AMC V8 engine

American Motors produced a series of widely-used V8 engines before being absorbed into Chrysler. Some continued well after the merger in Jeeps.

GEN-1 Nash/Hudson/Rambler V-8s (1956-1966)

Many members of the AMC hobby refer to this engine family as the "GEN-1" AMC V-8. It was created almost by accident. AMC President George W. Mason had a verbal agreement with Packard that the two companies would supply parts for each other when practical. AMC started buying Packard V-8s in 1954 for the 1955 Nash and Hudson big cars. These were supplied with Packard "Ultramatic" automatic transmissions - exclusively. Packard sent AMC some parts bids, but rejected them all as too expensive. An incensed George Mason ordered his engineering department to develop an in-house V-8 as soon as possible. The engineering department hired David Potter, a former Kaiser engineer, to come in and help develop the engine. Potter had previously worked on a V-8 design for Kaiser, and had the experience necessary to take the engine from drawing board to full production in just under 18 months, an engineering feat in itself.

All these engines share common external dimensions, weight (about 640 pounds), and forged crankshaft and rods. Displacement varied by bore alone since it was cheaper to cast different blocks than to forge multiple crankshafts (forged cranks and rods were used in all engines until the early sixties when casting technology caught up to required strength in such parts). The 250 has a 3.50" bore, 287 3.75", and the 327 a 4.0" bore. Bore size is cast on the top of the block near the back of the right bank cylinder head.

250

AMC's first V-8, the 250, was used in American Motors Corporation automobiles from 1956 through 1961. As the name implies, it had 250 in³ (4.1 L) of displacement and was a modern (for the time) OHV/pushrod engine design and made its debut in the Nash Ambassador and Hudson Hornet "Specials" of 1956. These cars had the top of the line model trim, but were built on the shorter wheelbase (Statesman and Wasp) models (hence the "Special" name). The 250 used solid lifters and came in two and four barrel carburetor varieties (4V only in Nash/Hudson "Specials").

All 1958-60 V-8 Ramblers were called "Rebel" (not to be confused with the 1957 Special Edition Rebel). In 1961 The Rambler Six was renamed the Rambler Classic to avoid model confusion in the Rambler line-up. A V-8 then became an option in the Classic instead of a separate model.

287

In mid model year 1963, AMC introduced a 287 in³ (4.7 L) V8. When the 250 was dropped in 1961, there was no V-8 option for Rambler models other than the top of the line Ambassador. Dealers complained, so the 287 was introduced as an option for the "mid size" Rambler. Like the 327, it used hydraulic valve lifters. Only 2V models were produced, there were no 4V options from the factory as this was the economy model V-8. The 287 was produced through 1966.

327

The AMC 327 was similar to the 287, but displaced 327 in³ (5.4 L) due to the bore increase to 4.0". Unlike the 250, the 327 came with hydraulic valve lifters.

This engine debutted in a special edition Rambler Rebel of which only 1500 were made. All had silver paint with a gold annodized "spear" down each side. This was to be the first electronic fuel injected production engine, but teething problems with the Bendix "Electrojector" unit meant that only a few engineering and press cars were built, estimated to be no more than six units, but at least two were known to have been built. One was sent to Daytona Beach for "Speed Week". It was the second fastest car on the beach, bested only by a 57 Corvette with mechanical fuel injection, and only by a couple tenths of a second. The EFI 327 was rated at 288 hp, the production 4V carbureted model at 255 hp. All the EFI cars were reportedly converted to 4V carb before being sold — none are known to have existed outside the engineering department at AMC. The main problem was that vacuum tube and early transistor electronics just couldn't keep up with the demands of "on the fly" engine controls.

The 327 was not available in any other Rambler models in 1957, just the Special Edition Rebel. The Ambassador and Hornet "Special" cars were dropped after 1956, replaced by standard wheelbase models with the 327 instead of 250 V-8. When the big Nash and Hudson cars were dropped they were replaced by the 1958 "Ambassador by Rambler" — a stretched Rebel (Rambler V-8) with the 327 V-8 instead of the 250. The 327 was exclusive to the Ambassador line, and couldn't be ordered in a Rebel or Classic.

GEN-2 AMC Short-Deck V-8 (1966–1970)

The new-generation AMC V8 was first introduced in 1966. It is sometimes referred to as the "GEN-2" AMC V-8. All three engine sizes (290, 343, and 390) share the same basic block design — the different displacements are achieved through various bore and stroke combinations. All blocks share the same external measurements and thus can be swapped easily. Contrary to a popular myth, the AMC V8 was not built by Ford or anyone else. They did share some electrical parts (starter and distributor) with Fords, and some models used Motorcraft (Ford) carburetors, but the engine design is totally different. Bore center measurement was kept the same as the GEN-1 AMC V-8 so that boring equipment could be reused. Other than that, this engine is vastly different from the GEN-1 model. The GEN-1 engine is physically the size of a big-block Ford or GM engine, and is sometimes called a "big-block". The GEN-2 is closer to the physical size of US made small-block V-8s except for the bore centers, which are the same as some big-block engines. There are no shared parts between the AMC GEN-1 and GEN-2/3 engines.

The GEN-2 AMC V-8 was first introduced at 290 in³ (4.8 L) in 1966. It was used exclusively in the American model the first year (some reports indicate a few late production Classics had 290s substituted for 287s, but that hasn't been substantiated). The 343 in³ (5.6 L) came out in 1967 and the AMX 390 in³ (6.4 L) arrived in 1968. These engine blocks were unchanged through 1969.

The head used during this time are the so-called rectangle port, named after their exhaust port shape. The 290 heads use smaller valves, 1.787 in (45.4 mm) intake and 1.406 in (35.7 mm) exhaust, in order to prevent problems with the small bore. The 343 and AMX 390 used the same larger valve heads, 2.025 in (51.4 mm) intake and 1.625 in (41.3 mm) exhaust.

290

The base 290 in³ (4.8 L) 290 produced 200 to 225 hp (149 to 168 kW) with a 2V and 4V carburetor, respectively. It was built from 1966 through 1969. It has a 3.75 in. bore (95.25 mm) and 3.28 in. (83.31 mm) stroke.

343

The 343 in³ (5.6 L/5622 cc) 343 has a 4.08 in. (103.6 mm) bore and 3.28 in. (83.31 mm) stroke. The basic 343/2V produced 235 hp (175 kW) and was built from 1967 through 1969. Output for the optional 4V carburetor version was 280 hp (209 kW) and 365 ft·lbff (495 N·m) gross. This version had a 10.2:1 compression ratio.

AMX 390

In addition to the largest bore and stroke, the 390 in³ (6.4 L) AMX 390 motor also got heavier main bearing support webbing and a forged steel crankshaft and connecting rods. Forged cranks and rods were used for known strength — there was inadequate time for testing cast parts for durability without slipping AMCs desired introduction schedule. Once forging dies were made it wasn't cost effective to test cast parts due to the relatively low number of engines produced. This was continued with the 401. The bonus was that the big AMC engines never had rod breaking problems when used for performance, unlike other US companies' large displacement small block engines. The GEN-2 AMX 390 produced 315 hp (235 kW) and was built in 1968 and 1969. Bore is 4.165 in. (105.791 mm) and stroke is 3.68 in. (93.47 mm). Maximum factory recommended overbore is only 0.020", though they are commonly bored 0.030".

GEN-3 AMC Tall-deck (1970-1991)

In 1970, all three blocks grew in deck height and gained a new head design. These changes made this the third generation of AMC V-8, hence it is sometimes referred to as the GEN-3 AMC V-8. The stroke and deck height on the 290 and 343 was increased by 0.16" (~5/32"), becoming the 304 and 360, respectively. The AMX 390 remained at the same displacement by using a special 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, which was discontinued after 1970. In 1971 the 390 was stroked by 0.16" 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 66-69 rectangle port heads and are thus the best for performance. There are two reasons for the flow increase: First, the area of the port is larger, due to the dog leg. Second, 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. The intakes can be interchanged by slotting the bolt holes, but the added deck height of the GEN-3 engine means that sealing and port match will be compromised. GEN-3 intakes can be machined to fit GEN-2 engines by surface grinding the intake flanges (by a machine shop) and slotting the center holes.

There is a persistent myth about 1970-mid 1971 "319" or "291" AMC heads. These heads have the dog-leg exhaust ports and 50-52 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 US 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 early heads are not "the best" AMC heads as many have come to believe. They will raise compression on a later engine with no other changes, but if building an engine get the proper pistons for the desired ratio. There is no reason to search out these relatively hard to find, and more expensive when found, heads for performance.

304

The 304 in³ (5.0 L) produced 210 hp (157 kW) in 1970-71 and was built starting in 1970. Later models produced less power from the factory, going down yearly. 1972-78 models were rated at 150 hp. It was rated at 130 hp in 1979, the last year it were installed in passenger cars, and 125 hp in 1980-81, the last years it was used in Jeep vehicles.

360

The AMC 360 in³ (5.9 L) 360 2-barrel produced 235 to 245 hp (175 to 183 kW) in 1970 to early 71 while the 4-barrel produced 285 to 295 hp, 175 to 220 hp from mid 71-75, 140-180 hp in 1976, 129 hp in 1977, and 140 hp from 1978-91. It was the last AMC V-8 to be manufactured. It was used exclusively in Jeep Wagoneer models from 1972-84, Cherokee from 1974 to 1983, and Grand Wagoneer from 84 to 91.

390

The AMC 390 in³ (6.4 L) 390 produced 325 hp (242 kW) in all except the Rebel Machine, which produced 340 hp (254 kW) due to a different intake. Production only lasted one year before it was stroked to become the 401. Like its GEN-2 cousin, the maximum factory recommended overbore is only 0.020", though they are commonly bored 0.030".

401

The 401 in³ (6.6 L) 401 produced 330 hp (246 kW) gross in 1971 and 255 hp (190 kW) net 1972-75. In 1976 it was rated at 315 hp. It was last produced in 1979. It was used exclusively in full size Jeeps 1977-79. Like the 390, the 401's crankshaft and connecting rods are forged steel. Like the 390, factory recommended overbore is only 0.020", commonly bored to 0.030".

"Service Replacement" Multi-Displacement Block

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. It was also sold as a heavy duty racing block, which is speculated to be the real reason it was produced in the first place. It appeared in 1970 in time for the 1971 Trans-Am racing season. 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" Javelins built to homolgate the "duck tail" spoiler. Those received standard 360 or 401 engines.

AMC V8 hp/Torque, Compression & Bore/Stroke by year

Notice that from 1972 & up the hp/Torque figures are 'net' rating:

1966 287-2B 198 hp@? ?ft·lbf@? ?.?:1 ?.?*?.? 327-2B 250 hp@? ?ft·lbf@? ?.?:1 ?.?*?.? 327-4B 270 hp@? ?ft·lbf@? ?.?:1 ?.?*?.? 1967 290-2B 200 hp@4700 285 ft·lbf@2800 8.7:1 3.750*3.280 290-4B 225 hp@4800 300 ft·lbf@3200 10.0:1 3.750*3.280 343-2B 235 hp@4400 345 ft·lbf@2600 8.7:1 4.080*3.280 343-4B 280 hp@4800 365 ft·lbf@3000 10.2:1 4.080*3.280 1968 290-2B 200 hp@4600 285 ft·lbf@2800 9.0:1 3.750*3.280 290-4B 225 hp@4700 300 ft·lbf@3200 10.0:1 3.750*3.280 343-2B 235 hp@4400 345 ft·lbf@2600 9.0:1 4.080*3.280 343-4B 280 hp@4800 365 ft·lbf@3000 10.2:1 4.080*3.280 390-4B 315 hp@4600 425 ft·lbf@3200 10.2:1 4.165*3.574 1969 290-2B 200 hp@4600 285 ft·lbf@2800 9.0:1 3.750*3.280 290-4B 225 hp@4700 300 ft·lbf@3200 10.0:1 3.750*3.280 343-2B 235 hp@4400 345 ft·lbf@2600 9.0:1 4.080*3.280 343-4B 280 hp@4800 365 ft·lbf@3000 10.2:1 4.080*3.280 390-4B 315 hp@4600 425 ft·lbf@3200 10.2:1 4.165*3.574 390-4B(AMX) 340 hp@4800 430 ft·lbf@3400 12.2:1 4.165*3.574 1970 304-2B 210 hp@4400 305 ft·lbf@2800 9.0:1 3.750*3.440 360-2B 245 hp@4400 365 ft·lbf@2600 8.5:1 4.080*3.440 360-4B(Early) 290 hp@4800 390 ft·lbf@3000 10.2:1 4.080*3.440 360-4B(Late) 295 hp@4800 395 ft·lbf@3000 10.5:1 4.080*3.440 390-4B 335 hp@5000 420 ft·lbf@3200 10.2:1 4.165*3.574 390-4B(Machine) 340 hp@5000 427 ft·lbf@3600 10.2:1 4.165*3.574 1971 304-2B 210 hp@4400 300 ft·lbf@2600 8.4:1 3.750*3.440 360-2B 245 hp@4400 365 ft·lbf@2600 8.5:1 4.080*3.440 360-4B(Early) 295 hp@4800 395 ft·lbf@3000 10.5:1 4.080*3.440 360-4B(Late) 285 hp@4800 385 ft·lbf@3000 9.5:1 4.080*3.440 401-4B(Early) 335 hp@5000 435 ft·lbf@3400 10.2:1 4.165*3.680 401-4B(Late) 330 hp@5000 430 ft·lbf@3400 9.5:1 4.165*3.680 1972 304-2B 150 hp@4200 245 ft·lbf@2500 8.4:1 3.750*3.440 360-2B 170 hp@4000 285 ft·lbf@2400 8.25:1 4.080*3.440 360-4B 195 hp@4400 295 ft·lbf@2900 8.25:1 4.080*3.440 360-4B(Dual Ex) 220 hp@4400 315 ft·lbf@3100 8.25:1 4.080*3.440 401-4B 235 hp@4600 ?ft·lbf@? 8.25:1 4.165*3.680 401-4B(Dual Ex) 255 hp@4600 345 ft·lbf@3300 8.25:1 4.165*3.680 1973 304-2B 150 hp@4200 245 ft·lbf@2500 8.4:1 3.750*3.440 360-2B 170 hp@4000 285 ft·lbf@2400 8.25:1 4.080*3.440 360-4B 195 hp@4400 295 ft·lbf@2900 8.25:1 4.080*3.440 360-4B(Dual Ex) 220 hp@4400 315 ft·lbf@3100 8.25:1 4.080*3.440 401-4B 235 hp@4600 ?ft·lbf@? 8.25:1 4.165*3.680 401-4B(Dual Ex) 255 hp@4600 345 ft·lbf@3300 8.25:1 4.165*3.680 1974 304-2B 150 hp@4200 245 ft·lbf@2500 8.4:1 3.750*3.440 360-2B 170 hp@4000 285 ft·lbf@2400 8.25:1 4.080*3.440 360-4B 195 hp@4400 295 ft·lbf@2900 8.25:1 4.080*3.440 360-4B(Dual Ex) 220 hp@4400 315 ft·lbf@3100 8.25:1 4.080*3.440 401-4B 235 hp@4600 ?ft·lbf@? 8.25:1 4.165*3.680 401-4B(Dual Ex) 255 hp@4600 345 ft·lbf@3300 8.25:1 4.165*3.680 1975 304-2B 150 hp@4200 245 ft·lbf@2500 8.4:1 3.750*3.440 360-2B 175 hp@4000 285 ft·lbf@2400 8.25:1 4.080*3.440 360-4B 195 hp@4400 295 ft·lbf@2900 8.25:1 4.080*3.440 360-4B(Dual Ex) 220 hp@4400 315 ft·lbf@3100 8.25:1 4.080*3.440 401-4B 255 hp@4600 345 ft·lbf@3300 8.25:1 4.165*3.680 1976 304-2B 120 hp@3200 220 ft·lbf@2200 8.4:1 3.750*3.440 360-2B 140 hp@4000 260 ft·lbf@2400 8.25:1 4.080*3.440 360-4B 180 hp@4400 280 ft·lbf@2800 8.25:1 4.080*3.440 401-4B 215 hp@4200 320 ft·lbf@2800 8.25:1 4.165*3.680 1977 304-2B 121 hp@3450 219 ft·lbf@2000 8.4:1 3.750*3.440 360-2B 129 hp@3700 245 ft·lbf@1600 8.25:1 4.080*3.440 360-4B ?hp@? ?ft·lbf@? 8.25:1 4.080*3.440 401-4B ?hp@? ?ft·lbf@? 8.25:1 4.165*3.680 1978 304-2B 130 hp@3200 238 ft·lbf@2000 8.4:1 3.750*3.440 360-2B 140 hp@3350 278 ft·lbf@2000 8.25:1 4.080*3.440 360-4B ?hp@? ?ft·lbf@? 8.25:1 4.080*3.440 401-4B ?hp@? ?ft·lbf@? 8.25:1 4.165*3.680 1979 304-2B 125 hp@3200 220 ft·lbf@2400 8.4:1 3.750*3.440 360-2B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 360-4B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 401-4B ?hp@? ?ft·lbf@? ?.0:1 4.165*3.680 1980 304-2B 125 hp@3200 220 ft·lbf@2400 8.4:1 3.750*3.440 360-2B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 360-4B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 1981 304-2B 125 hp@3200 220 ft·lbf@2400 8.4:1 3.750*3.440 360-2B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 360-4B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 1982 360-2B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 360-4B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 —- 1991 360-2B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440 360-4B ?hp@? ?ft·lbf@? ?.?:1 4.080*3.440

The list is compiled from "Perfomance American Style" (mainly), "American Cars 1946-1975" and various old manuals, TSM's, road tests and pamphlets

... as you can see, the list far from complete, please contribute

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