Brief History

AMC came into being with the merger of the Nash-Kelvinator Corporation and Hudson Motor Car Company on May 1,1954. It came to an end in August of 1988 when the remaining shareholders agreed to exchange their AMC stock for Chrysler stock, making AMC a wholly owned subsidiary of Chrysler. Chrysler dropped the AMC name and called the new division Eagle/Jeep. The Eagle half of the division was dropped after a few years, leaving Jeep.

AMC had a history spanning 91 years. The first Rambler was built by Thomas B. Jeffery and his son Charles in 1897. This was an experimental model. Three years later Thomas Jeffery bought a plant in Kenosha, WI, and formed the Thomas B. Jeffery Company. The first Rambler (the name chosen for the company's car, which incidentally was the name of a bicycle manufactured by the Gormully & Jeffery Bicycle Company of Chicago -- Thomas Jeffery was a partner until 1900) was put up for public sale in March 1902. 1500 Model C and Model D Ramblers were sold that year, making it the SECOND car to be mass produced in the U.S., one year behind Oldsmobile and one year ahead of Ford. The C and D were the same car -- the D had a folding top and side curtains whereas the C was open.

Thomas Jeffery died March 21, 1910. The company was incorporated under Wisconsin law on 15 June of the same year. In 1914 the Thomas B. Jeffery Co., Inc., renamed the car line "Jeffery" in honor of the late founder. Charles Jeffery survived the sinking of the Lusitania, a luxury liner torpedoed in 1915 by the Germans. This brought the US into World War I and got Charles to thinking there was more to life than building cars. He decided to retire from the auto business and put the successful company up for sale. It was bought on August 16, 1916 by Charles W. Nash. Nash left his position as President of General Motors Corp. to head his own company. Autos started wearing the Nash badge in 1917.

Myths

A lot of myths have been formed about the number four US auto maker. The most persistent is that they used parts from other makers and just made bodies of their own. That isn't entirely true. AMC did use some parts from other makers, but less than 15% in any given year. What AMC learned to do was use what resources they had very wisely. If purchasing a part from an outside contractor was more cost efficient than developing their own and didn't take away from the unique character of the company's products that's what they did. In this they were actually way ahead of the other manufacturers! Today most manufacturers, even the largest like GM and Ford, subcontract many of their parts and assemblies to other companies. Like other manufacturers, AMC owned in whole or had an interest in many smaller companies that produced parts for them and other auto makers. AMC bought the following major parts from other major auto companies:

Steering columns (Saginaw, 1966-up)
Steering boxes (Saginaw, 1960-up manual, 1965-up power)
Carburetors (all years, mix of Carter and Holley, Motorcraft added in 1970)
Ignition Systems (all years, mix of Delco and Autolite points, 1975-77 Chrysler
BID electronic, 78-88 Motorcraft electronic)
Charging and Starting Systems (all years, mix of Delco and Autolite)

Other parts such as belts, hoses, tires, batteries, etc. have been purchased from outside sources by all manufacturers for many years. AMC has always made their own engines with only a few exceptions, and always built their own bodies.

Four Cylinder Engines

This is the department AMC was always lacking in. They should have developed a four themselves long before they eventually did. Instead they found themselves in quite a predicament when the first gas shortages of the seventies hit the US auto industry very hard.

Because of the time required to develop a reliable engine, AMC first attempted to buy a design they could build themselves. Volkswagen/Audi had such an engine, the 2.0L Audi Fox model. VW was getting ready to discontinue the Fox and was willing to sell a license to produce the engine and eventually sell the tooling to AMC also. From 1977 to 1979 AMC assembled 2.0L engines from major castings imported from Germany with some parts made in the US. AMC machined all parts and assembled the engines at a plant in Richmond, Indiana. Unfortunately AMC didn't use fuel injection or electronic ignition with the little engines, and the Gremlin was much heavier than the Fox. This same engine was used later in the Porsche 944 with fuel injection and electronic ignition, but was very "high strung" -- it required high rpm to produce much power and would have been just as unsuited for something as heavy as the Gremlin and Spirit. In AMCs defense, they intended to produce a smaller, lighter car that would be more suitable to that engine, but they were unable to afford development. The smaller car eventually came in the form of the Renault Alliance.

The little 2.0L four was barely adequate for the Gremlin and Spirit with a four speed transmission. Even those felt under powered with an auto trans. Add air conditioning and power accessories and it got worse. Even so the 2.0 was offered in the larger Concord (sedan only, not wagons) 1978. It wasn't used in 79 Concords and few equipped 78s (I've only seen one in a salvage yard, none running). AMC dropped the little engine after 1979 because of dismal sales over the three year period it was produced.

Until AMC could get a four cylinder of their own into production they bought GM 2.5L "Iron Duke" engines. This engine had just enough more torque than the little 2.0L to make a difference. They were used in cars and Jeep vehicles through 1983. AMC only used them for the three year period 1980-83.

The new, downsized Jeep Cherokee XJ was introduced in 1984 along with the new Jeep 2.5L four cylinder engine. Because it shares the same size with the previously used GM four it is often confused with it. The Jeep four was created by cutting the two center cylinders out of a 258 six block. A single piece rear main seal was designed instead of the 258 two piece seal and the GM 2.5L bell housing pattern was used. This saved AMC some money as they were already casting bell housings for the GM four and having Chrysler make 904 automatic transmissions with the GM four bell pattern. An entirely new head was designed for the new engine. A carburetor was used for the first year, with throttle body fuel injection added in 1985 and direct port injection in 1991. This engine was adopted by Dodge to replace the 2.2L as the base engine of the Dakota mid-size truck around 1990. The only AMC passenger car to receive this engine was the 1984 Eagle 4WD. The last 2WD AMC passenger car was built in 1983 and the four was dropped from the Eagle line after 1984.

A serial number or Engine Day Build Code (see) is stamped on the engine block on a machined pad. 2.0L (121) OHC engines have the pad located on the left rear corner of the block near the bell housing. 2.5L models have the pad on the right side just to the rear of the distributor between cylinder #3 and #4. This does not apply to the GM 2.5L engine.

The oldest six cylinder is the 195.6 family (see 195.6 FAQ, http://home.att.net/ ~farna/AIM.html), produced from 1940 through 1965. A new six, the 232, was introduced in 1964. This was a seven main bearing six, probably the strongest available at the time is was introduced. Ford, Chevy, and Chrysler sixes of the time still used four main bearings, though Ford and Chrysler would introduce seven main bearing in-line sixes shortly after. A shorter stroke version, the 199, was introduced in 1965 as a replacement for the aging 195.6. In 1971 the deck height of the six cylinder block was increased by 1/8". The extra stroke allowed creation of a 258 cubic inch engine with a new crank and rod. The 199 was dropped after 1970, making the 232 the smallest six. The 232 was dropped after 1979, leaving AMC with the 258 as its only six cylinder engine. In 1986 the 258 was reworked into the 242 (4.0L) for use in the Jeep XJ and MJ (downsized Cherokee and Comanche pickup) lines. Bore was increased from 3.75" (common to all 199/232/258 engines) to 3.875", but the stroke was reduced from the 258's 3.90" to 3.41". This allowed quicker spin up while retaining adequate displacement. A new head design derived from the AMC 2.5L four (see "Four cylinder Engines", below) was used for the 242. The 242 also used direct port fuel injection and electronic ignition. These were developed with help from then partner Renault.

A GM 2.8L V6 was purchased for the XJ Cherokee until the 4.0L six was ready (1984 and 1985). This was a carbureted engine. Jeep marketing planners felt that a six cylinder engine was needed to help sales. It is believed that the 2.8L was chosen because it shared the same bell housing pattern and transmissions as the 2.5L Jeep four (see above). This would reduce the cost of using the engine as any other would require tooling for a new automatic bell housing or an adapter, or purchasing transmissions from an additional source. Another model transmission would mean additional service costs and headaches as well (since Jeep had used the 2.5L GM four they were already equipped with diagnostic tools for the similar emission controls of the 2.8). The 2.8L could use the same drivetrain as the 2.5L four. This saved money, but in reality the diminutive V6 put out little more power than the four. V6 model Cherokees are routinely avoided now. A later model fuel injected four, even the first TBI models, puts out as much horse power and nearly as much torque as the V6. The Jeep four is also a more durable engine.

Complicating matters is the fact that GM had trouble with the rear main seal of 1984 and earlier 2.8 V6s. The 85 models solved this with a new seal. A 3.1L or 3.4L V6 will bolt in place of a 2.8L but most of those were made for front wheel drive applications. These would require custom engine mounts. GM did make a service replacement 3.1L block with mounting points for front and rear drive vehicles. Some early 3.1 equipped cars have been found to have these blocks, so check 1991-92 models. Note that the 3.1/3.4 is a different block than the earlier 3.0/3.3. I do not know if these earlier engines will bolt in. GM dropped them after only a few years, however, due to problems. They were replaced by the 3.1/3.4 models. Simply replacing the carburetor on a 2.8L equipped Jeep with fuel injection from a later model GM would be a vast improvement and the most economical upgrade (from 115 hp to 135 hp from GM "A" body, plus better economy and driveability).

The old Nash 252.6 OHV engine was used through 1956 in Nash models only. The old Hudson L-head sixes were still produced for the Nash bodied Hudsons of 1955-57. All 57 Nash and Hudson models received the GEN-1 327 V8.

A serial number or Engine Day Build Code (see) is stamped on the engine block on a machined pad. Early six cylinders have the pad located on the front left side of the block. Later models have the pad on the right side just to the front of the distributor between cylinder #2 and #3. Different codes are used for each size engine. Codes vary with years. This does not apply to the GM 2.8L V6 engine.

The first V8 AMC used was the Packard 320. Packard's "Ultramatic" automatic transmission was the only trans available with this engine. It was used only in 1955 and some 1956 models. AMC had talked with Packard in the late 40s about possible merger. AMC officials still hoped this would happen and felt a cooperative venture would strengthen bonds between the two companies and pave the way. AMC and Packard agreed to use each other as parts suppliers -- or so AMC thought. In reality Packard president James Nance felt he was doing AMC a favor by selling them engines and felt no obligations to purchase from them (Packard was still a healthy company in 1955) . A few bids were sent over just for show, but were rejected as being to high. This took place early in the hand-shake agreement.

This incensed AMC president George Mason so much that he ordered his engineers to develop a V8 engine as soon as possible (the hand-shakle agreement was meant to foment trust between the two companies -- we see how that worked!). In order to do this AMC hired former Kaiser engineer Dave Potter. He had already worked on V8 designs at Kaiser and was able to have an engine ready for installation in a vehicle in less than 18 months!

In order to meet the short development time the engine couldn't be cutting edge technology. Instead it used all proven design and build techniques. It was on a par with other V8s of the time, but not the then new, cutting edge Chevrolet small block (also introduced in 1955). In other words the engine was relatively bulky and heavy for its displacement, but very strong. There wasn't time to build and test cast rods and crankshafts so forged parts were used. With the bulk of the block and forged crank and rods, this proved to be an exceptionally strong engine. Today a few racers have discovered this and are using them for high boost turbocharging. The only thing required is custom forged pistons -- the crank and rods are as strong or stronger than aftermarket performance parts after a little preparation.

The only drawback to the design was the heads. They used conventional vertical overhead valves. With the valve going straight down into the head there was limited room -- the valves could only be so big before shrouding affected flow. The block was capable of supporting over 400 cubic inches, but the heads would need to be redesigned to support large enough valves. Only slightly larger valves can be installed in these heads, and it may not be worth the cost. The turbo racers mentioned earlier overcome valve size somewhat with boost -- up to 23 psi -- but limit displacement to near stock, only boring to take out wear.

Note that Chevrolet didn't make their small block 327 until 1962. The early AMC V8 more closely resembles the Chevrolet 396 big block, though there are very notable differences. This is as close to a "big block" as AMC ever made.

AMC engineers knew that the heavy V8 couldn't compete with more modern small blocks introduced by the competition (Chevy in 55, Chrysler 55, Ford 63). The heavy engines weren't in line with AMC's economy image either, though they were very much responsible for the Rambler's reliability and smoothness reputations.

AMC started development on a new V8 shortly after the first was in full production. The new engine, introduced in mid 1966, shared some features of modern small blocks and others more common with big block of the era. It had wide bore centers comparable to a big block. This made the block a little longer but provided plenty of room for future growth and increased stability. For this reason some publications call it a "mid block". It had a Buick style oil pump made into the timing cover. The distributor was driven off the camshaft via a gear that bolts to the front of the camshaft. The oil pump drive shaft was slotted to fit a tang on the end of the distributor shaft.

A 390 cubic inch performance model was introduced for the 1968 AMX. This used the same dimensions as the 290 and 343 but had thicker main bearing webs for added stiffness in that area. AMC never produced a factory four bolt main bearing engine as they felt the two bolt cap was adequate, but they did cast the webs thick enough to be drilled for aftermarket four bolt main caps for racing purposes. To keep high reliability with the longer stroke all 390 and larger AMC engines used forged crankshafts and rods. According to AMC engineers forgings were originally used due to inadequate time to test cast parts. AMC decided to keep the forgings, either due to low numbers of the engines or to retain high reliability. In either case an AMC 390/401 is much stronger than comparable small block 400 engines. No aftermarket cranks or rods are required for racing, just careful preparation of the stock parts.

Displacements were increased in 1970 by lengthening the deck height of the block by 0.16" for that much longer stroke. The 390 had built such a performance reputation that a new rod was made to keep a 390 for 1970. The stroke was changed only 0.11" for the big engine to bring displacement to 401 cubic inches for 1971. It was felt that more than 400 inches would be larger than needed. Even then the block had to be notched at the bottom of the bores to clear the crankshaft counterweights. The higher deck height meant a slightly wider intake was necessary.

The heads were also changed in 1970. 1966-1969 heads have rectangular exhaust ports. 1970 and later heads have a "dog leg" or "pork chop" shaped exhaust port, sort
of like this:     __
                      |   |__
                      |___ |

The larger port increased exhaust flow by around 30%, making AMC heads the best flowing production heads available. For this reason the Chrysler "Magnum" V8 head was based on the AMC design. The new ports also required new exhaust manifolds.

AMC V8 engines are generally classified as GEN-1, GEN-2, and GEN-3 (GEN for generation). The GEN-1 engine is the large 1955-66 250-327 block, GEN-2 the smaller 1966-69 290/343/390, and GEN-3 the taller 304/360/401 (and 1970 390) model. Although the GEN-2 and GEN-3 share essentially the same block except for the 0.16" deck height increase, the head, intake manifold, and exhaust manifold changes justify the separate designation. GEN-3 engines also use 1/2" head bolts, GEN-2 uses 7/16" head bolts. Heads will interchange between the two as long as the bolt size is accounted for. Step dowels are made to fit the better flowing GEN-3 heads on GEN-2 blocks, but for racing purposes it is better to drill and tap the older block for 1/2" head bolts. To put GEN-2 heads on a GEN-3 block the bolt holes must be reamed to fit 1/2" bolts.

Technically AMC didn't build a small block or big block, they just made one V8 engine with the exception of the short overlap in 1966. In reality the engines are compared with the competition. With this in mind the GEN-1 can be considered a "big block" because of its external dimensions and weight, and the GEN-2 and GEN-3 small blocks for the same reasons. Some publications have mistakenly called the 390 and 401 "big blocks" because of the displacements. Externally all GEN-2 and GEN-3 engines are the same size with the exception of height and width. All bolt patterns and external bolt on parts (except intake and exhaust manifolds) are identical. All internal parts interchange, though crankshaft and rod swaps may require custom pistons. GEN-1 parts are unique to that engine.

There is a myth perpetuated by several magazine articles in the early 90s about the seemingly magic "319" heads for GEN-3 engines. The casting number for these is 3196291, hence the "319" designation. These heads use 50.60cc combustion chambers (commonly rounded to 51cc) for 10:1 compression. In mid 1971 AMC, like all other US auto makers, dropped compression to no more than 9.5:1 (8.0-8.5:1 on average). AMC did this by using a 57.92cc combustion chamber (commonly rounded to 58cc) and adjusting the recesses in the tops of pistons. Because of the magazine articles the 1970-early 71 only 50.60cc heads have become increasingly pricey. They are also unneeded unless one is restoring a 1970 vehicle and wants/needs everything factory correct.

All 1970 and later AMC heads use the same port design. All 360, 390, and 401 heads are identical. These use 2.025" intake and 1.680" exhaust valves (early 70 used a 1.625" exhaust valve) and have the high flow "dog leg" exhaust ports. If building an AMC race engine simply order pistons for the desired compression ratio and forget the smaller chamber heads -- it won't cost any more (maybe less!) if the pistons need replacing anyway. 1970-early 71 304 heads use a different casting (3199517) but are essentially the same as the 360/390/401 heads. Ports may be slightly smaller and castings a bit thinner, but according to all AMC technical data 2.02"/1.62" valves can be installed. Combustion chamber volume for the 304 head is 52.20cc and produced a compression ratio of 9.0:1 with stock pistons. Later 304 heads have a 58.92cc chamber and produce 8.4:1 compression.

The bore size of GEN-1 engines is cast into the left rear of the block. This is covered by the bell housing when engine is in a vehicle with transmission installed. The cubic inch size of all GEN-2 and GEN-3 engines is cast into each side of the block just behind the engine mount plates in the center of the engine. An exception is the 1970 thick cast 360 (used in Donohue Javelins to homologate the thick wall 360 block for Trans-Am racing) and some service replacement engines. Since the Engine Day Build Code or serial number (see Engine Day Build Codes) is located on a removeable tag this is the only reliable way to identify engine size. This does not apply to the Packard V8 engine.