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Ford 335 engine
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==400 and 351M== ===400===<!-- This section is linked from [[V8 engine]] --> By 1970 the 390 [[Ford FE engine|V8 FE engine]] was becoming outdated. With pending emission requirements, a more modern replacement was needed. Although the big-block 385 family was used to replace the larger displacement 428 [[Ford FE engine|V8 FE engine]], this engine family had nothing comparable in size to the 390 V8. For the 1971 model year, Ford introduced the 400 V8 engine as a replacement for the 390 V8.<ref name="V-8 Data Book"/><ref name="Ford Police">{{cite book|last=Sanow|first=Edwin|title=Ford Police Cars|date=1997|publisher=MBI Publishing|isbn=978-0-7603-0372-6|pages=63}}</ref> Ford billed the 400 as the 351C's big brother. It was designed to provide brisk acceleration in medium to heavy weight vehicles in an engine package that was smaller and lighter than the FE V8 Engines and the 385 Series Ford V8's.<ref name="bubba history"/> The Ford '''400''' engine was based on the 351 Cleveland but had a half-inch longer stroke than the 351 Cleveland. The 400 had "[[stroke ratio|square]]" proportions, with a 4.0 in (102 mm) bore and stroke. Ford called the engine a "400" but in actuality it [[engine displacement|displaced]] {{cvt|6590|cc|cuin L cc|1|order=out}}. To accommodate the longer stroke, Ford engineers increased the block deck height to 10.297 inches compared to the 351C's 9.206 inches.<ref name="V-8 Data Book"/><ref name="CC 351C pt2"/> As a result, the 400 used longer (6.580 inch) connecting rods than the 351C (5.778 inch), but it retained the same connecting rod-to-stroke (1.65:1) ratio as the 351C.<ref name="Cleveland"/> The 400 featured larger 3.00 inch main-bearing journals, the same size as those used in the 351 Windsor, but rod journals were the same size as the 351C.<ref name="V-8 Data Book"/> The cylinder heads for the 400 were the same as those used on the 351C-2V, having the open combustion chamber with smaller 2V-sized ports and valves. All 400s were low-performance engines that ran on regular fuel and all used a 2-barrel carburetor, a cast-iron intake manifold, and small port 2V cylinder heads. A 1-year only option 400 had flat top pistons,in 1971.<ref name="V-8 Data Book" /><ref name="CC 351C pt2"/><ref name="Bubba">{{cite web|title=Bubba's M-Block Engine Workshop|url=http://grantorinosport.org/BubbaF250/index.html|access-date=18 May 2014}}</ref> The 400 was designed as a high torque, low RPM engine that was a smaller, more efficient and lighter alternative for the big [[Ford 385 engine]]s, the 429 and 460, for use in Ford's medium and large size cars. Weighing just 80% of a similar big-block,<ref>{{cite web|last1=Farmer|first1=Dave|title=Weights and Sizes|url=http://www.gomog.com/allmorgan/engineweights.html|website=GoMoG Workshop Manual|access-date=3 June 2014}}</ref> it was originally available in Ford's [[Ford Custom|Custom]], [[Ford Galaxie|Galaxie]] and [[Ford LTD (North America)|LTD]] lines, and in [[Mercury Monterey]], [[Mercury Marquis|Marquis]], and [[Mercury Brougham|Brougham]] for the 1971 model year. For 1972, it was also available in the [[Ford Torino]], [[Mercury Montego]] and its variations through 1979. By the late 1970s it was also available in the [[Ford Thunderbird]], Ford F-series pickup trucks, the [[Lincoln Continental]], and [[Lincoln Continental Mark V|Mark V]]. Unlike the 351C, almost all 400 blocks used the large [[bell housing]] bolt pattern used by the [[Ford 385 engine|385 family]] big-block and were typically equipped with the higher torque-capacity [[Ford C6 transmission|C6 transmission]]. There were a small number of 400 block castings produced in 1973 with the dual bell housing patterns. It had the large bell housing and the small bell housing bolt pattern used by the small block V8 family and the 351C, though it was not necessarily drilled for both. These particular blocks have been dubbed the "400 FMX" by enthusiasts, though were never officially referenced as such by Ford.<ref>{{cite web |url=http://351cleveland.wetpaint.com/page/Block+400+FMX+ |title=Block 400 FMX - Clevelands Forever! |access-date=10 February 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130606165115/http://351cleveland.wetpaint.com/page/Block+400+FMX+ |archive-date=6 June 2013}}</ref> Most 400's also had unique engine mount bolt pattern but these 400 FMX blocks had provisions for both 351C-style and 400/351M engine mounts.<ref>{{cite web|title=400 FMX|url=http://351cleveland.wikifoundry.com/page/Block+400+FMX+|publisher=351Cleveland.net|access-date=20 May 2014}}</ref> For 1972, the compression ratio was reduced through the use of dished pistons. The compression was reduced again for 1973 and a new timing set retarded the camshaft timing 6° to aid with reducing emissions.<ref name="Bubba"/> Changes to the cylinder heads for 1975 to add the [[Thermactor]] emission system caused the exhaust port to be more restrictive than the earlier 1971-74 heads.<ref name="Bubba"/> The 400 was re-tuned by Ford in 1975 to use [[unleaded gasoline]] with the addition of catalytic converters to the exhaust system. An extra water jacket was added to the heads, along with further enlarging the combustion chamber to 80 cc.{{citation needed|date=January 2023}} The development of the 400 V8 led to a significant design flaw that remained with the engine throughout its production life. With a longer stroke, the compression ratio became excessively high with the 351-2V heads and flat top pistons. Ford engineers reduced the compression ratio by using a piston with a compression height that was too short and this led to an excessive deck clearance of 0.067" to .080" compared to a 351-2V at 0.035" .<ref name="bubba history"/><ref name="Build">{{cite book|last=Monroe|first=Tom|title=How to Rebuild Ford V8 Engines|date=1980|publisher=HP books|location=New York}}</ref> In 1971, this method of reducing compression was sufficient due to the higher-octane leaded fuels. However, once lower-octane unleaded fuels became used, the excessive deck clearance led to problems with detonation. For 1975, Ford dealt with this problem by decreasing the compression ratio further with a larger 15cc piston dish and reducing ignition timing. However, the 400 V8 obtained a reputation for being prone to detonation.<ref name="bubba history"/> Today, an array of performance parts are becoming more available for the "M" engines, with a resurgence of popularity in the classic truck market. ===351M=== {| class=wikitable align=right |+''Engine dimensions''<ref name="Cleveland"/> |- ! !!351C||400||351M |- !Nominal main bearing size |2.750 in (69.8 mm)||3.000 in (76.2 mm)||3.000 in (76.2 mm) |- !Rod length |5.78 in (146.8 mm)||6.58 in (167.1 mm)||6.58 in (167.1 mm) |- !Rod-to-Stroke Ratio |1.65:1||1.65:1||1.88:1 |- !Deck height |9.206 in (233.8 mm)||10.297 in (261.5 mm)||10.297 in (261.5 mm) |} When the 351 Cleveland was discontinued after the 1974 model year, Ford needed another engine in that size range, since production of the 351 Windsor was not sufficient. Ford took the 400 engine's tall-deck block and installed a crankshaft with a shorter {{cvt|3.5|in|0}} stroke to produce a {{convert|351|cuin|L|1}} engine. This crankshaft was not the same as a 351C, in that it used the larger {{cvt|3.0|in|0}} main bearing journals of the 400 V8.<ref name="V-8 Data Book"/> To compensate for the shorter stroke the pistons for the 351M have a taller compression height, so that it could use the same connecting rods as the 400. The result of the 351M using the longer 400 connecting rod was a higher connecting rod-to-stroke ratio of 1.88:1 than the 351C and 400's of 1.65:1.<ref name="Cleveland"/> Other than pistons and crankshaft the 351M shared all of its major components with the 400, and it also used the large [[Ford 385 engine|385 Series]] style bellhousing. The 351M was only ever equipped with a 2-barrel carburetor and open chamber small port 2V cylinder heads.<ref name="Bubba"/> 351M production began for the 1975 model year and blocks were cast in the Michigan Casting Center or the Cleveland Foundry. The 351M was the last pushrod V8 block designed by Ford<ref>{{cite web|url=http://400ford.info|title=Geoff Infield's Ford V8 page|access-date=25 July 2006|archive-url=https://web.archive.org/web/20060218205126/http://www.geocities.com/infieldg/v8main.html|archive-date=18 February 2006}}</ref> until the introduction of the 7.3-liter "Godzilla" engine for the Super Duty trucks in model year 2020.<ref>{{cite news |url=http://fordauthority.com/2019/08/ford-super-duty-7-3l-godzilla-v8-compares-heavy-duty-v8-engines-gm-ram/ |title=Ford Super Duty 7.3L Godzilla V8 vs. GM, Ram V8 Engines |first=Jonathan |last=Lopez |work=Ford Authority |location=US |date=8 August 2019 |access-date=5 October 2019}}</ref> ===Light truck usage=== For the 1977 model year, Ford replaced its [[Ford FE engine|FE]] big-block 360 and 390 engines in its light truck line with its new 351M and 400 engines. For light-truck use, a manual transmission could be ordered for the first time with these engines. As a result, the block was strengthened in the main bearing supports, in particular the #3 support to better handle the loads imparted by the clutch. The truck engines had unique parts including pistons for different compression ratios from the car engines, truck specific intake and exhaust manifolds, camshaft with more lift, and timing set that did not retard the camshaft timing. The strengthened engine block was introduced to the Ford cars for the 1978 model year.<ref name="bubba history">{{cite web|last=Resch|first=David|title=The 335 Engine Family|url=http://grantorinosport.org/BubbaF250/history/history03.html|access-date=19 May 2014}}</ref> ===Block-cracking problems=== The 400 V8s for the model years 1971–72 were either cast in the Dearborn Iron Foundry or the Cleveland Foundry. Those built for model years 1973–79 were either cast in the Cleveland Foundry or the Michigan Casting Center.<ref name="Bubba"/> The 351M introduced in 1975 shared the same block as the 400. The 351M and 400 blocks cast at the Michigan Casting Center prior to March 2, 1977, experienced water jacket cracking problems above the lifter bores. The cracking was (potentially) caused by an internal coring problem when the blocks were cast, although others considered it to be normal freeze cracking. The result was horizontal cracks approximately 1" above the lifter bore.<ref name="Build"/> After March 2, 1977, the blocks cast at Michigan Casting Center did not have problems with cracking. ===351M/400 identification confusion=== There exists debate as to what Ford meant by the "M" designation of the 351M. Some claim the "M" stands for “Modified” - being modified from a 400-V8 with a shortened stroke - though others claim that the "M" refers to the Michigan Casting Center, where the 351M began production. Some say that the "M" designation has no official meaning, and that it was just Ford's way of distinguishing the 351M from the 351C and 351W.<ref name="Bronco">{{cite web |title=History of the Ford 351M/400|url=http://www.projectbronco.com/History/history_of_the_ford_351m.htm|access-date=19 May 2014}}</ref> Ford master part catalogs reference the engine as a Modified.{{cn|date=June 2024}} Likewise, Ford's use of the 400 block in the creation of the 351M engine has resulted in the 400 mistakenly being referred to as the "400M" or "400 Modified." This is despite the 400 having been the design basis from which the "modified" 351M was derived and it was in production several years before Ford used the "M" designation. Further confusion arises from Ford printing "351M/400" on the emission stickers for the engine. The "351M/400" referenced the engine family, and some confused this with the engine name. This sticker also listed the engine displacement below the engine family. Ford's official name for the 400 V8 contains no additional designations - the proper nomenclature is simply "400." In the early 1970s before the 351M debuted, Ford referred to the 400 as the "400 Cleveland".{{citation needed|date=January 2023}} ===Replacement=== The 351M and 400 were last offered in a Ford passenger car in 1979. They remained available in Ford light-trucks until 1982. Reduced demand for larger engines due to tightening [[Corporate Average Fuel Economy|CAFE]] regulations led to the abandonment of the 351M/400 and the Cleveland production line. By 1980, mid-sized V8's had disappeared from the option list for almost all Ford cars. Only the full-size [[Ford Panther platform|Panther]] platform Fords had anything larger than 302 ci available, and this need was filled with the 351W. With low demand for engines in the size range of the 351M/400, the 335-series V8's no longer had a need to be produced. In addition, there were difficulties adapting the M-block to the second generation of emissions controls. Unlike previous Ford engines, [[Thermactor]] and [[exhaust gas recirculation]] features had already been built into the 351M and 400 engine, rendering adaptation to electronic feedback fuel/air systems difficult.<ref name="bubba demise">{{cite web|last=Resch|first=Dave|title=Demise of the M-Block|url=http://grantorinosport.org/BubbaF250/history/history04.html|access-date=22 May 2014}}</ref> One requirement of the second-generation equipment was an oxygen (O<sub>2</sub>) sensor in the exhaust, which had to be placed before the Thermactor air was added. Since Thermactor air was injected right into the block's exhaust ports in the M-block, there was nowhere for the O<sub>2</sub> sensor to go.
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