Editing Chevrolet big-block engine (section)

==Mark IV==
The Mark IV differed from the W-series engine in the placement of the valves and the shape of the combustion chambers. The chamber-in-block design of the W-series engine (which caused the power curve to drastically dip above 6500&nbsp;rpm), was replaced by a more conventional wedge chamber in the cylinder head, which was now attached to a conventional 90 degree deck. The valves continued to use the displaced arrangement of the W-series engine, but were also inclined so that they would open away from the combustion chamber and cylinder walls, a design feature made possible by Chevrolet's stud mounted rocker arms. This alteration in valve placement resulted in a significant improvement in [[volumetric efficiency]] at high RPM and a substantial increase in power output at racing speeds. Owing to the appearance of the compound angularity of the valves, the automotive press dubbed the engine the "porcupine" design.<ref>{{cite web|title=Chevy 396-cid V-8 Engine |url=https://auto.howstuffworks.com/chevy-396-cid-v-8-engine.htm |website=How Stuff Works |access-date=29 July 2019|archive-url=https://web.archive.org/web/20190729145355/https://auto.howstuffworks.com/chevy-396-cid-v-8-engine.htm|archive-date=29 July 2019}}</ref>

As part of the head redesign, the spark plugs were relocated so that they entered the combustion chamber at an angle relative to the cylinder centerline, rather than the straight-in relationship of the W-series engine. This too helped high RPM performance. Due to the new spark plug angle, the clearance provided by the distinctive scalloped valve covers of the W-series was no longer needed, and wide, rectangular covers were used.

In all forms (except the aluminum ZL-1), the Mark IV was slightly heavier than the W-series model, with a dry weight of about {{cvt|685|lb|kg}}. Aside from the new cylinder head design and the reversion to a conventional 90 degree cylinder head deck angle, the Mark IV shared many dimensional and mechanical design features with the W-series engine. The cylinder block, although more substantial in all respects, used the same cylinder [[bore spacing]] of {{cvt|4.84|in}} with a larger {{cvt|2.75|in}} main bearing dimension, increased from the {{cvt|2.5|in|1}} of the older engine. Like its predecessor, the Mark IV used crowned pistons, which were [[Casting (metalworking)|castings]] for conventional models and impact extruded ([[forge]]d), solid skirt types in high performance applications.

Also retained from the W-series design were the race-proven Moraine M400 aluminum bearings first used in the 409, and the highly efficient "side oiling" lubrication system, which assured maximum oil flow to the main and connecting rod bearings at all times. Later blocks intended for performance use had the main oil gallery moved up to the cam bearing bore area and provided "priority main" oiling, improving the oil system even further.

===366===
The {{cvt|366|cuin|L|1}} big-block V-8 gasoline engine was used in Chevrolet medium duty trucks and school buses. It had a bore and a stroke of {{cvt|3.935x3.76|in|mm}}. This engine was made from the 1960s until 2004. The 366 used 4 rings on the pistons, as it was designed from the very beginning as a truck engine. The 366 was produced only as a tall-deck engine, with a deck {{cvt|0.4|in|mm}} taller than the 396, 402, and 454 short-deck big-blocks.

===396 and 402<span class="anchor" id="396"></span><span class="anchor" id="402"></span>===
The {{cvt|396|CID|L|1}} V8 was introduced in the [[Chevrolet Corvette (C2)|1965 Corvette]] as the [[Chevrolet L78|L78]] option and in the [[Chevrolet_Chevelle#Z-16_SS_396|Z-16 Chevelle]] as the L37 option. It had a bore × stroke of {{cvt|104x95.5|mm|in|3|order=flip}},<ref>{{cite web |last=McGann |first=John |title=396 Big Block Chevy Stroker Build – Stock-Appearing Stroker 396 |url=http://www.hotrod.com/how-to/engine/ccrp-1010-396-big-block-chevy-stroker-build/ |date=October 1, 2010 |website=Hot Rod Network |access-date=January 20, 2015}}</ref><ref>{{cite web |last=Mann |first=Dave |title=Big block Chevy engines |date=September 26, 2013 |url=http://www.roadsters.com/bbc/ |website=Roadsters.com |access-date=January 20, 2015}}</ref> and produced {{cvt|375|bhp|PS kW|0}} at 5600&nbsp;rpm and {{cvt|415|lbft|Nm|0}} of [[Machine torque|torque]] at 3600&nbsp;rpm.<ref>{{cite web|url=http://www.automobile-catalog.com/car/1969/103730/chevrolet_nova_ss_396_375-hp_4-speed.html|website=automobile-catalog|title=1969 Chevrolet Nova SS 396 375 HP 4-speed|access-date=July 4, 2018}}</ref> The solid lifter version was capable of being operated in the upper 6000&nbsp;rpm range, and when installed in the 1965 Corvette, was factory-rated at {{cvt|425|hp|0}}.

Introduced in 1970, the {{cvt|402|cuin|L|1}} was a {{cvt|396|cuin|L|1}} bored out by {{cvt|0.03|in|mm}}. Despite being {{convert|6|CID|cc}} larger, Chevrolet continued marketing it under the popular "396" label in the smaller cars while at the same time labeling it "Turbo-Jet 400" in the full-size cars.

'''Power rating(s) by year:'''
* [[File:396325hp.jpg|alt=1966 325 hp 396 cubic inch engine|thumb|1966 325 hp 396 cubic inch engine]]1965: {{cvt|325|hp|0}}/{{cvt|375|hp|0}}/{{cvt|425|hp|0}}
* 1966: {{cvt|325|hp|0}}/{{cvt|360|hp|0}}/{{cvt|375|hp|0}}
* 1967: {{cvt|325|hp|0}}/{{cvt|350|hp|0}}/{{cvt|375|hp|0}}
* 1968: {{cvt|325|hp|0}}/{{cvt|350|hp|0}}/{{cvt|375|hp|0}}
* 1969: {{cvt|265|hp|0}}(2bbl)/{{cvt|325|hp|0}}/{{cvt|350|hp|0}}/{{cvt|375|hp|0}}
* 1970: {{cvt|350|hp|0}}/{{cvt|375|hp|0}}
* 1971: {{cvt|300|hp|0}} SAE gross; while SAE net was {{cvt|260|hp|0}} for dual exhaust and {{cvt|206|hp|0}} for single exhaust
* 1972: {{cvt|240|hp|0}} SAE net for dual exhaust and {{cvt|210|hp|0}} SAE net for single exhaust

'''Applications:'''
* 1965 [[Chevrolet Corvette]]
* 1965–1972 [[Chevrolet Chevelle]]
* 1967–1972 [[Chevrolet Camaro]]
* 1968–1970 [[Chevrolet Chevy II / Nova#Third generation (1968–1974)|Chevrolet Nova]]
* 1970–1972 [[Chevrolet Monte Carlo]], [[Chevrolet El Camino]], GMC Sprint, Chevrolet trucks
* 1965–1972 [[Chevrolet Biscayne]], [[Chevrolet Bel Air]], [[Chevrolet Impala]], [[Chevrolet Impala|Chevrolet Impala SS]], [[Chevrolet Caprice]]

'''396 and 402 production codes:'''
:'''396'''
* L-34: produced 1966–69, 10.25:1 compression, Holley ([[Quadrajet|Q-jet]] 1968–1969) carburetor, hydraulic lifters, oval port closed chamber [[cylinder head|head]]s, forged steel crankshaft, and two-bolt main caps. It produced {{cvt|350|to|360|hp|0}}.<ref name="Muscle Cars Magazine p.62">{{cite journal |journal=Guide to Muscle Cars |date=February 1987 |page=62}}</ref>
* L-35: produced 1965–69, 10.25:1 compression, Q-jet carburetor, forged steel (1965–67) or nodular iron (1968–69) crankshaft, hydraulic lifters, oval port closed chamber heads, and two-bolt main caps. It produced {{cvt|325|hp|kW}}.<ref name="Muscle Cars Magazine p.62"/>
* L-37: produced 1965, similar to L-78 except for having hydraulic lifters and slightly milder cam; 2-bolt main caps; designed specifically for the 1965 [[Chevrolet_Chevelle#Z-16_SS_396|Z-16 Chevelle]]
* L-66: produced 1969, rare two-barrel carburetor, 9:1 compression, nodular iron crankshaft, hydraulic lifters, oval port closed chamber heads, and two-bolt main caps. It produced {{cvt|265|hp|0}}.<ref name="Muscle Cars Magazine p.62"/>
* L-78: produced 1965–69, had a [[Holley Performance Products|Holley]] {{cvt|800|cuft/min}} [[carburetor]], [[compression ratio]] 11:1, forged pop-top pistons, aluminum high-rise intake manifold, steel [[crankshaft]], solid lifter cam (same as the L-72), rectangular ("square") port closed chamber heads, and four-bolt main caps. It produced {{cvt|375|bhp|0}} in mid-size cars, {{cvt|425|bhp|0}} in [[Chevrolet Corvette|Corvette]]s.<ref name="Muscle Cars Magazine p.62"/>

:'''402'''
* LS-3: produced 1970–72, 10.25:1 (1970) or 8.5:1 (1971) compression, hydraulic lifters, nodular iron crankshaft, and two-bolt main caps. It produced {{cvt|330|hp|0}} (1970), {{cvt|300|hp|0}} (1971), {{cvt|210|or|240|hp|0}} (1972 net horsepower, single or dual exhaust).<ref name="Muscle Cars Magazine p.62"/>
* L-34: produced 1970. Same as {{cvt|396|cuin|L|1}} L-34 from 1967 to 1969.
* L-78: produced 1970. Same as {{cvt|396|cuin|L|1}} L-78 from 1966 to 1969.

===427===
{| border="0" style="float:right;"
|-
|[[Image:1966 Chevrolet Corvette 427 engine.JPG|thumb|150px|L36 427 in a 1966 [[Chevrolet Corvette]]]]
|-
|[[Image:SC06 1967 Chevrolet Corvette 427 L89 engine.jpg|thumb|150px|L71 427 in a 1967 [[Chevrolet Corvette]]]]
|}
The highly successful and versatile {{cvt|427|cuin|L|1}} version of the Mark IV engine was introduced in 1966 as a production engine option for full-sized Chevrolets and Corvettes. The passenger vehicle 427 should not be confused with the tall deck 427 which was designed for light trucks and busses. The bore was increased to {{cvt|4+1/4|in|mm|0}}, with power ratings varying widely depending on the application. There were smooth running versions with [[hydraulic lifters]] suitable for powering the family [[station wagon]], as well as rough-idling, high-revving solid lifter models usually applied to a minimally equipped, plain-looking, two-door [[Chevrolet Biscayne|Biscayne]] [[sedan (car)|sedan]] fitted with the {{cvt|425|hp|0}} version of the 427 (RPO [[Chevrolet L72|L72]]).

Perhaps the ultimate 427 for street applications was the {{cvt|435|bhp|PS kW|0}} at 5800&nbsp;rpm and {{cvt|460|lbft|Nm|0}} at 4000&nbsp;rpm of torque [[Chevrolet_L72#L71|L71]] version available in 1967 to 1969 Corvettes, and in the Italian [[Iso Grifo]]. This engine was identical to the {{cvt|425|hp|0}} L72 427 (first introduced in 1966), but was fitted with 3×2-barrel [[Holley Performance Products|Holley]] [[carburetor]]s,<ref>{{cite web|url=https://www.carfolio.com/specifications/models/car/?car=44242|website=carfolio|title=1967 Chevrolet Corvette 427 L71, 1968 MY 19400|access-date=July 3, 2018}}</ref> known as "[[Tri-Power]]," in lieu of the L72's single 4-barrel carburetor. Both engines used the same high-lift, long-duration, high-overlap camshaft and large-port, cast-iron heads to maximize cylinder head airflow (and, hence, engine power) at elevated engine-operating speeds. Consequently, the engines offered very similar performance and resulted in a car whose performance was described by one automotive journalist as "the ultimate in sheer neck-snapping overkill". Typical 2000s-era magazine road tests of Corvettes with the engine yielded 0-{{cvt|60|mph|km/h}} in 5.6 seconds and [[Dragstrip|{{convert|1/4|mi|m|0}}]] in 13.8 second at {{cvt|104|mph}} range for both the L72 and L71.<ref>{{cite web|url=https://www.myclassicgarage.com/knowledge-base/1967-Chevrolet-Corvette|archive-url=https://web.archive.org/web/20180704063500/https://www.myclassicgarage.com/knowledge-base/1967-Chevrolet-Corvette|url-status=dead|archive-date=July 4, 2018|website=myclassicgarage|title=1967 Chevrolet Corvette|access-date=July 3, 2018}}</ref><ref>{{cite web|url=https://www.motortrend.com/news/1967-chevrolet-corvette-427-1968-porsche-911l-in-head-2-head/|website=motortrend|title=1967 Chevrolet Corvette 427 vs. 1968 Porsche 911L|date=13 August 2014|access-date=July 3, 2018}}</ref>

In 2011, ''Super Chevy Magazine'' conducted a chassis [[dynamometer]] test of a well documented, production-line, stock but well-tuned L-72 "COPO" Camaro, and recorded a peak {{cvt|287|hp|kW|0}} at the rear wheels, demonstrating the substantial difference between 1960s-era SAE "gross" horsepower ratings and horsepower at the wheels on a chassis dynamometer. Wheel horsepower (which is obtained at the drive wheels and thus takes into account drivetrain power loss of the transmission, driveshaft, and differential, as well as all accessories) does not equate to [[Horsepower#SAE net power|SAE net HP]] (which is horsepower at the flywheel, but with all essential peripherals included (such as the water pump, alternator,  and air cleaner), accessories (such as a power steering pump, if fitted), a stock exhaust system, and all required emission controls, none of which are accounted for in SAE gross, which only measures gross flywheel horsepower).<ref name="superchevy1">{{cite web |last=Hill |first=Patrick |url=http://www.superchevy.com/technical/additionaltech_perfdir/sucp_1102_chevrolet_muscle_car_dyno_wars/viewall.html |title=Chevrolet Muscle Car Dyno Wars |website=Superchevy.com |publisher=Super Chevy Magazine |date=February 1, 2011 |access-date=November 1, 2014}}</ref>

The RPO L89 was an L71 fitted with aluminum heads. While this option produced no power advantage, it did reduce engine (and hence, vehicle) weight by roughly {{convert|75|lb}}.{{cn|date=May 2024}} Although the difference in straight line performance was negligible, the weight savings resulted in superior vehicle weight distribution and improved handling and braking.

====ZL1====
The all-aluminum 1969 ZL1 version of the 427 engine was developed primarily for [[Can-Am]] racing,{{cn|date=May 2024}} which did not require homologation to compete,; it was very successful in cars like the [[McLaren M8A|McLaren M8B]]. The ZL1 specifications were nearly identical to the production L88 version of the 427, but featured an aluminum block in addition to aluminum cylinder heads. The first Corvette with the RPO ZL1 engine package was built in early December 1968 and featured aluminum closed chamber heads shared with the L88. Both L88 and ZL1 optioned cars continued to be built with closed chamber heads until approximately March 1969, when the open combustion chamber aluminum heads finally were in production and began being fitted to the L88 and ZL1 engines. The ZL1 engine also featured a lightweight aluminum water pump, a camshaft that was slightly "hotter" than the L88's, and a specially tuned aluminum intake manifold. Like the L88, the ZL1 required 103 [[Octane rating|octane (RON)]] (minimum) fuel (102 octane RON [Sunoco 260] represented the highest octane gasoline sold at common retail stations), used an unshrouded radiator, and had poor low-speed idle qualities – all of which made the two engines largely unsuitable for street use. 

As impressive as the ZL1 was in its day, actual engine dyno tests of a certified production line stock ZL1 revealed {{cvt|376|hp|kW|0}} SAE net with rated output swelling to {{cvt|524|hp|kW|0}} [[Horsepower#SAE gross power|SAE gross]] with the help of optimal carb and ignition tuning, open long tube racing headers, and with no power-sapping engine accessories or air cleaner in place.<ref name=CRG-COPO427>{{cite web |last1=Glowacki |first1=Bill |title=COPO 427: The Relentless Pursuit of Acceleration |url=http://www.camaros.org/copo.shtml |department=CRG Research Report |year=2014 |publisher=Camaro Research Group |access-date=November 1, 2014|display-authors=etal}}</ref>  A second engine dyno test conducted on a second production line stock (but recently rebuilt and partially blueprinted) ZL1 revealed nearly identical figures for the various "gross" conditions.<ref>{{cite magazine |title=Chevy 427 Dyno Results |url=http://members.cox.net/harddrivin1le/ZL1DYNOTEST.JPG |archive-url = https://web.archive.org/web/20111112211831/http://members.cox.net/harddrivin1le/ZL1DYNOTEST.JPG | archive-date = 2011-11-12 | pages=20–24|magazine = Musclecar Enthusiast |url-status=dead }}</ref>

Period magazine tests of the ZL1 were quite rare due to the rarity of the engine itself. ''High-Performance Cars'' tested a production line stock, but well tuned, example and recorded a 13.1 second/{{cvt|110|mph}} {{convert|1/4|mi|m|0}}, which correlates quite well with the previously referenced {{cvt|376|hp|kW|0}} SAE Net figure. ''Super Stock and Drag Racing Magazine'' recorded an 11.62 second/{{cvt|122.15|mph}} {{convert|1/4|mi|m|0}} in a professionally tuned ZL1 Camaro with open long-tube S&S equal-length headers, drag slicks, and minor suspension modifications, driven by drag racing legend Dick Harrell{{Citation needed|date=April 2025}}. Using Patrick Hale's Power/Speed formula, the {{cvt|122.15|mph}} trap speed indicated low 11-second ET (elapsed time) potential (e.g. with larger drag slicks) and suggested something on the order of {{cvt|495|hp|kW|0}}, "as installed", in that modified configuration{{Citation needed|date=April 2025}}. This large difference in power suggests that the [[Original equipment manufacturer|OEM]] exhaust manifolds and exhaust system were highly restrictive in the ZL1 application, as was also the case with the similar L88.

The then-staggering $4,718 cost of the ZL1 option doubled the price of the 1969 Corvette, resulting in just two production Corvettes (factory option at dealer) and 69 of the 1969 Camaros (non-dealer option from factory – COPO 9560) being built with the ZL1.

Chevrolet capitalized on the versatility of the 427 design by producing a wide variety of high-performance, "over-the-counter" engine components as well as ready-to-race [[Automobile engine replacement|"replacement" engines]] in shipping crates. Some of the components were developed to enhance the engine's reliability during high RPM operation, possibly justifying the use of the description "heavy duty." However, most of these items were racing parts originally designed for Can-Am competition that found their way onto dealers' shelves, and were meant to boost the engine's power output.

Beginning in 1969, the highest performance 427 models were fitted with the new open (vs. closed) chamber cylinder heads, along with design improvements in crankshafts, connecting rods, and pistons, adopted from the Can-Am development program.

Chevrolet gave all 427 engines except the ZL1 a torque rating of {{cvt|460|lbft|0}}.

==== Mark IV 427 performance specifications ====
{| class="wikitable"
|-
!First<br />Year
!Last<br />Year
!Engine<br />Code
!Features
!Compression<br />ratio
!Factory<br />Gross Power<br />Rating
|-
|1966||1969|| L36 || 4-barrel || 10.25:1 || {{cvt|390|hp|kW|0}}
|-
|1966||1969|| L72 || 4-barrel + solid-lifters, more aggressive cam and high flow cylinder heads||  |11.00:1 || {{cvt|425|hp|kW|0}}{{efn|Chevrolet actually advertised this engine as {{cvt|450|hp|kW|0}} for a short period of time. There is speculation over whether this engine actually put out {{cvt|450|hp|kW|0}} gross, or if this was a marketing oversight that was later corrected.{{cn|date=May 2024}}}}
|-
|1967||1969|| L68 || L36 with 3×2-barrel carbs. ||  10.25:1 || {{cvt|400|hp|kW|0}}
|-
|1967||1969|| L71 || L72 with 3×2 barrel carbs.||  11.00:1 || {{cvt|435|hp|kW|0}}
|-
|1967||1969|| L89 || L71 + aluminum  heads; RPO L89 also applied to L78 "375 HP" 396 engine with aluminum head option. || 11.00:1 || {{cvt|435|hp|kW|0}}
|-
|1967||1969|| L88 || Racing-spec cam, high-flow aluminum heads (casting #s varied by model year) and some upgraded, competition-grade parts || 12.50:1{{efn|L88 had a 12.5:1 compression ratio with closed chamber heads except during the last half of 1969, when it had open chambered heads that yielded 12.0:1{{cn|date=May 2024}}}} || {{cvt|430|hp|kW|0}}{{efn|L88 was rated for {{cvt|430|hp|0}} at 5200&nbsp;rpm.}}
|-
|1969||1969|| ZL1 || Aluminum block with open chamber "3946074" aluminum heads (the early Corvette RPO engine featured a closed chamber head); cam even "hotter" than L88's; upgraded parts similar to L88's || 12.00:1 || {{cvt|430|hp|kW|0}}
|}
'''Applications:'''
* 1966–1969 [[Chevrolet Biscayne]]
* 1966–1969 [[Chevrolet Caprice]]
* 1966–1969 [[Chevrolet Impala]]
* 1966–1969 [[Chevrolet Corvette]]
* 1968–1969 [[Chevrolet Camaro]] (most were dealer installed, but in 1969 both the L-72 and the ZL-1 were factory options)

'''427 production codes:'''
* LS-1: produced 1969, 10.25:1 compression, Q-jet carburetor, oval port closed chamber heads, hydraulic lifters, nodular iron crankshaft, and two-bolt main caps. It produced {{cvt|335|hp|kW|0}}.<ref name="Muscle Cars Magazine p.63">{{cite journal |journal=Guide to Muscle Cars |date=February 1987 |page=63}}</ref>
* L-36: produced 1966–69, 10.25:1 compression, Holley or Q-jet carburetor, nodular iron crankshaft, hydraulic lifters, oval port closed chamber heads, and two-bolt main caps. It produced {{cvt|385|hp|kW|0}} in 1967–68 full-size cars, {{cvt|390|hp|kW|0}} in 1969 full-size cars and Corvettes (by exhaust system).<ref name="Muscle Cars Magazine p.63"/>
* L-68: produced 1967–69, 10.25:1 compression, [[Pontiac V8 engine#347|Tri-Power]], nodular iron crankshaft, hydraulic lifters, aluminum oval port closed chamber heads, and two-bolt main caps. It produced {{cvt|400|hp|kW|0}}, and was used in Corvettes.<ref name="Muscle Cars Magazine p.63"/>

===454===
[[File:2014 Rolling Sculpture Car Show 47 (1970 Chevrolet Chevelle SS 454 engine).jpg|thumb|454 in a 1970 Chevelle SS]]

For 1970, the big-block was expanded again, to {{cvt|454|cuin|L|1}}, with a [[Bore (engine)|bore]] × [[Stroke (engine)|stroke]] of {{cvt|4+1/4|x|4|in|mm|1}}. The 1970 [[Chevrolet Corvette]] LS-5 version of this engine was factory-rated at {{cvt|390|bhp|PS kW|0}} and {{cvt|500|lbft|Nm|0}}, and the LS-6 engine equipped with a single 4-barrel {{cvt|800|cuft/min}} [[Holley Performance Products|Holley]] [[carburetor]] was upgraded to {{cvt|450|bhp|PS kW|0}} at 5600&nbsp;rpm and {{cvt|500|lbft|Nm|0}} at 3600&nbsp;rpm of [[Machine torque|torque]].<ref>{{cite web|url=https://www.supercars.net/blog/1964→1972-chevrolet-chevelle-ss454/|website=supercars.net|title=1964→1972 Chevrolet Chevelle SS 454|access-date=July 5, 2018|editor=Nick D. |date=March 29, 2016}}</ref><ref>{{cite web|url=https://heacockclassic.com/articles/the-best-muscle-car-1970-ls-6-chevelle/|website=heacockclassic.com|title=The 1970 LS-6 Chevelle Was America's King Of The Streets|access-date=July 5, 2018|editor=Paul Zazarine |date=November 14, 2014}}</ref>

The AHRA ASA (Showroom Stock Automatic) Class record-holding Chevelle LS-6 for the 1970 racing season posted a best-of-season trap speed of {{cvt|106.76|mi/h|km/h|0}},<ref name=Chevelle454>{{cite web |title=1970 Chevelle 454 LS-6 |url=http://www.chevelle454ls6.com/1970_chevelle_454_ls6.htm |access-date=November 1, 2014}}</ref> which suggests something on the order of 350 "as installed" (SAE Net) HP for a {{convert|3900|lb|0}} car-and-driver combination.{{citation needed|date=October 2021}} Indeed, ''Super Chevy Magazine'' conducted a chassis dyno test of a well-documented, well tuned, but stock 1970 LS-6 Chevelle and recorded 283 peak HP at the wheels<ref name="superchevy1" /> – a figure that lines up quite well with the previously referenced 350 SAE Net HP figure.{{citation needed|date=October 2021}}

An even more powerful version of the 454, producing {{cvt|465|hp|kW|0}} and {{cvt|610|lbft|0}}, was dubbed the LS-7 (not to be confused with the modern, mid 2000s, 7-litre [[Chevrolet Corvette]] engine that powered the [[Chevrolet Corvette C6|C6]] Z06, which is an LS7). Several LS-7 intake manifolds were individually produced and sold to the general public by a few Chevrolet dealers as optional performance parts. The LS-7 was later offered as a [[Automobile engine replacement|crate engine]] from Chevrolet Performance with an officially rated power minimum of {{cvt|500|hp|0}} gross.

In 1971, the LS-5 produced {{cvt|365|hp|0}} and {{cvt|550|lbft|0}}, and the LS-6 option came in at {{cvt|425|hp|0}} and {{cvt|575|lbft|0}}. In 1972, only the LS-5 remained, when SAE net power ratings and the move towards emission compliance resulted in a temporary output decline, due to lowered compression, to about {{cvt|270|hp|0}} and {{cvt|468|lbft|0}}. The 1973 LS-4 produced {{cvt|275|hp|kW}} and {{cvt|468|lbft|N.m}}, with {{cvt|5|hp|0}} and {{cvt|10|lbft|0}} gone the following year. Hardened valve seats further increased reliability and helped allow these engines to last much longer than the earlier versions, even without the protection previously provided by [[Tetraethyllead|leaded fuel]]. 1974 was the last year of the 454 in the Corvette, although the Chevelle offered it in the first half of the 1975 model year. It was also available in the full size Impala/Caprice through model year 1976.
* 1970–1976 [[Chevrolet Caprice]]
* 1970–1975 [[Chevrolet Chevelle#1970 Chevrolet Chevelle|Chevrolet Chevelle]]
* 1970–1975 [[Chevrolet Monte Carlo]]
* 1970–1975 [[Chevrolet El Camino]]
* 1971–1975 [[GMC Sprint]]
* 1970–1974 [[Chevrolet Corvette]]

===L19===
General Motors introduced EFI in 1987, which was found on GM C1500 SS, C/K2500, and C/K3500 trucks. The 454 EFI version was rated from {{cvt|230|hp|0}} to {{cvt|255|hp|0}} and from {{cvt|385|lbft|0}} to {{cvt|405|lbft|0}} of torque. The 1991–1993 454SS made 255 horsepower at 4000&nbsp;rpm and 405 lb-ft of torque at 2400&nbsp;rpm thanks to dual 2.5" catalytic converters. All other versions, including the 1990 SS, made 230 horsepower at 3600&nbsp;rpm and 385 lb-ft of torque at 1600&nbsp;rpm through a single 3" catalytic converter. 
* 1987–1990 Chevrolet R2500 and R/V3500
* 1985–1990 [[Chevrolet C/K]]
* 1989–1990 [[Chevrolet van|Chevrolet/GMC 3500 van]]

===Commercial applications===
Mark IV engines saw extensive application in Chevrolet and GMC medium duty trucks, as well as in [[Blue Bird Corporation]]'s [[Blue Bird All American|All American]] and [[TC/2000]] transit buses (the latter up until 1995, using a 427 with purpose-built carburetor). In addition to the 427, a {{cvt|366|cuin|L|1}} version was produced for the commercial market. Both the 366 and 427 commercial versions were built with a raised-deck, four-bolt main bearing cap cylinder to accommodate an extra oil control ring on the pistons. Unfortunately, the raised deck design complicated the use of the block in racing applications, as standard intake manifolds required spacers for proper fit. Distributors with adjustable collars that allowed adjustments to the length of the distributor shaft also had to be used with 366 and 427 truck blocks. These engines can be modified for performance use with different length rods, pistons, and/or crank throws, but it's typically deemed easier and more cost effective to use readily available 454 and 502 displacement standard blocks for performance use.

Mark IV engines also found themselves widely used in power boats. Many of these engines were ordinary Chevrolet production models that were fitted with the necessary accessories and drive system to adapt them to marine propulsion. [[Mercury Marine]], in particular, was a major user of the Mark IV in marine drives, and relabeled the engines with their corporate logo.