Editing AMC V-8s

This is just  quick page to get started. I'll add more info as questions come in and I get time. Rather than edit the page, I would prefer anyone make corrections or ask questions in discussion.

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 real familiar with GM and FORD V-8s would immediately know they were looking at a different engine at first glance though. 



AMC only purchased one V-8 from another manufacturer. That was the Packard 320 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 ot 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 rejected them all as 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 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. used to help 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 way the AMC Engineering Department worked this miracle was to hire a Mr. Potter from Kaiser-Frazer. He had worked with Continental Engines (owned by Kaiser Industries) on a V-8 intended for the Kaiser-Frazer line, but those weren't doing well enough to justify the cost. Prototypes had already been made though. So AMC "bought" an engineer who already had intimate V-8 design knowledge. The engine was built rather heavy also. It wasn't state-of-the-art for the time, just typical. No time to make a "dream engine", just had to get a basic, reliable V-8 in production. This is the "Gen-1" AMC V-8, also referred to as the"Nash V-8" or "Rambler V-8". AMC was formed in 1954 by the merger of Nash and Hudson, so anything designed from scratch after 54 is technically an AMC design. 

There were three sizes of AMC Gen-1 V-8s:
1956-61 250
1957-66 327
1963-66 287
All shared the same external dimensions and forged crank and rods (same stroke). The main difference was in the bre. The 250 used a 3.50" bore, the 287 a 3.75" bore and the 327 a 4.00" bore. There were of course three different block castings. It is rumored that early 287 blocks can be bored out to 4.00", but i advise having the block sonic checked before boring. All three of these heavy cast blocks are thick and will easily take an 0.125" over bore, but that is usually pushing the limit. 

All three engines can share the same components except for pistons. All 250 models use solid lifters, the 287/327 are hydraulic. These engines were used by Grey Marine for boats in the late 50s and early to mid 60s. All the marine engines used solid lifters as well, regardless of size.



By the mid 60s 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 eventually replace the Gen-1. The Gen-2 engine was introduced in mid year 1966 as a 290. 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 an 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 Gen-2 came in three sizes also:
1966-69 290
1967-69 343
1968-69 390
The 290 and 343 used cast cranks and rods. The 390 was always 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 intro the engine when they desired to. As a result, the AMC Gen-1 390 doesn't have the problem of breaking rods at high rpm that the big three small block 400s have. Worked over 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. 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 290 became a 304, 343 a 360, and the 390 a 401 (with a little extra 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. 

So there were four Gen-3 sizes:
1970-79 304
1970-91 360
1970 only 390
1971-79 401



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 make 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 -- nit 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. The typical SBC or SBF really needs better aftermarket or now hard to find performance head to be equal to the AMC V-8 heads.