I have a 1979 K5 with a 1986 305. I changed the timing set because the original was badly worn. Edelbrock Performer EPS intake and 1406 carb. The engine runs great at idle, but when I go to time it the mark on the distributor is off to the side at around 10 degrees ATDC. I retard the timing to where it should be, 10 degrees BTDC, and the engine won't hardly run and it diesels really bad when I shut it off. There is also no power. The harmonic balancer is good because I checked it after I changed the timing set. Any help is greatly appreciated guys. Thanks.