This article is a brief summary of all of Nash's major engine introductions, focusing on major engine designs, upgrades and trends with the goal of illustrating the points in Nash history when major leaps in engine technology occurred. There were many upgrades made during the years of a basic engine design such as a change in bore or stroke which are not considered major design changes and hence are not mentioned. Any corrections or additional information would be welcomed.
When Charlie Nash left General Motors to establish Nash Motors, several key people, especially from the Buick division, came with him to Kenosha, Wisconsin. Nash offered a great opportunity to his engineers to draw and design a brand new, up to the minute technology auto, scheduled to debut in 1918.
Not surprisingly, the engine was quite Buick like, being one of the few overhead valve (OHV) engines on the market at the time. OHV was and is a more efficient engine, but costs more to build. The extra cost is why most other manufacturers did not have overhead valves; the valve in block (commonly called a flathead) was more economical to build. Charlie used this new OHV six cylinder engine as one of the many ways he introduced the best-for-the-money middle class car on the market. Nash did not start off small, with a four, and then progress to a six later.
This original OHV engine was a six cylinder, with state of the art technology; one piece casting for the engine block, three main bearings, dipper rods, but no pressure oiling up to the rocker arms. This first Nash engine was quite plain and clean looking, being devoid of much of anything on either side of the engine. These Nashes were equipped with a bracket on the fire wall to hold an oil can. The owner was responsible for removing the valve cover and oiling the rocker arms and ends of the push rods every 100 miles or so. (I'm not sure what year pressurized oil was delivered to the rocker arms, but I think it was by 1925.) This sounds crude, but Chevrolet, one of the few other OHVs of the day, did not even have a cover to keep dirt from the valve train! Even the notably more expensive air-cooled Franklin relied on manual oiling of the OHV mechanism.
Nash started off with the OHV six to create a no "short cuts" automobile. This approach was quite successful. After three years of marketing the Nash Six, Charlie felt his reputation finn enough to introduce a lower priced auto. The quickest way to accomplish this was to use the same basic engineering of the successful six, only make it a four; the basic engineering of the Nash Four, introduced in 1921, was still current for the time. This engine had only two main bearings, otherwise the list of features reads much like the 6 cylinder above.
By 1925, Nash felt he could offer the market more than four cylinders for a similar price, and designed a whole new lower priced six cylinder. A smaller version of the OHV six that had already served so well for 7 years was developed. This engine was a three main bearing OHV that was updated with pressure fed rods. This configuration was used only for a short time as with only three mains, oil for rod numbers 2 and 5 had a long routing to travel from the main bearings. This Nash, called the Special Six, debuted in 1925; the largest series Nash, the Advanced Six continued with updates of the proven 1918 engine design.
1924/25 had to be busy years in Nash engineering, as not only was the new Special Six series developed, but a totally new and separate brand, the Ajax, was introduced. The Ajax was intended to be sold by an all new dealer network. This time Nash opted for the flathead configuration to target the market priced below the Special Six. Nash was sold on six cylinders, so the new flathead was a six, but it was no ordinary flathead six of the day. This engine boasted 7 main bearings; Nash once again providing more value than his competition.
Nash Engineering was not to rest during 1926. This (and the previous 25 years) was the time period when auto manufacturers were making significant strides in technology almost annually, same as computers were during the 70s, 80s and 90s. Just like the five year old computer of today is severely taxed to handle current programs, so were the 5 year old or more engine designs. On the heels of getting the Ajax 7 main bearing six into production, the Special Six needed a fix. Happy with the 7 main configuration where every rod was fed oil from a nearby main, Nash converted the Special Six to 7 mains, eliminating the oil delivery problems encountered with the 3 main bearing design. This engine came out in early 1926.
Following the conversion of the Special Six to 7 mains, the Advanced Six received its first major upgrade since 1918, also a 7 main bearing crank with pressure fed rods. The Advanced Six upgrade also came out in 1926. Nash Motors published a brochure called "Why 7 ?" telling the public back in 1926 about the benefits of 7 main bearings.
Also in 1926, the Ajax series was folded into the Nash family as the Light Six. By the end of 1926, Nash offered three series of autos, all seven main bearing sixes, Light Six the flathead, Special Six a middle sized OHV and the Advanced Six the original flagship OHV engine. Production rolled along through 1928 in this manner.
For 1929, twin ignition was added to the two OHV engines and all series utilized aluminum pistons. Twin ignition meant there were two spark plugs for each cylinder, two coils as well as two sets of points and 2 condensers in one distributor. Nash claimed the improved combustion resulted in greater horsepower and greater fuel economy. In addition, greater reliability was achieved as the engine could run well even if one side of the ignition system failed. (Allpar note: the new Hemi also uses two spark plugs per cylinder, and some modern engines rely on spark plugs with two electrodes. The principle was sensible and ahead of its time.)
Looking at the 1929 Nash Advance Six engine with Twin-Ignition, 278.4 CID, one notes the even spacing of the spark plugs; on the 3 main bearing engine, there was wide spacing in the cylinder head between #3 and #4 spark plugs.
Many competitors were offering middle priced eight cylinder engines by the late 1920s. In 1930, the 90 series was introduced; in basic design it was the 1929 Advanced Six updated with a timing chain to replace gears, 2 more cylinders and mains, and different bore and stroke. This 8 cylinder replaced the Advanced Six from which it was derived. So for 1930, the line up consisted of the flathead six now called the Single Six, the Special Six OHV and the 90 series 8 cylinder.
1931 saw, for the first time, the disappearance of the OHV six cylinder engines for which Nash was so renowned. As the Advanced Six had been replaced by an OHV 8 in 1930, the Special Six was replaced with a flathead eight, this time an all new engine design with timing chain and insert bearings called the 70 series (second "eight" listed in the title.) Nash's engineering effort for 1931 also included the all new 80 series OHV 8 mid sized between the 70 and 90 series. This 80 series 8 also had all the engineering advances including the timing chain arrangement rather than the fiber timing gear, insert bearings, etc. This is the 8 that Nash continued through 1942. The only six offered was the 60 series flathead simply called "The Nash Six."
The 60-70-80-90 series engines continued through the 1932 and 1933 model years. 1934 saw the 70 series flathead 8 replaced by the OHV Big Six, a six cylinder version of the successful 80 series engine. Nash was back with a signature OHV Six! The Nash Six name changed to "LaFayette" for the 1934/5/6 era still using the flathead six of 1925 origin. So for 1934, the line-up was the 10 series LaFayette flathead six, the 20 series Big Six, the 80 series Advanced Eight and the 90 series Ambassador Eight. The 90 series was dropped for 1935 leaving the 10 series LaFayette, the 20 series Advanced Six and 80 series Advanced and Ambassador Eight.
With resumption of auto production after WWII, only the 40 series flathead six and 60 series Ambassador OHV six engines were produced. These series continued through 1955. The Rambler, introduced in 1950, used the 40 series flathead, so there were still only two basic engine designs in production. The Ambassador Six was offered with a dual carb configuration in 1954/55 as did the 1954 flathead 40 series. Nash even had a few prototype dual overhead cam heads for the Ambassador produced.
The Metropolitan was introduced in 1954 with a 4 cylinder engine of Austin design. So in 1954, Nash offered only two in-house engine designs, the Ambassador Six with origins back to the 1934 Big Six and the flathead with roots to the 1941 "600". Most auto manufacturers at this point offered engines with their roots in the 1930s since auto development was arrested for much of the 1940s. Nash was not alone with these 13 to 20 year old engine designs. However, the winds of change had been blowing.
The horsepower race came with the postwar era and the resultant proliferation of V-8s. Nash had a late start in designing their own V8, so time was borrowed by using the Packard V-8 in the Ambassador 8 until their own engine was ready. Nash (by now AMC) engineering debuted their new 250 cid V8 in a unique model using the Statesman body. This 250 cid V8 was marketed as the Ambassador Special.
The horsepower race extended to the six as well in order to better move the new larger Rambler body for 1956. The quickest way to get more horsepower from the flathead six was to convert it into an OHV configuration. The flathead six was dropped in 1956 in favor of the more efficient OHV configuration and used in both the Statesman and Rambler models.
In 1957, the Statesman and Ambassador Six were dropped and the Ambassador 8 received the AMC design V-8 bored to 4 inches for a 327 cid (no design relationship to the Chevy 327 introduced years later.) The 250 cid V-8 was an option in the Rambler Custom. The limited production Rebel came standard with the 327.
In summary, there were spurts of new design activity as more technology appeared and economics allowed the development and introduction of these engines. 1918, of course, kicked off the Nash 6 series, and in 1921 the Four was available. 1925-6 represented the next era of two new 6 cylinder engine designs, followed by the prolific 1930 through 36 era of three eights and two sixes. 1941 saw the introduction of the economy engine. In 1956, the flathead six was converted to OHV and AMC introduced the all new V-8.
Nash's fine engineering developed reliable engines that powered great autos. All of these Nash engines were used well after 1957 by AMC (the flathead through 1965, the 327 V-8 through 1966, the 250 V8 through 1960, the ohv six through 1965) and in some cases, in trucks ( the 327 in IH, Ambassador six in Divco milk trucks and IH and White trucks and buses) as well as marine applications (the 327 V8.)