ignition timing

[vr_powered]

Wanted to check the ignition timing on my 1987 gtx as from cold it takes a while to start (despite its recent service) and doesnt feel as pokey as my other gtx with twice the mileage which always starts on the button, so taken it for a run to get it up to temp, disconected and plugged the vacuum line to the distributors vacuum advance and got the fancy strobe out, timing is set 5 degrees before (to the left looking at the crank pulley from the drivers side) the timing mark on the lower cambelt cover, question now is what should the timing be set to for 95 ron fuel and a seperate question what would it be set to for 98 ron fuel, run both on 95 ron as 98 ron is a lot more money and fuel is expensive enough as it is

[Brunty]

I set mine to about 6 deg btdc as a rough guide. But generally, stick the fuel in you're going to use and set it by ear. You know the one, engine under load and pinking, retard a little, try again...

[Nate]

use the gun to check the advance / retard is working. then just keep advancing the timing until it pinks then back it off a touch. do that with cheap fuel in and it'll run fine on the expensive stuff too