Engine Timing and Carburetor Air/Fuel Ratio Adjustment 83-84 305 SBC

[Tynan918]

OK ... I finally have the starter button installed and working correctly, the alternator wired, charging, working correctly, no battery drains, replaced the flimsy throttle and kickdown cable bracket, got my throttle cable secured to the carburetor, and converted from an electric fuel pump to a mechanical fuel pump...

Started the engine, warmed it up, and ran it to swap parking places...

But because I had to remove the distributor in order to install the throttle cable bracket, and turned the motor over after I removed it, I need to get my timing light on it and set the timing over again. I also would like to adjust and correct the air/fuel mixture screws on the carburetor...

Which one should I start with ? The timing or the air fuel ratio ?

 

[Tynan918]

Initial Timing should be 8-12° BTDC @600 rpm ?

...And then Total Timing @32-36° @2500-3000 rpm ?

Correct ?

 

[DRIVEN]

Mechanical>timing>fuel

 

[MrSony]

You set your idle speed with your timing, basically. You can't adjust anything fuel related until your timing is squared away.

 

[Tynan918]

You set your idle speed with your timing, basically

So once base and total timing is set, I then set my idle speed ?

But shouldn't idle speed be 600 rpm when setting base timing ?

 

[Tynan918]

 

[MrSony]

Your carb must be set up properly from the get go. Set transfer slots to a square, no more, no less. Install the carb, fiddle with timing to get it to idle, get it to idle where you want by adjusting initial timing and fuel mixture. You kind of have to chase your tail a bit, but this is the "correct" way to chase your tail.
You then do a final tune with a vacuum gauge to get the highest reading you can with timing and fuel mixture at idle.

 

[MrSony]

 

[Tynan918]

My initial timing is set at 14° BTDC...starts right up just bumping the starter button.

Waiting on a helper to set total timing...that should be 34 to 36° BTDC @ 2500 to 3000 rpm right ?

 

[Tynan918]

I'm reading 3 different scenarios when it comes to initial and total timing on a SBC...

Scenario 1, Factory Settings: Initial is 6° BTDC @600 RPM in Drive, but doesn't specify the total timing...I'm guessing 34-36° total with the initial being 6°.

Scenario 2: Says here, with the vacuum advance hose disconnected and plugged at the hose, to:

1. Set the initial timing to 4° BTDC.

2. Connect the vacuum advance hose back to the distributor vacuum advance canister...timing reading should advance 18° plus or minus two.

3. Raise the RPM to 3000 and the timing reading should show 32° total timing, and if not, advance or retard the distributor to achieve 32° total timing.

How to Time a Chevy Small Block Motor

To establish the correct advance curve, the vacuum advance and mechanical advance in the distributor must work properly with no binding. When a small-block Chevy is started, the spark is retarded to 4 degrees BTDC. As soon as the engine starts and a vacuum is produced, the vacuum advance...

itstillruns.com

Scenario 3: 12-18° BTDC initial timing and 34-36° total timing...

Which one is correct ? I'm willing to bet my cam, lifters, rockers, and H.O. heads are stock.

Should I start with the factory settings of 6° BTDC @ 600 idle rpm and total it at 34° ?

The other options outside of the factory settings didn't specify what the RPM needs to be when setting the initial timing...does it even matter or should it be higher when setting the timing at higher degrees BTDC?