AMC Straight-6 Engine - 195.6

195.6

American Motors' first straight-six engine was the 195.6 cu in (3.2 L). It was produced from 1958 through 1965 in both overhead valve (OHV) and flathead (L-head) side-valve versions.

Sometimes referred to as the 196 engine, this engine was originally designed by Nash and introduced in the 1941 Nash Ambassador 600 model. It featured only four main bearings, unlike the 7-main-bearing 234 flathead engine it replaced. It was a flathead design displacing 172.6 cu in (2.8 L). It was later enlarged to 184 cu in (3.0 L), and finally to 195.6 cu in (3.2 L). It was redesigned as an OHV engine in 1956. The flathead version was discontinued for 1956–1957, but reemerged in 1958 as the economy engine for the "new" Rambler American. When the engine was changed to an OHV configuration the water pump was moved from the left side of the engine (driven by a shaft extending from the back of the generator) to the front above the timing chain. When the flathead model was reintroduced it also received the new water pump. Equipped with such high quality parts as forged crankshafts and connecting rods, these engines earned a reputation for remarkable durability. The flathead, however, was prone to the typical flathead problem of overheating under sustained heavy load. This was from the hot exhaust traveling through the cylinder block to the exhaust manifold.

American Motors introduced a die-cast aluminum block version of the OHV 195.6 cu in (3.2 L) engine in 1961. It was produced through 1964. This engine used cast-iron cylinder liners and a cast-iron head. The cast iron and aluminum block heads are of similar design, but will not interchange. The aluminum block is slightly wider than the iron block and the bolts on the left and right sides of the cylinders are further apart.

The 196 OHV requires more periodic maintenance than newer-model engines. The head bolts must be re-torqued (retightening process) regularly. Factory service manuals recommend that head bolt torque be checked every 4,000 mi (6,400 km) and to re-torque them every 8,000 mi (13,000 km). With modern head gaskets this service interval can be extended to re-torque the bolts every 12,000 mi (19,000 km), or every other year. The cause of the headbolts loosening over time is believed to be thermal expansion and contraction of the head due to the rather massive design. The head expands and contracts by as much as 0.020" in length during normal operation. This loosens the bolts over time and eventually causes the seal between the head and block to fail. This maintenance is imperative to prevent the engine from running hot (the first sign of a blown head gasket) and thus warping or cracking the head. The cast-iron liners in the aluminum block version can also shift if the head bolts are not properly torqued and the engine is run hot. Good replacement heads and aluminum blocks for these engines are now difficult to find. To make matters worse, the aluminum block head is similar in design to the cast iron block head (both heads are cast iron), but they will not interchange. The aluminum block head is roughly 1/8" wider than the iron block head and uses a slightly different head bolt pattern.