Well, you learn something new everyday. So the heat riser flapper thing went away in '69 and came back again as part of the emission control system in the mid '70s?
Jack, that center port divider is another thing the Pontiac engineers changed their mind on- I've got a bunch of sets of logs and only a couple have the divider. I don't recall the dates on the ones with them or without.
The set on my Lemans right now are '70 castings that don't have the divider.
BTW, my lemans ran a 12.76 at Lebanon Valley yesterday with logs... and G70-14 Polyglas tires. Those log manifolds aren't the hinderance that most people believe!
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1966 GTO
1969 Lemans Convertible- F.A.S.T. legal family cruiser. 12.59 on G70-14 Polyglas tires. 1.78 60'
1969 Bonneville Safari- cross country family cruiser. .
1979 Trans Am 400, 4-speed, 4 wheel disc.
View from the drivers seat racing down Atco Raceway-
http://www.youtube.com/watch?v=GhYDMdOEC7A
Ride along in the other lane-
http://www.youtube.com/watch?v=mIzgpLtF_uw