Early 964 throttle chamber adjust

[Ravioliv]

Hello,
still rebuilding my engine, I inspected the intake parts en while cleaning the chamber I realized that the throttle did not seem to fully open when moving manually the lever to the mechanical stopper.
Actually ( like all 964 I suppose ) I have 2 throttles.
1 small on the top and 1 bigger below.
what happens is during the first mm only the small one moves, until the lever in the mechanism ( the one pulled by the cable ) get in contact with another part that acts on the bigger throttle command.
It is possible to adjust the distance between the two stops by 2 screws which can modify the moment the second throttle starts to open ( see picture below )

the

What happens is when the main lever ( pulled by the cable ) is reaching the mechanical stop that is normally corresponding to wide open position, the big throttle can still be opened by a significant angle...as if I would be missing some opening potential....

This could be changed by acting on the 2 small screws but I think the adjustment is factory one and I don't want to mess it up.....

Here is a video of the amount of free play to give an idea


Is that " normal" or am I losing some power at full load?...
If not normal how to adjust the synchronization between the 2 flaps?....

Thanks a lot!

[HawgRyder]

This sounds like the old 4 barrel carb type adjustment.
The primaries were instant (following throttle position)...and the secondaries came in later (to prevent "bog" or stumbling) as the RPM's went up.
Perhaps changing the position of the primary/secondary action can be used to your advantage.
With the secondaries closed...you would get better torque at the bottom end (low RPM).
The change-over point could be custom adjusted to give you a smoother transition in driving.
As long as the secondaries are open at full throttle (giving max power) you should be good.
Bob

[Ravioliv]

Ok, so the fact that it does not open fully looks abnormal? ( I am pretty sure it is factory condition...)

[RedCoupe]

I always believed that it wasn't just a mechanical linkage between the two butterfly valves, but I haven't ever checked mine to be sure either. Supposedly, the second flap opens at 5,500 rpm, so I always believed that there was vacuum diaphragm or something else involved in addition to just a straight mechanical linkage.

[Ravioliv]

Originally Posted by RedCoupe

I always believed that it wasn't just a mechanical linkage between the two butterfly valves, but I haven't ever checked mine to be sure either. Supposedly, the second flap opens at 5,500 rpm, so I always believed that there was vacuum diaphragm or something else involved in addition to just a straight mechanical linkage.

What you describe is a different flap, it is the one further inside intake manifold that is activated through a vaccum system.

Mine is the main butterfly that is linked to accelerator cable

Actually the big one starts to open really at small angle, My "concern" is that at full throttle the main butterfly is not fully opened as shown in the video....but maybe it is correct like that....if not I am not sure how to adjust it....