Originally Posted by Xr7GT
I have a stock 67 Cougar GT with 390. It has points. It is low miles and not rebuilt. It was a California smog package engine but the smog pump and attachments have been removed. The timing settings are listed at 6 BTDC for the smog engine and 12 for non-smog. I had set the timing at 12 and it pings really bad at WOT. I am running prem fuel. Setting it at 6 BTDC seems a little low and I have to really adjust the idle screw up to keep it running at idle. Is there some other mechanical aspect of this "smog" engine that I need to set it at 6 BTDC and will I be doing any damage by running above 6.
The FE was always sensitive to octane rating of the fuel it burned. Add age, combustion chamber deposits, and the cam coming out of coordination with the crank due to timing set wear, combined with unleaded fuel and you've got a recipe for detonation.
The fact that you need to really adjust the idle up is a good indicator that the timing set has fallen retorted due to wear. Restoration of the gears and chain should wake the motor up even with 6 degrees of advance.