AMC V-8s

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The AMC V8 has a [http://www.crankshaftcoalition.com/wiki/Talk:AMC_V-8s storied] history. Read about the pros and cons of both AMC V8 engines. This article will touch on the highlights. Enjoy!

{{Note1}} Portions of the following text came from [http://www.wps.com/AMC/Rambler-327/The%20New%20American%20Motors%20V-8%20Engine%20%28SAE%20Paper%20details%29.htm The New American Motors V-8 Engine] by John F. Adamson, Carl E. Burke and David B. Potter of the American Motors Corp. This paper was first presented at the SAE National Passenger-Car, Body and Materials Meeting, Detroit, Michigan, March 7, 1956.  

AMC made their own V-8 engines. The company did use a few parts from other manufacturers, namely transmissions, carburetors, and electrical systems (distributor, alternator/generator, starter, etc.). Many people see a similar displacement (327, 390, etc.) engine with a Delco (GM) or Autolite (Ford) ignition/starting/charging system on it and assume the engine was purchased from GM or Ford. Anyone familiar with GM and Ford V-8s would immediately know they were looking at a different engine at first glance though.  

==The Packard connection leading to the Gen 1 production AMC V8==

AMC only purchased one V-8 from another manufacturer. That was the Packard 320 cid V-8 for the big 1955-'56 Nash Ambassador and Hudson Hornet models. These were equipped only with the Packard Ultramatic auto trans. AMC and Packard were supposed to have had a "gentleman's agreement" to cross purchase parts. This was partially to establish a working relationship between the two companies for a possible future merger. As it turned out, Packard felt it was doing AMC a favor by selling AMC V-8s. Packard sent a few bids in to AMC, but they were rejected for being too high- even though AMC was paying a premium for the Packard V-8s.  

Needless to say, this incensed AMC management. George Mason, head of AMC, ordered his engineers to get him a V-8 as soon as possible. Just 18 months after receiving the order, AMC introduced a 250 cid V-8 in mid 1956. It was only used in the Nash Ambassador Special and Hudson Hornet Special. The Specials were really two door Statesman/Wasp models with Ambassador/Hornet trim. The Statesman/Wasp bodies were built on a shorter wheelbase and lighter than the bigger cars. Using that platform helped the little 250 out.  

18 months from drawing board to production doesn't sound all that short today, but in the era of slide rules and drafting boards (no computer modeling or even calculators!) it was phenomenal. One of the ways the AMC Engineering Department worked this miracle was to hire David Potter from Kaiser-Frazer. He had previously worked with Continental Engines (owned by Kaiser Industries) on a V-8 intended for the Kaiser-Frazer line, however Kaiser had since purchased Willys-Overland resulting in a change of it's priorities; from making cars, to making the more popular Jeeps. AMC literature reports that "The entire program was under the direction of Meade F. Moore, Vice-President of Automotive Research and Engineering, and through his efforts the project was carried on cooperatively by our Kenosha and Detroit Engineering Departments. Obviously, such a division of both design and development required the utmost in teamwork by F. F. Kishline, Chief Engineer, and his assistants, E. L. Monson and J. S. Voigt in Kenosha, and by R. H. Isbrandt, Chief Design Engineer, and W. S. Berry, Chief Mechanical Engineer, in Detroit." AMC concluded in their announcement of the new engine saying "In short, our objective was an engine with maximum flexibility with regard to future displacement requirements without sacrificing any of the performance features of the power-plant. Economy of operation and manufacturing processes, along with excellent weight and durability characteristics, were all part of our aims. We think that we have succeeded in reaching these objectives, and have produced an engine that is second to none. It is an engine of which we are justly proud."

The new for '56 640 lb. Rambler V8 (fully assembled 'long block') was lighter at that time than all other US V8 engines, except for the '55 Chevrolet 'small block'. And when speaking about their intake and exhaust port designs, AMC reported that "the theoretical gas velocity through the valve is lower than that of any automotive engine on the market today." & "Exceptionally close liaison was maintained with our manufacturing personnel during the design and development stages of the engine. As a result, many economies in fabricating and tooling processes were built into the original design and have since been carried through into production.

Of particular interest is the cylinder-block boring equipment, which has been designed to finish simultaneously blocks of two different bore dimensions. It contains two sets of roughing, finishing, and chamfering tools, and blocks of either bore size can enter the equipment in any mixed sequence. Each station is set to tool one size bore, and when a block enters that station, a probe automatically determines whether or not to cycle the cutting heads."...

Wherefore it may be said that not only was the Rambler V8 'state-of-the-art', AMC set a new standard of excellence for the US industry.

The Rambler V8 design features a visually identical 'Hudson X' crankcase gallery, having the main bearing webbing form an 'X' around the main bearings transferring load from the the crankshaft into the block with extreme stiffness and minimized vibration for maximum durability. The Rambler V8 shaft mounted rocker arm assemblies are visually identical to the the former Nash inline six cylinder engines. The engine features an excellent oil system, which is perhaps the best oil system of any US V8 ever made and serves as a model of oil system design theory for it's attributes.

All 250 models use solid lifters, the 287/327s are hydraulic. These engines were also used by Grey Marine for boats in the late '50's and early to mid '60's. All the marine engines used solid lifters regardless of size.

The AMC Rambler V8 is only recently been labeled 'Gen 1' by newer AMC enthusiasts. This labeling was first used by AMC writer Frank Swygert (editor/forum member 'farna') in an effort to place the engine where it technically "should" be. Tehcnically the labelling is correct -- this is the first generation of AMC V-8s, AMC having been formed in May of 1954 and V-8 engine development starting in 1955. The 66-69 second generation models and 70-91 third generation models are very similar, but having a different block and head casting led to the labelling of Gen-2 and Gen-3. "Series" could have been used instead of "Generation", but "Generation" (shortened to "Gen") seemed to be the most correct description. Previously the first generation AMC V-8 had been (and still is) referred to as either the "Nash V-8" or "Rambler V-8". It was used in both Nash and Rambler branded, as well as AMC branded cars ("Rambler" was dropped from the 65 Marlin and 66 Ambassador, those being branded as AMC models). Technically it was built by the American Motors Corporation, not Nash or Rambler.

'Gen-1', 'Gen-2', etc. labeling ideas were first used by Chevrolet small block V-8 enthusiasts to distinguish the differences among that group of very similar engines. This has apparently led many to believe the terms were "borrowed" from the GM engine family or that a GM enthusiast created the labels. There was a small effort to distnguish between GM and AMC labels -- GM models are typically labeled with all capitals (GEN-1, GEN-2, etc. -- sometimes with no dash), whereas Frank used a single capital (Gen-1 -- and always a dash). The label was used becasue it was technically correct and fit -- GM's labelling wasn't even considered until others pointed out the similarities and made the assumption that the labeling was "borrowed".

==The Gen 2 V8==

By the mid '60's the heavy Gen-1 V-8 was becoming dated. AMC engineers didn't rest once the Gen-1 was introduced though. They had been working on a thoroughly modern light weight V-8 to replace the Gen-1. The Gen-2 engine was introduced in mid year 1966 as a 290cid V8. The only thing it shares with the Gen-1 is the bore spacing. This was done so that existing boring tooling could still be used. Everything else about the Gen-2 was totally unique and new, even the bell housing bolt pattern was changed. These engines are similar to a small block, but have a larger bore spacing similar to a big block. Many people call them a "mid block", but it's just the AMC Gen-2 V-8 -- AMC only made one V-8 design at any given time.

The 290 and 343 used cast cranks and rods. The 390 was intended for high performance and was made with a forged crank and forged rods. AMC stated that the primary reason forgings were used was to get the engine to market quicker -- they didn't have time to thoroughly test cast components and still introduce the engine when they desired to. As a result, the AMC Gen-2 390 has a tougher bottom end than any similar displacement Mopar, Ford or Chevy. Reworked AMC 390 rods are good to 7000+ rpm, whereas the other makes require replacement performance rods. A lot of work also went into development of the head. AMC heads were some of the best flowing heads on the market at the time. A typical AMC head flowed as good or better than other makes' high performance heads.  

AMC made some improvements in the Gen-2 design for 1970, thus becoming the Gen 3. This resulted in different block and head castings and slightly larger displacement. The only change to the block was adding approximately 1/16" to the deck height and increasing the stroke accordingly.

The Gen 1 to Gen 2 block deck height difference was 1/32" nominal, or 0.033". Gen 1 was 9.175" nominal block deck height and Gen 2 was 9.208" nominal block deck height per the Performance American Style booklet AMC printed in the early '70's.

The 290 became a 304, 343 a 360, and the 390 a 401 (with a little added stroke in the crank than the 390). The 401 wasn't introduced until 1971. The 390 was kept for 1970 only by using a special piston -- the pin height was altered to keep displacement at 390 inches. The head casting was changed to create a slightly larger "dog leg" exhaust port (Gen-2 heads have rectangular exhaust ports) to improve exhaust flow.  

The AMC V-8 finally went out of production when Chrysler halted Jeep Grand Wagoneer production at the end of the 1991 model year. This makes the 360 by far the most numerous AMC V-8. It can easily be built to produce over 400 hp on pump gas. It's as modern as any other make V-8 of the time, and has as much potential. There isn't as large a selection of performance parts, but the parts still available are the ones known to work well -- not a lot of junk to wade through. The parts cost a little more than the more common small block Ford and Chevy parts, but no more than any other make. Cost to build is partially offset by the very good heads. Until the Vortec L31 5.7L head was introduced, Chevy heads weren't any better than AMC heads. Now, Edelbrock has aluminum heads for the 343, 360, 390 and 401 AMC engines.