Ignition Timing R. Bortignon

What is Ignition Timing? ignition timing determines when the spark occurs in relation to piston/crankshaft position ignition timing is stated in degrees of crankshaft rotation TDC = Top Dead Center BTDC = Before Top Dead Center ATDC = After Top Dead Center ignition timing adjustment must be set correctly for best vehicle performance, fuel economy & lowest emission levels ignition timing is not the same procedure as valve timing on vehicles with distributors, ignition timing should be checked & readjusted during tune-ups & after the distributor has been removed & reinstalled from the engine timing can only be adjusted on vehicles with distributors! vehicles with DIS or direct ignition has the timing controlled by the computer and is not adjustable

How to Check & Adjust Ignition Timing connect the timing light to the spark plug wire on cylinder #1 timing light flashes every time #1 spark plug fires timing specs can be located in the under-hood tune-up decal or in Mitchell/Alldata

Follow timing preparation procedures… this prepares the engine for ignition timing refer to the under-hood tune-up decal engine at normal operating temperature vacuum advance disconnected? correct idle speed computer controlled engines disable computer’s influence on timing

Checking & Adjusting the Timing clean & paint the timing scale & notch (with engine off)

Adjusting the Timing slowly rotate the distributor while the engine is running until the marks are aligned tighten distributor hold-down bolt then re-check timing