I rebuilt an 85 305 over a year ago and have to set the inital timing at 10 -12 * to get any power out of the motor, its a TBI. All along I thought maybe the balancer had slipped on its rubber mount, but finally checked it with a piston stop and the timing mark is perfect. If i set the timing to 0* (yes, I disconnected the est connector), I can run faster that it. I am really sure I lined up the marks on the crank and cam sprocket when installed(new gears and chain), but is there a way to check this with out removing the timing cover??? And if I really was off a tooth, I thought I would have more problems. Vacuum is good 17-19 inches at idle.

 

No.

 

maybe with you setting the intial timing so high the computer is retarding the timing due to knock count, but since your initial is so high the motor runs best at this setting. would have to look at knock counts off a scan tool to determine what is best. also try 4-6 advanced at most and go from there with a scan tool and running premium. idle sounds good for a stock style cam, so i can't imagine it wanting that much timing

 

I have logged spark knock counts and need to pull some timing out of the 1600-2000 rpm / 70-95 kpa vac area, but I'll try to drop the timing back to 4 or 6 deg. and maybe in the prom bring up the SA as much as I can. I thought that by advancing the timing at the distributor, the whole SA curve would be shifted by the base amount because the ECM doesn't have any reference to 0 TDC therefore couldn't tell the difference.

 

You're right about that. The ECM only knows the initial that is programmed into it (0* for stock TBI programming). The ECM has no way of knowing you bumped it up to 10*- that is, until the knock sensor picks up detonation and starts pulling the timing back.

Might want to make sure the initial timing value is still set to 0* in the programming so you are actually getting the bump you think you are getting by cranking it up to 10* initial at the distributor.

Also- you are checking the initial timing with all computer supplied advance taken out, right (unplug the timing wire)? If you set initial without taking away the computer supplied advance it will be WAY retarded from where you think you set it. Sorry for asking such a basic question, but sometimes it's easy to overlook simple stuff.