Editing Chevrolet big-block engine (section)

==Mark I (W-series)==
The first version of the "big-block" V8 Chevrolet engine, known as the W-series, was introduced in 1958.<ref>{{Cite web |title=Chevy Big Block vs Small Block |url=https://www.classicmuscleparts.com/resources/chevy-big-block-vs-small-block}}</ref> Chevrolet designed this engine for use in passenger cars and light trucks. This engine had an [[overhead valve]] design with offset valves and uniquely scalloped [[valve cover]]s, giving it a distinctive appearance. The W-series was produced from 1958 to 1965, in three [[engine displacement|displacements]]:
* {{cvt|348|cuin|L|1}}, available from 1958 to 1961 in cars, and in light trucks through 1964;
* {{cvt|409|cuin|L|1}}, available from 1961 to 1965; and
* {{cvt|427|cuin|L|1}}, available in 1962 and 1963.

The W-series engine was made of [[cast iron]]. The engine block had {{convert|4.84|in|mm|adj=on}} bore centers, two-bolt [[main bearing]] caps, a "side oiling" [[Motor oil|lubrication system]] (the main oil gallery located low on the driver's side of the crankcase), with full-flow oil filter, and interchangeable [[cylinder head]]s. Heads used on the high performance 409 and 427 engines had larger ports and valves than those used on the 348 and the base 409 passenger car and truck engines, but externally were identical to the standard units – but for the location of the engine oil dipstick, on the driver's side on the 348 and the passenger's on the 409/427. No satisfactory explanation was ever offered for why this change was made, but it did provide a reliable means of distinguishing a 348 from the larger engines.

As with the {{cvt|265|and|283|cuin|L|1}} "small-block" engines, the W-series [[poppet valve|valve]] gear consisted of tubular steel [[pushrod]]s operating stud-mounted, stamped-steel rocker arms. The push rods also acted as conduits for oil flow to the valve gear. Due to the relatively low mass of the valve train, mechanical lifter versions of the W-series engine were capable of operating at speeds well beyond 6000 [[revolutions per minute|rpm]].

The [[combustion chamber]] of the W-series engine was in the upper part of the [[cylinder (engine)|cylinder]], not the head, the head having only tiny recesses for the valves. This arrangement was achieved by combining a cylinder head deck that was not perpendicular to the bore with a crowned [[piston]], which was a novel concept in American production engines of the day. As the piston approached [[top dead center]], the angle of the crown combined with that of the head deck to form a wedge-shaped combustion chamber with a pronounced quench area. The spark plugs were inserted vertically into the quench area, which helped to produce a rapidly moving flame front for more complete combustion.

The theory behind this sort of arrangement is that maximum [[mean effective pressure|brake mean effective pressure (BMEP)]] is developed at relatively low engine speeds, resulting in an engine with a broad [[torque]] curve. With its relatively flat torque characteristics, the "W" engine was well-suited to propelling both the trucks and heavier cars that were in vogue in the US at the time. The W-series was a physically massive engine when compared to the "small-block" Chevrolet engine. It had a dry weight of approximately {{convert|665|lb|kg|0}}, depending on the type of [[intake manifold]] and carburetion systems present. It was 1.5 inches longer, 2.6 inches wider, and 0.84 inches shorter than the 283 "small-block".<ref>"Engineering the 'W' Engine – Chevrolet's 348-cu-in. V8." SAE Transactions, Volume 67 (1959), 103.</ref>

General Motors engineers explained, in 1959, reasons behind the combustion-in-block setup. Anticipating varied future compression ratios in future auto and truck use: "It was obvious that with the combustion chamber placed within the cylinder head, the foundry must retool every time a compression change is in order. The necessity of making special heads to provide a range of compression ratios and to permit attachment of accessory mountings for the various model applications is of serious concern to the manufacturing and service departments ... Inclining the top of the block to 16° and shaping the top of the piston like a gabled roof with a 16° angle resulted in a 32° wedge-shaped combustion space ... The addition of two milled cutouts [in the head] to extend the volume of the combustion wedge can create a compression ratio of 7.5:1; one milled cutout produces a 9.5:1 compression ratio. The difference between the volume of these cutouts provides a wide compression range without making any changes in the piston or cylinder head. The number or size of cutouts is varied simply by adding or removing cutters."<ref>"Engineering the 'W' Engine – Chevrolet's 348-cu-in. V8." SAE Transactions, Volume 67 (1959), 104–105.</ref>

===348===
The first iteration of the W-series engine was the 1958 "Turbo-Thrust" {{convert|348|CID|L|1|adj=on}}, originally intended for use in Chevrolet trucks but also introduced in the larger, heavier 1958 passenger car line. Bore and stroke was {{cvt|4+1/8|x|3+1/4|in|mm|1}}, resulting in a substantially [[oversquare]] design. This engine was superseded by the {{cvt|409|cuin|L|1}} as Chevrolet's top performing engine in 1961 and went out of production for cars at the end of that year. It was produced through 1964 for use in large Chevrolet trucks.

[[File:348 W Block.jpg|thumb|1958 348 4-barrel engine]]

With a four-barrel [[carburetor]], the base Turbo-Thrust produced {{cvt|250|hp|kW|0}}. A special "[[Tri power]]" triple-two-barrel version, called the "Super Turbo-Thrust", produced {{cvt|280|hp|kW|0}}. A "Special Turbo-Thrust" upped the power output to {{cvt|305|hp|kW|0}} with a single large four-barrel carburetor. Mechanical lifters and Tri power brought the "Special Super Turbo-Thrust" up to {{cvt|315|hp|kW|0}}. For 1959 and 1960, high-output versions of the top two engines were produced with {{cvt|320|hp|kW|0}} and {{cvt|335|hp|kW|0}} respectively. In 1961, power was again increased to {{cvt|340|hp|kW|0}} for the single four-barrel model, and {{cvt|338|hp|kW|0}} when equipped with Tri power.

{| class="wikitable"  style="float:center;"
|+Versions
!First Year
!Last Year
!Model Name
!Features
!Power (Advertised [[Horsepower#SAE gross power|Gross]])
|-
|rowspan="4"|1958||rowspan="3"|1961||Turbo-Thrust||4 barrel||{{cvt|250|hp|0}}
|-
|Super Turbo-Thrust|| 3x2 barrel||{{cvt|280|hp|0}}
|-
|Special Turbo-Thrust||4 barrel||{{cvt|305|hp|0}}
|-
|rowspan="2"|1960||Special Super Turbo-Thrust|| 3x2 barrel||{{cvt|315|hp|0}}
|-
|rowspan="2"|1959||Special Turbo-Thrust||4 barrel||{{cvt|320|hp|0}}
|-
|rowspan="3"|1961||Special Super Turbo-Thrust|| 3x2 barrel||{{cvt|335|hp|0}}
|-
|rowspan="2"|1960||Special Turbo-Thrust||4 barrel||{{cvt|340|hp|0}}
|-
|Special Super Turbo-Thrust|| 3x2 barrel||{{cvt|348|hp|0}}
|}

===409===
[[File:409Dual4Barrel.jpg|alt=409 Cubic Inch Engine|thumb|409 Cubic Inch Engine. Dual 4 Barrel 409 hp version]]
A {{cvt|409|CID|L|1}} version was Chevrolet's top regular production engine from 1961 to 1965, with a choice of single or 2X4-barrel [[Rochester Products Division|Rochester]] [[carburetor]]s. [[Bore (engine)|Bore]] x [[Stroke (engine)|stroke]] were both up from the {{cvt|348|CID|L|1}} to {{cvt|4.31|x|3.5|in|mm|1}}. On December 17, 1960, the 409 engine was announced along with the [[Chevrolet Impala (third generation)|Impala SS (Super Sport)]] model. The initial version of the engine produced {{cvt|360|hp|kW|0}} with a single 4-barrel [[Carter Carburetor|Carter AFB]] carburetor. The same engine was upped to {{cvt|380|hp|kW|0}} in 1962. A {{cvt|409|hp|kW|0}} version of this engine was also available, developing 1&nbsp;hp per cubic inch with a dual-snorkle [[intake manifold]] and dual aluminum four-barrel Carter AFB carburetors. It had a [[forged steel]] [[crankshaft]].<ref>{{cite web|url=http://auto.howstuffworks.com/chevy-409-cid-v-8-engine1.htm |title=Chevy 409-cid V-8 Engine Overview|website=HowStuffWorks|publisher=Auto.howstuffworks.com |date=2008-04-24 |access-date=2012-05-31|archive-url=https://web.archive.org/web/20120312084059/http://auto.howstuffworks.com/chevy-409-cid-v-8-engine1.htm|archive-date=March 12, 2012}}</ref> This dual-quad version was immortalized in [[the Beach Boys]] song titled "[[409 (song)|409]]".

In the 1963 model year, output reached {{cvt|425|bhp|PS kW|0}} at 6000&nbsp;rpm and {{cvt|425|lbft|Nm|0}} at 4200&nbsp;rpm of [[Machine torque|torque]] with the Rochester 2X4-barrel carburetor setup, a [[compression ratio]] of 11:1 and [[tappet|solid lifters]].<ref>{{cite web|url=http://www.automobile-catalog.com/car/1963/380420/chevrolet_impala_sport_coupe_409_v-8_turbo-fire_425-hp_4-speed_close.html|title=1963 Chevrolet Impala Sport Coupe 409 V-8 Turbo-fire 425-HP 4-speed close|website=automobile-catalog|access-date=July 1, 2018}}</ref> The engine was available through mid-1965, when it was replaced by the {{cvt|396|CID|L|1}} {{cvt|375|hp|kW|0}} Mark IV big-block engine. In addition, a {{cvt|340|hp|kW|0}} version of the 409 engine was available from 1963 to 1965, with a single 4-barrel [[cast iron]] intake mounting a Rochester 4GC square-bore carburetor, and [[hydraulic tappet|hydraulic lifters]].

===427 (Z11){{Anchor|Z11}}===
A special {{convert|427|CID|L|1|adj=on}} version of the 409 engine was used in the [[Chevrolet Impala#1963|1963 Impala ''Sport Coupé'']], ordered under Chevrolet [[Regular Production Option]] (RPO) Z11.<ref>{{cite web| title=[Chevrolet's] 1963 Z11 427 Impala |url=http://www.348-409.com/z11.html |date=2015 |website=348-409.com |access-date=April 2, 2015}}</ref> This was a special package created for [[Drag racing|drag racers]], as well as [[NASCAR]],<ref>{{cite AV media |last=RK Motors Charlotte |title=132954 / 1963 Chevrolet Impala SS |url=https://www.youtube.com/watch?v=EU-DXTz8ppo |archive-url=https://ghostarchive.org/varchive/youtube/20211222/EU-DXTz8ppo |archive-date=2021-12-22 |url-status=live|date=June 28, 2013 |website=YouTube |access-date=April 7, 2016}}{{cbignore}}</ref> and it consisted of a cowl-induction {{cvt|427|cuin|L|1}} engine and body with selected aluminum stampings. The aluminum body parts were fabricated in [[Flint, Michigan]] at the facility now known as GM Flint Metal Center.<ref>{{cite web |title=GM U.S. Facilities – Flint Metal Center – Plant Summary |url=http://www.gmdynamic.com/company/gmability/environment/plants/facility_db/facility_summary.php?fID=146 |date=2005 |archive-url=https://web.archive.org/web/20061106023649/http://www.gmdynamic.com/company/gmability/environment/plants/facility_db/facility_summary.php?fID=146 |archive-date=November 6, 2006 |url-status=dead |website=GM Global Operations |access-date=April 2, 2015}}</ref> Unlike the later, second-generation 427, it was based on the W-series 409 engine, but with a longer {{cvt|3.65|in|mm|1}} stroke. A high-rise, two-piece aluminum intake manifold and dual Carter AFB carburetors fed a 13.5:1 compression ratio to produce an under-rated SAE gross {{cvt|430|hp|0}} and {{cvt|575|lbft|0}}. Fifty RPO Z11 cars were produced at the [[Flint, Michigan auto industry|Flint GM plant]].

Extant GM Documents show 50 Z11 engines were built at the GM [[Tonawanda Engine]] plant for auto production, and 20 partial engines were made for replacement/over-the-counter use. There is no evidence from GM that shows 57 cars were built.{{clarify|What?|date=October 2014}}{{citation needed|date=October 2014}}