[Eljaro]

Just got the engine put together after a bent valve problem which required new valve, new cam (Comp 282S) , new solid lifters and reground conrod and crankshaft bearing surfaces.
Heads are Dove F5 aluminum with a total of 9,6 compression ratio, intake is Edelbrock Performer RPM with a 850cfm all mechanical Holley 4barrel.
Advance timing with MSD 6AL is 10-13º at idle (850-900 rpm)static and 35-38º at 3500rpm.
Engine runs ok , temp is ok , but when shut off it diesels, sputters and reverses rotation very frequently.
What is the problem?Carbon deposits to glow are not possible , because the heads went in absolutely clean, mixture is on the rich side, Spark plugs are Champion RC9YCC with a 0.035 gap.
I hooked up a os2 sensor with a digital gauge and mixture is sligtly rich at idle and richer while driving at 2000-3000 rpm. Vacuum is about 15 at idle and even higher when cruising.
Water Temp is about 175ºF while driving at 90ºF ext.temp and reaches 195ºF when idling in this hot weather.
Does anybody know what else to check in order to get rid of the dieseling problem?