Editing AMC V8 engine (section)

== Gen-3 AMC tall-deck (1970–1991)<span class="anchor" id="3"></span><span class="anchor" id="1970"></span> ==
[[File:1970 AMC Javelin 390 V8 RamAir engine bay.jpg|thumb|right|Engine bay of a 1970 [[AMC Javelin|Javelin]] with a Ram Air 390 V8]]

In 1970, all three blocks grew in deck height and gained a new head design. Although the engine is an outgrowth of the Gen-2 V8, these changes cause it to be regarded as the third generation of AMC V8, or "Gen-3". The stroke and deck height on the 290 and 343 were increased by {{cvt|0.16|in|mm|2}} on both engines, becoming the {{cvt|304|CID|L|1}} and {{cvt|360|CID|L|1}}, respectively. The 1970 AMX 390 remained at the same displacement by using a special connecting rod and piston for this year only. It is believed that AMC kept the 390 this last year due to the reputation it had garnered in the two-seater AMX, then still in production. (It was discontinued after 1970). In 1971 the 390 was also stroked by the same {{cvt|0.16|in|mm|2}} as the other two versions of the engine to become the 401.

The other change in 1970 was the switch to the "dog-leg" heads. These heads flow 20% better on the exhaust side than the 1966-1969 rectangular port heads and are thus the best for performance. There are two reasons for the flow increase: (1) the area of the port is larger, due to the dog leg and (2) the shape of the port floor was changed from a concave to a convex curve. The concave floor tended to bend the exhaust flow upwards which caused turbulence when the flow was forced to go down into the exhaust manifolds. By switching to a convex floor the curvature of the flow starts in the head and proceeds much more smoothly into the exhaust manifold resulting in less turbulence and better flow.

The center two intake bolts on each head were relocated to prevent accidental mix-ups of Gen-2 and Gen-3 intakes.

AMC heads 319 and 291 used between 1970-mid 1971 have the dog-leg exhaust ports and 50-52&nbsp;cc combustion chambers. They are commonly identified by the first three (319) or last three (291 for the 360-401 heads; 304 used a different casting) digits of the casting number. There was a U.S. auto industry-wide shift to lower compression ratios in mid-1971, so AMC increased combustion chamber size to 58-59 cc. The first three digits of the casting number on the large chamber heads are 321, 322, or 323 depending on year. The only difference between small and large chamber Gen-3 heads is the combustion chamber size.

The advertised power drop from the 1971 ratings to the ones for the 1972 model years (for example, the 1971 304 produced 210&nbsp;hp and the 1972 304 was 150&nbsp;hp) is not due to any engine changes, but an industry-wide shift from SAE Gross (also known as "brake horsepower" or "bhp") to SAE Net power ratings. The 1971 and 1972 engines produce the same power.<ref name="Peters-98">{{cite book |last=Peters |first=Eric |title=Road Hogs: Detroit's Big, Beautiful Luxury Performance Cars of the 1960s and 1970s |year=2011 |publisher=Motorbooks |isbn=978-0-7603-3764-6 |page=98 |url= https://books.google.com/books?id=LKh7qgJ8hT8C&pg=PA98}}</ref> The 1971 and earlier versions were rated using "gross" horsepower, which is with the engines operating with no accessories or [[Belt (mechanical)|drive belts]], air filters, nor any exhaust system restrictions. The change to the more realistic "net" horsepower ratings for 1972 and later required the engine to be driving all stock factory accessories and to use the factory air filter system and a simulated factory exhaust. Power is measured at the flywheel for both systems. For example, even with the modifications to reduce emissions and increase efficiency, AMC's {{cvt|401|CID|L|1}} engine was among the strongest factory-spec engines available in an American car in 1971, with more horsepower than [[Pontiac (automobile)|Pontiac]]'s standard {{cvt|455|CID|L|1}} and [[Chevrolet]]'s {{cvt|454|CID|L|1}} that powered the Corvette.<ref name="Peters-98"/>

=== 304 ===
[[File:1970 AMC Javelin 304 base model badge.jpg|thumb|right|1970 emblem]]

The 304 has a displacement of {{cvt|304|CID|L|1}}, which produced {{cvt|210|hp|kW PS|0}}(gross rating) in 1970-71 and was built starting in 1970.<ref name="amcenginesA">{{cite web |url= http://www.matadorcoupe.com/images/engineappchart.jpg |title=Engine application chart |publisher=matadorcoupe.com |access-date=20 August 2014}}</ref> Output declined yearly thereafter, initially due a shift from SAE Gross to SAE Net horsepower. 1972-75 models were rated at {{cvt|150|hp|kW PS|0}} (net rating from 1972 onwards). It was rated at {{cvt|130.5|hp|kW PS|0}} in 1978, and {{cvt|125|hp|kW PS|0}} in 1979, the last year it was installed in passenger cars, and in 1980–81, the last years it was used in Jeep vehicles. The [[International Harvester Corporation]] {{convert|304|CID|L|1|adj=on}} SV "Comanche" V8 engines are sometimes mistaken for the AMC 304, however, the IHC V8 engine family has no relation to the AMC V8 and was in fact first produced in 1959, 11 years prior to the AMC designed 304. The similarity in displacement is purely a coincidence.

=== 360 ===
[[File:1974 Bricklin 4 speed white at Potomac Ramblers meeting 05.jpg|thumb|right|The AMC 360 V8 was standard in the 1974 [[Bricklin SV-1]] sports car]]

The AMC 360 has a displacement of {{cvt|5896.1|cc|CID|2|disp=flip}}.<ref name="amcenginesA"/> The 2-barrel produced {{cvt|235|hp|kW PS|0}} to {{cvt|245|hp|kW PS|0}} in 1970 to early 1971 while the 4-barrel produced {{cvt|285|hp|kW PS|0}} to {{cvt|295|hp|kW PS|0}}, {{cvt|175|hp|kW PS|0}} to {{cvt|220|hp|kW PS|0}} from mid-1971 through 1975, {{cvt|140|hp|kW PS|0}} to {{cvt|180|hp|kW PS|0}} in 1976, {{cvt|129|hp|kW PS|0}} in 1977, and {{cvt|160|hp|kW PS|0}} from 1978 through 1991.<ref>{{cite book|url= https://books.google.com/books?id=eT7LT69STO0C&pg=PA232 |pages=232–233 |title=Ultimate American V-8 Engine Data Book |edition=Second |first=Peter C. |last=Sessler |publisher=Motorbooks International |year=2010 |isbn=978-0-7603-3681-6}}</ref>

This engine was used in the 1970 AMX as the base engine and also in the 1970 [[AMC Rebel|Rebel]], the 1971 through 1978 [[AMC Matador|Matador]], [[Jeep Gladiator (SJ)|Jeep J-series]] trucks from 1970 until 1987, [[Jeep Wagoneer (SJ)|Wagoneer (SJ)]] models from 1972 until 1984, [[Jeep Cherokee (SJ)|Cherokee (SJ)]] from 1974 until 1983, as well as in the full-sized Grand Wagoneer from 1984 through 1991 - becoming one of the last carbureted engines used in an American-built vehicle.<ref>{{cite web |last1=Perkins |first1=Chris |title=The Jeep Grand Wagoneer Was One of the Last Carbureted Cars Sold New in the US |url= https://www.roadandtrack.com/car-culture/classic-cars/a27005762/1991-jeep-grand-wagoneer-review/ |work=Road & Track |date=1 April 2019 |access-date=3 January 2023}}</ref> The 360 V8 was also installed in the [[Bricklin SV-1]] sports car for the 1974 model year.<ref>{{cite news |last1=Zyla |first1=Greg |title=Cars We Remember column: Re-visiting the Bricklin SV1: Malcolm Bricklin's past and present legendary efforts |url= https://www.providencejournal.com/story/special/2020/10/12/cars-we-remember-column-re-visiting-bricklin-sv1-malcolm-bricklins-past-and-present-legendary-effort/42746265/ |work=The Providence Journal |date=12 October 2020 |access-date=3 January 2023}}</ref>

The 360 was the last AMC V8 to be manufactured. It continued to be produced after Chrysler bought American Motors in 1987 as the standard engine in the Jeep Grand Wagoneer through 1991, with the only modification being the "360" casting replaced with "5.9L" on the side of the block.<ref>[https://books.google.com/books?id=eT7LT69STO0C&pg=PA228&dq=360-cid+engine+until+1991+in+the+Jeep+Grand+Wagoneer Sessler, p. 228.]</ref>

=== 390 ===
The {{cvt|390|CID|L|1}} AMC V8 produced {{cvt|325|hp|PS kW|0}} and {{cvt|420|lbft|Nm kgm|0}} of [[torque]] in all except the [[AMC Rebel#The Machine|Rebel Machine]]. This [[muscle car]] engine was rated at {{cvt|340|hp|PS kW|0}} and {{cvt|430|lbft|Nm kgm|0}} of [[torque]] due to a different intake. Production only lasted one year (1970) before it was stroked to become the {{cvt|401|CID|L|1}}.

=== 401 ===
[[File:Amc401v8-1.jpg|thumb|right|1974 AMC 401]]

The {{cvt|401.11|CID|cc|1}}<ref name="amcenginesA"/> produced {{cvt|330|hp|PS kW|0}} gross in 1971 and {{cvt|255|hp|PS kW|0}} net from 1972 through 1975. In 1976 it was rated at {{cvt|215|hp|PS kW|0}}. Like the 390, the 401's crankshaft and connecting rods are forged steel. It was last produced in 1978.

The 401 was available in the Javelin, Matador, and Ambassador car lines and in Jeeps from its introduction in 1971 through 1974. In 1975 and 1976, emission controls, insurance rates, and high gasoline prices meant the 401 was available on the large Matador model, and then only for police department orders. Buyers of full-sized Jeeps (Wagoneer, Cherokee, J-10, and J-20) could order a 401 until 1978 (not available in 1979<ref>{{Cite web|url= http://www.lov2xlr8.no/brochures/jeep/79jp/79jp.html|title = Lov2xlr8.no}}</ref>). This engine was also supplied to International Harvester for use as an optional engine in International's [[International Harvester Light Line pickup|Light Line pickup]] trucks and [[International Harvester Travelall|Travelalls]] from late 1973 through 1974 where it was designated 'V-400' to differentiate it from IHC's own V/LV series 401.

=== "Service replacement" blocks ===
There was also a "Service Replacement" block made as a modified GEN-3 design. This is a 401 casting (same casting number) without the displacement cast into the side and with a 360 bore and thicker deck. In theory, this single block could be built as any 343-401 GEN-2 or GEN-3 engine. A dealer could stock one or two blocks to use for warranty replacement.

The main bearing web area was thicker in the 390, 401, and SR blocks, thick enough that two additional bearing cap bolt holes could be drilled and tapped for an aftermarket four-bolt main cap, providing a stronger bottom end. AMC never built a factory four-bolt main block, they sold aftermarket four-bolt main caps through their Group 19 performance parts program.

The SR block was also sold as a heavy-duty racing block. It appeared in 1970 in time for the 1971 Trans-Am racing season and was used in the factory Trans-Am backed cars prepared by TRACO for Penske Racing, with Mark Donohue the primary driver. Since it was a standard factory part it did not have to be homologated under T/A rules, and ''was not'' used in the 2501 "Mark Donohue" [[AMC Javelin|Javelins]] built to homologate the "ducktail" spoiler. Those received standard 360 or 390 engines, buyers' choice.