Pre-'69 Timing Marks vs. Crank Keyways (Redux)

[Wayne M.]

Further to interesting thread of 4 August (Steve, Duke, Tracy, Michael et al), Found some GM engineering drawing information in Colvin's '65-'69 By-the-Numbers book; page 251, (lower left corner of blueprint) is a timing diagram for '67/'68 low horse SB camshaft # 3896930. Shows crank keyway centerline at 45 degrees when #1 piston at TDC and harmonic balancer line at "0" on tab of timing cover.

Do these angles apply also to big blocks ? What was the reason for the 10 degree change in 1969 ?

[Michael H.]

Re: Pre-'69 Timing Marks vs. Crank Keyways (Redux)

Thanks Wayne. The change was due, in part, to the fact that the new extended leg SB water pump was to be used starting in 1969 and the timing tab/mark would be easier to see through the gap between the engine block and water pump. The longer and wider legs of the new pump would have partially hidden the timing tab in it's current 68 location. Also mentioned in some GM paperwork at the time was a new larger power steering pump that would have made the tab difficult to see in it's original location but I don't think the new pump ever made it to production.

The keyway and key would have been in the original 45 deg position on the new 69 dampner. Only the mark on the outer dampner ring changed location by 10 deg.

Michael