Jk_Under

I know people say its easy and all... I've never attempted to do it, but how would i time my 1991 RS has a stock 305 v8, it's carbed

five7kid

iTrader: (14)

First, you need a timing light.

Next, disconnect the vacuum to the vacuum advance on the distributor (can we assume a vacuum/mechanical advance distributor was installed when it was switched to carb?). Hook up the timing light - most use power leads, one positive and one negative to the battery, then a clip-over for the #1 spark plug wire. The #1 cylinder is the front driver side cylinder. Start the engine, aim the timing light at the damper (most timing lights have a trigger you need to depress to get it to flash), look for the timing mark on the damper and where it lines up with the timing tab on the front cover. The timing tab is marked in 2 degree increments. When facing the engine from the front of the car, advanced is to the left, retard is to the right on the tab.

With a carb, you want between 8-12 degrees before top dead center (BTDC) at idle with no vacuum on the vacuum advance. If it is outside that range, loosen the distributor hold down clamp bolt so you can rotate the distributor body. Counterclockwise advances timing, clockwise retards timing. It doesn't take much movement to change the timing.

When it's where you want it, retighten the distributor clamp, and make sure the timing hasn't moved.

It's a good idea to watch the timing mark as you increase engine RPMs. It should advance with more RPMs - that's the mechanical advance. Then hook up the vacuum advance and check again. It should be more advanced at idle, or advance should jump up when you open the throttle a little over idle. When RPMs are steady at, say, 2000 RPMs, the timing mark should be well left of the timing tab - that's the combination of mechanical and vacuum advance. When you give it a lot of throttle suddenly, the timing should back down, then go back up - that's the vacuum lowering with more throttle, then catching up as vacuum increases again.