Hoyt....we used an advance feature timing light and got our 10 degrees advance which is on the RH side of the timing pointer. Mr. Langdon said 10 to 18 degrees and our truck runs great at 10 with 18 vacuumm. You are correct without an advance feature timimg light we were up the creek. What was confusing were all the terms and what they equaled (not just before top dead center and after top dead center) but also BTC=retard....ATDC=advance...once I got that ( a big bag of DUH ). It sort of all came together ( with the help of a lot of people on this forum) with the advance feature on the timing light....T/C Steve