I have a quick question. I understand that in my 91 305 Z28 Camaro the timing is controlled by the computer. So does this mean that I don't have to check for the timing using the usual approach of using the timing light, loosening the distributor clamp-on and adjusting the timing until it is within specs?. I checked my timing the other using the timing light and disconnecting the EST cable. I found that the timing was like 6 or 8 degrees after dead center which is very far from specs which say I think 6 degrees before top dead center. Before taking the time to adjust the timing manually I would like to know if we are really supposed to fix this problem or the computer will take care of it? I read somewhere that since timing is computer controlled we should not adjust it mechanically. Thank you.

 

These cars do have the timing adjusted by the ECM but that is based off of the manualy pre-set base value. So you can check and change the base timing just as you did. If it is off, the ECM will limp the car along until the base is set correctly in the manor you described. You must unplug the EST so that you do not get any ECM interferance when dialing in the base. I am not sure what a good base is for TPI. I have a pretty good feeling that it is just like any other fuel injected 3rd gen small block and that 6° to 8° is fine. You always want to be cautious when setting the base timing. You can go too high even if you do not hear audible ping. Audible ping basically means that it is beyond what the ECM can compensate for. A datalog will show you what knock counts are present to varify that your setting is kosher. You can also try the old track method and watch your ET's and go off of that.