Anyone know what the angle differences are?
Mike
As I look into it more, the 64/65 heads have a different sized thread as well.
As for the angle, the 66 angle is straight on, which is the same for all LA engines moving forward after that - so the 66 manifold and heads will interchange with any 66 and up LA engine.
If I remember correctly, the 64/65 heads/intake had the bolt whole angled into the center, thrust and aft respectively to the center.
I've heard of people being able to just open up the intake wholes a bit more to get them to interchange, since it's not a huge difference, but don't know the exact details.
If you do a search, you can come up with more info, but here is a blurb I found:
'One issue for 273s is that the angle and size of the intake
bolts changed for the '66 model year. Later intakes can be
adapted to the '64 and '65 273 by any good machinist or
engine builder. The bolt holes have to be redrilled to
the older angle and the bolt hole openings in the intake
have to be re-spot faced to be normal (90°) to the bolt.
The '64 and '65 intake bolts were 5/16" so you also need to
use hardened washers under the intake bolt heads to take up
the slack in the 3/8" bolt hole openings and maintain the
proper torque on the early 5/16" bolts.'
