Throttle Linkage trouble

[Milly]

Hi,

I'm having a few problems with my 356 throttle linkage..!

I'm only getting the carbs about 2/3rd's open (if that) from the pedal travel.

Having traced the linkage from the pedal assembly I can get full travel of the pedal when the cable is disconnected, so it wouldn't seem to be that end.

It would seem that the problem lies at the bell housing end, in that when underneath the car and you push you're foot down on the accelarator it doesn't move the linkage enough to open the carbs fully. (so that when you push the carb linkage down at the engine end you can still get about another third out of it. However if you manually hold the carb linkage down and then keep your foot on the pedal and let go of the carb linkage, it doesn't go back to the original travel from the accelerator and keeps the carbs fully open).

This would suggest to me that the accelerator cable from the pedal assembly to the bell housing is to long, but when depressing the pedal it seems to stick (not get full travel) and not move the bell housing linkage that extra few mil required to open the carbs fully..! Only when depressing the carbs manually does the bell house linakge move that extra few millimetres..!

I don't know if any of this makes any sense, I'm as confused as Sandy Tosvik caught between going to a midget or lesbian conference..!

I spent 3 hours under the car yesterday just getting more and more confused..!

Any ideas would be greatly appreciated..?

Cheers in advance

[Nige]

I don't know if any of this makes any sense, I'm as confused as Sandy Tosvik caught between going to a midget or lesbian conference..!

We still do the impression of her that Vic and Bob did on Shooting Stars, always good for a laugh that one.

Sounds like your cable maybe too long, but then you should be able to adjust that at the carb end, take up the slack.

Is there anything interferring with the pedal movement, carpet, foot boards, is anything bent?

I'm not up on 356 motors, but I guess the cable passes through the fan housing to the carb linkage? If it does, does it pass through a tube/conduit? If not it maybe be snagging on the steel walls of the fan housing.

Do the carbs still have their return springs attached? have they gone weak and need replacing?

Is the cable route correctly?

You might want to disconnect the cable and check that each end operates properly, i.e. carbs returning by themselves, pedal assmebly clear from obstructions and nicely lubed, check that nothing is bent out of shape.

Hope this helps.

[Mike Smith]

Milly - You have a problem - - It takes time

Here is a reply by Ab on the 356 Talkpage - Posted last week

If this is a RHD car, let me know because you need to check something else

Mike
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is a fundamental design dimension that should serve as the
starting point and it should be preserved when you are finished.

The center of the ball on the little bell crank that attaches to the fan
housing and connects to the pull rod coming up from the bell crank at
the transmission should be 50 mm from the vertical surface of the fan
housing. This is the starting point.

With the pull rod free from the transmission bell crank and the push
rods free of the carburetor connection, adjust the near vertical push
rod that connects the aforementioned little bell crank with another bell
crank on the cross shaft to obtain approximately a 15 degree angle with
respect to horizontal of the lever that connects the cross shaft to the
carburetor lever arm via the carburetor push rods[still free at this
time]. Secure length. This rod has right hand threads both ends so it
will be necessary to take one end off to adjust. Next adjust the idle
advance screw [not the idle mixture control screw] until it is
completely off the stop. Turn the screw until it just touches the stop
and advance it 1/2 turn more, same on each carburetor. This will assure
that the butterflies are not resting against the throttle bores. Now
adjust the length of the carburetor push rods until the ball sockets can
be engaged without compression of the rod and secure this length. These
rods have left and right hand threads and the left hand thread is always
installed at the carburetor. This is an easy pick-up for the engine
judge. There will be a nut permanently attached to the right hand
thread. This is used to turn for adjustment and hold for arrestment.

Disconnect the pull rod that runs up through the tunnel from the bell
crank at the transmission. Install the pull rod at the bell crank on the
transmission and connect to the little bell crank behind the bell crank.
Note angle of bell crank with respect to a reference line on the
transmission case. Actuate bell crank at transmission for full travel
and note angle with respect to the previously chosen reference line.
Adjust the pull rod to the fan housing crank until these angles are
equal [referred to in original post as..." perpendicular to the
linkages"?]

With the pull rod connected to the bell crank near the accelerator
pedal, adjust the length of the pull rod [socket adjustment] until it
can be engaged at the transmission bell crank without compression.

Now for a test of "full throttle".

Depress accelerator pedal until it touches the stop on floor while an
assistant looks down the carburetor bores. If near vertical, you are
done. The stop on the carburetor should have clearance.

If not, two options. You can lower the stop or you can change the angle
of the pedal. There is another push rod that connects the accelerator
pedal and the bell crank under the floor boards. To make the latter
adjustment, you will need to get under the mats and the boards, etc. It
all depends on the angle of the pedal that feels right throughout the
motion. It cannot be leaning back too far or require the foot to push
too much forward--a balance of feel so to speak.

It is a fiddling task, but the above has worked for me for more than 45
years. Starting from scratch it will take 2 hours minimum.

Ab Tiedemann