as a high-performance engine. It used the small port 2V cylinder heads with open combustion chambers to produce a more economical passenger car engine that was tuned more for low-rpm torque. The 351C-4V was marketed as a high-performance engine, featuring the 4V large ports heads with closed "quench" combustion chambers. Later versions of the 351C with 4V heads continued to use the large ports and valves, but switched to open chamber heads in an effort to reduce engine emissions. Only the Q-code 351 "Cobra Jet", R-code "Boss" 351, and R-code 351 "HO" versions have four-bolt main bearing caps, however, all 335 series engines could be modified to have 4-bolt main bearing caps.