timing questions for '68 318
Either you
do not have the cam properly aligned (one tooth off)
or the balancer outer ring has slipped
or the balancer / timing tab are not matched, IE early to late
or a massive factory defect means that something was manufactured incorrectly
It is VERY difficult to "find" TDC by FIRST using the cam marks, as you have a certain amount of "dwell time" there
What is much easier is either use a piston stop to locate TDC or to first PUT the engine on TDC using the timing marks, them remove the cover and THEN look at the cam and verify it is correct/ not