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Old Car Tune-Up

Carburetors, distributors with points, mechanical fuel pumps...these marvelously basic components were found on virtually all cars built before the advent of modern electronic fuel injection and control systems that essentially operate in a state of “constant tune”. Vintage cars with their basic mechanical ignition and fuel systems required frequent adjustment or “tuning” to keep them running at peak efficiency and power. These systems required equally basic and uncomplicated tools to perform troubleshooting and tuning procedures. You'll also need a vintage or reprinted shop manual covering your specific model car, as these manuals provide a wealth of information, methods and specifications unique to your car and engine.

Follow along as we describe each tool and their specific use:

Vacuum Gauge –
The Vacuum Gauge is perhaps one of the most useful yet most underused tools in the group. It reads engine intake vacuum. With it you can:
-- Adjust the carburetor for the best fuel mixture at idle. After properly setting and tuning the ignition system, set the idle to the manufacturer's specified RPM, find a usable vacuum port on the engine's intake (often 'T"-ing into the distributor vacuum advance port is best). You can then lean or richen the idle mixture screws to obtain the steadiest and highest needle reading at the specified idle RPM.
-- Identify sticking or burned valves or damaged seats as well as a leaking head gasket. A quickly fluctuating needle will indicate one of these conditions.
-- Find an exhaust restriction. A gauge reading that is lower at a constant 1500 to 2000 RPM than the idle reading indicates excess exhaust pressure.
-- Locate a vacuum leak. A low needle reading at idle dropping to nearly zero when the throttle is opened will reveal a vacuum leak in a hose, fitting or intake gasket or worn piston rings.
-- The vacuum gauge will also read pressure up to 10 PSI and is used to test for adequate fuel pump pressure and reveal internal leakage.

Compression Tester –
-- The Compression Tester will reveal much about the condition of individual cylinders and the overall health of an engine. In use, the spark plugs are removed, the ignition disabled, throttle blocked open, and the appropriate fitting is threaded into the spark plug hole.
-- Identify a leaking cylinder head gasket. If two adjacent cylinders display readings significantly lower than the manufacturer’s specifications, a compression leak likely exists between cylinders.
-- Leaking piston rings can be identified by a reading that builds by cranking the engine to a point, yet does not develop specified compression.
-- Damaged or leaking valves will reveal low readings that do not increase during cranking.
-- Readings that exceed manufacturer’s specifications can be attributed to excessive carbon buildup on pistons and combustion chambers.

Timing Light –
The Timing Light is used to set the ignition timing. This is the point at which the number one spark plug fires while the piston in the number one cylinder is near to or at the top of its travel on the compression stroke. This is important to allow an engine to deliver the maximum power and efficiency designed into it.