Chevrolet introduced its first inexpensive, mass-produced V8 engine in the mid-1950s. The original Chevrolet small block engine displaced 265 cubic inches and was designed with future enlargement in mind. In 1969, the small block engine was enlarged to 350 cubic inches. The Chevy 350 was used in many different General Motors vehicles into the 1990s. A tune-up of a Chevy 350 requires focusing on certain aspects of the engine and adjusting them properly.
Spark Plug Gap and Breaker Point Gap
Because the Chevy 350 is an internal-combustion engine, spark plugs are necessary to initiate the explosion needed to force the pistons up and down. A spark plug is a cylindrical device threaded into the block. The grounding strap attached to the side of the plug must be a certain distance from the centre electrode to perform properly. The gap between the two should be set to .035 inch with a spark plug gap tool. The breaker points are located in the distributor and regulate the electrical current to the ignition coil. The breaker points should be set to a .19-inch gap with a feeler gauge.
The dwell angle is the duration the contact breaker points stay open, allowing the ignition coil to energise. A dwell meter connected to the engine can indicate the current dwell angle, while adjustments can be made to the dwell angle in the distributor. The correct dwell angle setting for the 350 engine is between 28 and 32 degrees.
Each of the eight cylinders on your Chevy 350 requires spark at the correct interval. This is determined by the firing order, which is useful when replacing spark plug wires to ensure none get crossed. The firing order on the Chevy 350 engine is 1-8-4-3-6-5-7-2.
The ignition timing on your Chevy 350 engine must be set correctly so each cylinder receives its spark at precisely the right time. The timing mark is located on the harmonic balancer at the front lower side of the engine block. The timing should be checked with a timing light and set to 4 degrees before top dead centre.
The correct idle speed must be checked with a tachometer connected to the engine while it is running. The idle speed for vehicles with a manual transmission should be set to 450rpm and to 600rpm for vehicles equipped with automatic transmission. The idle speed is adjusted by turning the idle adjustment screw on the carburettor.