General information about the '76 to '79 Cadillac Seville. Subjects are "Seville history", "Cadillac colors", "Seville VIN's" and "Seville engines".

Seville engines

1976 - 1979: Oldsmobile Rocket 350

Produced from 1968 through 1980, the Rocket 350 was entirely different from the other GM divsions 350's. It used a 4.057 in (103 mm) bore and Oldsmobile small-block standard 3.385 in (86 mm) stroke for 350 in³ (5.7 L). 1968-1974 350s were painted gold, while 1975-1980 models were metallic blue, at which time the "Rocket" name disappeared from the air cleaner decal. Output ranged from 160 to 320 hp (119 to 238 kW). All Oldsmobile 350 engines had cast-iron crankshafts with harmonic balancers.

The Oldsmobile 350 was also produced with an electronic port fuel injection system, introduced in the Cadillac Seville of 1976.

1978 - 1985: Oldsmobile LF9 Diesel

The LF9 was a diesel version of the 350 in³ (5.7 L) V8. It was produced from 1978 to 1985 and was used by most domestic GM marques. 1980-1985 versions used roller lifters. These engines were notably unreliable, a situation detailed below.

Oldsmobile Diesel problems

Despite the fact that these engines looked in large part like their gasoline cousins, they were indeed quite different. The castings were much thicker and heavier, and a higher quality alloy was used for the block and heads. The main bearing journals were also increased to 3.000 inches in size to compensate for the higher operating stresses and pressures that diesels exert on their reciprocating parts. The primary problem with GM's Diesel engines of the 1970s was due in large part to poor fuel quality (diesel fuel was notoriously filthy and contaminated with water in the late 1970's), which caused corrosion in the fuel injection pump. This corrosion could (and often did) cause an incorrect injection cycle, which would produce abnormally high cylinder pressures. This in turn would cause the cylinder head to "lift" up off of the block, and stretch (or even break) the head bolts. Once the head gasket was compromised, the gasket would leak coolant into the cylinder. At 22.5:1 compression, there was little volume left in the cylinder at TDC. The uncompressible quality of liquids means that the engine would hydro lock, breaking pistons, crankshafts, connecting rods, and other parts, resulting in complete and catastrophic engine damage. Why then, did other Diesel engines, from GM and other companies, not have these problems? The answer lies in the lack of an effective water separating system, such as can be found on other diesel applications. Overall, the main ingredients of disaster that affected this engine lie in: 1) A poorly designed fuel system, which was fostered by a desire to insulate the consumer from the unpleasant aspects of Diesel ownership. 2) A misguided attempt to market the diesel engine as if it was as convenient to operate and maintain as a gasoline engine. 3) A poorly trained service staff which often used the incorrect oils and service procedures for this (and any, for that matter) Diesel engine. These factors combined to create the ultimate downfall of this engine. In the hands of an experienced diesel operator, these engines can (and often do) travel for hundreds of thousands of trouble free miles. However, for a society of people who just "gas and go", this engine was particularly ill suited to the task.

1980: 6.0L Cadillac V8

In 1980 the 425 was replaced with the L61, which was the same basic engine de-bored to 3.80 in (96.5 mm) for a total displacement of 368.3 in³ (6.0 L). The reduction in displacement was largely an effort to meet CAFE requirements for fuel economy. Fuel injection (which would be known to GM as throttle-body injection after 1985) was now standard except for Fleetwood Limousines and Commercial Chassis.

Cadillac refers to the fuel injection system as digital fuel injection; this particular induction system was later adopted by other GM division except Oldsmobile V8s.

Power output dropped to 145 hp (108.2 kW) @ 3600 rpm and torque to 270 ft·lbf (420.7 N-m) @ 2000 rpm. This engine was standard on all Cadillacs except the redesigned Seville, where it was optional.

1981: 6.0L L62 V8-6-4 For 1981 Cadillac introduced what became the most notorious engine in the company's history, the V8-6-4 (L62). The 368 had not provided a significant improvement in the company's CAFE numbers, so Cadillac and Eaton Corporation devised a cylinder deactivation system that would shut off fuel to two or four cylinders in light-load conditions like highway cruising, then reactivate them when the throttle was opened. A dashboard "MPG Sentinel" gauge could show the number of cylinders in operation, or instantaneous fuel consumption (in miles per gallon). The L62 produced 140 hp (104.4 kW) @ 3800 rpm and 265 ft·lbf (412.9 N-m) @ 1400 rpm. Cadillac hailed the L62 as a technological masterpiece, and made it standard equipment across almost the whole Cadillac line (the Seville retained its standard Oldsmobile-based 5.7 L diesel V8).

While cylinder deactivation would make a comeback some 20 years later (with modernized technology), Cadillac's V8-6-4 proved to have insurmountable teething problems, both mechanically and electronically. The biggest issue was that the engine control computer was simply not fast enough or powerful enough to efficiently manage the number of cylinders in operation, so many of these engines had their variable-cylinder function disabled by dealers, leaving them with permanent eight-cylinder operation. The 368 was dropped for most Cadillac passenger cars after the 1981 model year, although the V8-6-4 remained the standard engine for Fleetwood Limousines and the carb 368 remained in the Commercial Chassis through 1984.

1981 - 1982: 4.1L Buick V6

This engine outputed 125 hp (93 kW)

1982 - 1985: 4.1L LT8 HT4100 V8

A new engine was introduced for 1982, the HT-4100 (option code LT8). This engine, designed for transverse, front wheel drive applications, originally was slated for 1983 and a new line of 'downsized' Cadillac sedans. With the failure of the V8-6-4, however, and delays in the downsizing program (shared with Buick and Oldsmobile) that ultimately delayed those cars until 1985, the new V8 was rushed into production for the 1982 model year.

Like the infamous inline-four used by the Chevrolet Vega, the HT-4100 had an unusual aluminium block (with cast-iron cylinder-liners) and cast-iron cylinder heads. It had a 3.465 in (88 mm) bore and a 3.307 in (84 mm) stroke for a displacement of 249 in³ (4.1 L). It initially was equipped with throttle-body fuel injection, with output of 125 hp (93 kW) @ 4200 rpm and 190 ft·lbf of torque at 2000 rpm. Since most Cadillacs still had curb weights in excess of 4,000 lb (1,814 kg), acceleration was lackluster. Early engines also had significant reliability problems, most eventually resolved.


Seville history

An article about the history of the '76 to '79 Cadillac Seville written by John McEwen.

Cadillac colors

A collection of paint chip scans for the years '76 to '79.

Seville VIN's

A great resource to decode your '76 to '81 Seville's VIN.

Seville engines

An overview of the different engines you will find in the Cadillac Seville from 1976 to 1985.

Did you know

Some facts about the Cadillac Seville from 1976 to 1985.