Hello,
I have a 1987 Caprice Estate Station Wagon with a "Y" VIN code engine (307 V8). I think this is really a Pontiac engine that Chevy put in this model. I am attempting to adjust the timing and on the Emissions sticker on the radiator cover it states to Ground C3 Diagnostic Terminal before adjusting the timing. Can anyone tell me where this terminal is located??
I did find one green connector on the end of a wire near the thermostat housing but it has 10.8V on it when the car is running. I'm not too keen on shorting it to ground unless this is the "C3" terminal. There is no marking on it anywhere. If this is not the terminal, anyone know where it is? I tried to check the timing as is but it is not even near the timing marks on the harmonic balancer so I am stuck

 

Hi there. I'm new to this forum but not to the 307.

Your diagnostic connector is under the steering column attached to the dash.

To set timing:

Start and warm engine.

With engine running jump diagnostic connector pins A and B ( 2 last pins on top row) with wire or paper clip.

Set timing to 20 degrees BTDC with light using cylinder #1 (driver side front cylinder).

Disconnect jumper at diagnostic terminal. Turn off engine.

Rejoyce, timing is set.

That green connector in front of the carb is for measuring Mixture Control Solenoid dwell, which is an adjustment on the carb.