Editing Ford small block engine (section)

==Overview==
The small-block V8 engine was introduced in the 1962 Ford Fairlane and Mercury Meteor cars. Displacing {{cvt|221|cuin|L|1}}, it was designed to save weight, using thin-wall casting for a short-skirt block that does not extend below the centerline of the crankshaft. The engine uses a separate aluminum timing chain cover, which differentiates it from the later Ford 335-series engines that use an integrated timing cover. All Ford small-block engines use two-valve-per-cylinder heads, with "2V" and "4V" designations indicating the number of barrels (or venturi) in the [[carburetor]]. The valves are in-line and use straight, six-bolt valve covers. Coolant is routed out of the block through the intake manifold.

The design was soon bored to {{cvt|260|cuin|L|1}} and again to {{cvt|289|cuin|L|1}}, then stroked to {{cvt|302|cuin|L|1}}, settling on the most common displacement offered until the engine's retirement in 2001, nearly 40 years after the basic block design debuted. Two additional displacements were produced during the engine's history. A {{cvt|351|cuin|L|1}} model was offered from 1969 until 1996. The 351W (so named to distinguish it from the 335-series Cleveland-produced 351C) has a taller deck height than the other engines in the series to avoid excessively short connecting rods. And for a brief time in the early 1980s, a version with a smaller bore diameter that displaced {{convert|255|cuin|L|1}} was produced as Ford struggled with emissions and fuel economy.

In response to the [[Chevrolet Camaro]]'s success in the [[SCCA]] Trans-Am Series, Ford engineers developed a new racing engine from the small block. The first attempt mated a tunnel-port head to a 289 cubic inch block, but the displacement proved to be too small to deliver the desired power. The next iteration of the engine mated an improved head design to the 302 cubic inch block, producing the famous "[[Ford Boss 302 engine|Boss 302]]". The heads from the Boss 302 became the production heads on the 335-series {{cvt|351|cuin|l|0}} "Cleveland" engines, which used the same bore spacing and head bolt configuration as the small block engines.

As the 1980s drew to a close, Ford began designing a new [[OHC]] V8 to replace the small block. The [[Ford Modular engine|Modular 4.6&nbsp;L OHC V8]] debuted in the 1991 Lincoln Town Car, signaling the eventual demise of the OHV Ford small-block. Through the rest of the decade, Ford gradually shifted V8 applications to the Modular engine, with the Mustang transitioning in 1996. Even as the small-block neared the end of its life, development continued, with new cylinder heads introduced for the Ford Explorer in 1997. American sales in new vehicles ended with the 2001 Ford Explorer, but the engine continues to be offered for sale as a crate engine from Ford Racing and Performance Parts.

===Design changes===
All 221, 260, and 289 engines built from July 1961 through August 1964 used a five-bolt bell housing, with all 221s and 260s being of this configuration, while 289s made after August 1964 changed to the six-bolt pattern – a change made to resolve transmission utilization issues, such as the need for larger-diameter clutches.

The block mount pads and the cylinder wall contour of the 221 and 260 engines changed in January–February 1963 with the introduction of the 289 variant – all 221 and 260 engine blocks up to this time featured "corrugated wall" construction with two [[core plug]]s on the side of each bank and engine mount hole pitch distances of 6 inch.

All three block variants from this point on featured the straight wall method of construction, three core plugs, and an engine mount hole pitch distance of seven inches. The corrugated wall method of block construction had caused cleaning difficulties in the foundry from day one and a change was phased in.