Timing Marks - 1992 4.3

1992 Astro, 4.3 with a Z in the VIN #
While playing with the transmission (tonite's lesson was the value of having a transmission jack) - I looked up at the front of the engine
and was surprised to see what appears to be two grooves cut in the whatchamacallit (harmonic balancer?) for timing marks. Are they indeed both timing marks? If so, which one are you supposed to use when you time it?
Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Somebody has to have an answer
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.