Topic: 289 cylinder head pushrod slots

[preaction]

I always knew I should have bought Bob Mannels small block book for just this reason, were there 289 cylinder heads other than 289HP heads that came with narrow push rod slots  without the other  characteristics of the 289HP heads ? The head in question has a early  summer 65 date.

[70cj428]

If I'm not mistaken, all 65 heads have the slots, they went to the rail rockers and holes some time in 66 ....
( I originally thought it was a 65 vs 66 thing, but I recently saw an early 66 Fairlane wagon with it's original 289 and it had C5 slotted heads ...)

[J_Speegle]

One reference list the change over as May 2nd 1966 but doesn't list if that date relates to casting date at the casting plant or something else. Possibly/likely that was when the change was made from one level to the next.  Haven't looked up what the level change would have been for the before and after  engine codes.

[preaction]

John, Jeff, Thanks.

[Bossbill]

L11/L12 was the changeover to the round holes and rail rockers. See below.

Cleveland heads made the change about June 66 when L11 and L12 were made at the same time.
L11 is listed as Jan/Feb 66  for the Windsor head. Mercury date was Jan 2, 66 while Ford used Feb 15, 66.
This effectively means L12 is the change for Cleveland heads and L11 for Windsor.

These are from the Mannel book. Note that L11 is listed in Appendix A and has an incorrect year of 65. The footnote (9) lists the correct date of 66.