Just got done puttin my new 13:1 big block in my 79 Camaro and cant set the timing. The marks litteraly jump from 10,20,30,40 all the way around past 180 and back to 10 so on and so forth. Tried a new distributer and a new timing light, anyone ever experienced this one before.

 

Actually not all that unusual, but it may either be a simple fix, or a bad unit. If you contact Mallory at their Tech Line they will walk you through it, and either send you the new parts, or get it straightened out.
http://www.malloryperformance.com/TechSupportHome.aspx