I HAVE A CHEVY 350 WITH AN EDELBROCK CARB 650, 1 INCH SPACER, PERFORMER INTAKE, HEADERS AND 3 INCH EXHAUST. HOW FAR SHOULD I ADVANCE THE TIMING?  

What is CR of engine, cam type and desired octane fuel and is it a stick or automatic? Furthermore, for what it is worth, 3 inches is WAY too big for duals on a 350. (big even for a BB)  

automatic transmission, stock cam, 87 octane, just want to know if I should set it to stock timing or advance or retard it some. Stock setting is 8 degrees before top dead center.  

What year is engine and the CR (compression ratio) as this is a factory with 87 octane for engine timing.  

its a 1972 and i dont know the compression ratio.  

Okay, I do if engine is stock internally. (I owned a 72 GMC 4x4 for many years that I got when it was less than 2 years old) A engine of that era likes about 36 to 38 degrees of total advance at around 3800 RPM and more. What your static timing is will depend somewhat on the advance built into distributor and octane of fuel. I do not think you are going to be able to run full advance with 87 octane in that engine as it will want to knock badly at times if you do. I think I would try 4BTDC and see if that works knock wise with 87. If you run 89 octane or better I would try 10 BTDC or a bit more. One more question, are you using vacuum advance and is it manifold or throttle vacuum from carb powering it.