with the breaker bar move the dampener till the rocker arms on either the #1 or the #6 cyl you are working with are at the same height (amt of open or closed). go back & forth a bit till you get it (the height) dead on. at that point the dampener slit must be within a degree or two of TDC on the timing marks. this will confirm (hopefully) that you are good dot to dot and there ain't no gross errors in the crank keyway (wouldn't be that IF it ran OK prior to rebuild ex for being worn out) or the new timing gear keyway slot or where the dot was (mis)stamped or if a person used the wrong dot or a cam can be fubared (rare tho).