You can try by vacuum- try to bring it to 20 Hg at idle, but a timing light is much more accurate
You failed to mention if it is automatic or standard shift. Also the engine size would be a great help. Without more information it will be impossible to give you an answer.
The degree timing for a 327 cubic inch engine for a Chevrolet Corvette with is 4 degrees before top dead center. This engine is rated at 300 horsepower.
All 1963-1968 Ford 289 V8 engines had the timing mark located 45° to the left of center, with the engine at TDC. (This is the left side of the engine, not the observer). There was a timing pointer cast or bolted to the timing chain cover, and the TDC and degree marks (typically 0-12°) were stamped on the harmonic damper/balancer.
Timing Chain.
www . motorcraft . com ( no spaces ) lists: 1968 Ford Mustang - 289 cubic inch V8 engine Ignition timing is ( 6 degrees BTDC ) Point gap is ( .021 ) Point dwell is ( 24 - 29 ) unless the engine compartment decal shows different
The point gap for a 1968 Ford with a 360 Engine are .017 without European Commission and .21 with European Commission.
For a 1968 Cougar with a 302 ci/ 2 bbl carb, you will want to set the timing at 6*B from TDC
they were a blue color. I have a 1968 and it is red; later models were light blue.
Do you mean firing order? If so it is 1, 8, 4, 3, 6, 5, 7, 2.
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Remove distributor cap Have assistant crank engine over Observe whether or not distributor rotor turns as motor turns over