Two engines and four fuel systems types are used to power your Astro/Safari Van. Depending on the year and model, your van could be equipped with a 2.5L (151 cu. in.) engine (1985-90) or a 4.3L (262 cu. in.) engine (1985-96). The 2.5L engine was only produced with a Throttle Body Injection (TBI) fuel system, while the 4.3L engine varied from a 4-bbl carburetor for 1985, TBI for 1986-91 (as-well-as some models from 1992-94), a Central Multi-port Fuel Injection (CMFI) system for some 1992-94 and all 1995 vehicles or a Central Sequential Fuel Injection (CSFI) system for 1996 models.
On the 1985, 2.5L TBI engine, the cylinder head and engine block are both constructed of cast iron. The valve guides are integral with the cylinder head and the rocker arms are retained by individual threaded shoulder bolts. Hydraulic roller lifters are incorporated to reduce the friction between the valve lifters and the camshaft lobes.
On the 1986-90, 2.5L TBI engine, a few changes appeared, such as: (1) the pistons were replaced with hypereutectic types (pistons embedded with silicone nodules in the walls to reduce the cylinder wall friction), (2) a reduced weight, high efficiency alternator and (3) a variable ratio air conditioning compressor.
Although there are different versions of the 4.3L engine, depending on the VIN and fuel system, the main design is the same. All are 90 degree, V6, overhead valve, liquid cooled engines with cast iron block and cylinder heads. Many of the early 4.3L engines use swirl chamber heads (to increase power and fuel efficiency). The engine block and cylinder heads are constructed of cast iron. Other major features are: a wider oil pan flange, raised rails inside the cylinder heads (to improve oil return control), machined rocker cover seal surfaces, a trough along the rocker cover rails (to channel oil away from the gasket) and even distribution of the clamping loads, to make this engine one of the most leak-resistant on the road today.
In 1986, the 4.3L TBI engine began using a new one-piece rear crankshaft seal, lighter engine oil, remachined camshaft lobes and new poly-vee alternator drive belts.
In 1987, the 4.3L TBI engine began using roller valve lifters instead of the standard flat bottom lifters. The roller lifter is still hydraulic requiring no valve adjustment. The roller lifter incorporates a roller that rides along the cam lobe reducing friction and component wear. A roller lifter restrictor and retainer is needed to keep the lifter from turning in the bore while the engine is running. All 2.5L TBI engines incorporate the roller lifter configuration.
In 1992, the introduction of the VIN W (CMFI or CSFI) motor saw the latest improvements in the 4.3L engine family. The VIN W motors are equipped with a cast iron balance shaft mounted in the crankcase, above the and inline with the camshaft. A camshaft gear drives a gear which is attached to the balance shaft. The VIN W's unique fuel system requires the use of a two piece manifold, with integral throttle body. These cast aluminum pieces house the central injection system (injector or injectors, depending on the model). For more details on the CMFI and CSFI fuel systems, please refer to Fuel System of this information.