What's the mileage on the engine and what altitude are you at? check out boxwrench.com
how do you adjust the timing on a 1977 350 Chevy engine k-10
The 1977 Corvette 350 LS has ignition timing standard in this model. The purpose of the ignition timing is to help start the car in synchrony.
The ignition timing marks can be found on the main pulley. The timing marks will be scattered on the outside edge of the pulley.
cam timing will not change ignition timing i would try 8 or 10 degees advance at idle with the vacuum advance disconnected.
8 degrees before top dead center
what are the factory timing specs for a 1977 chevy 454
motorcraft.com shows for the 1977 F-100 with the 300 cubic inch ( 4.9 L ) straight 6 cylinder engine : ( 6 degrees BTDC ) does not specify automatic or manual transmission
Answerexample 4 before tdc :Pontiacs usually like 12-14 degrees initial advance. It's a good place to start.
chain
www . motorcraft . com ( no spaces ) shows : for a 1977 / F-250 / 300 cubic inch ( 4.9 L ) straight 6 cylinder engine The spark plug gap is .044 inch The ignition timing is 10 degrees BTDC ( doesn't specify manual or auto transmission ) ENGINE DECAL OVERRIDES
4-degrees BTDC. Before top dead center. The Heavyduty sets at 8-degrees BTDC.
Place timing marks dot to dot using a straight edge from crank center to cam centerline