I am having trouble timing my chevy, its a 350, My car is running at 21 degrees initial advance and 31 overall but runs low-mid 13s, retarding it made me run 15-16s. advancing it seems to hurt me a little but not completely sure. Why is my car holding so much initial advance and is this hurting my quarter mile time or my engine. Cant hear any detonation but will I considering i dont have much overall timing. 31 is at 3 grand and 21 at idle, what could be wrong?