Hi,

I am the crazy Austrian that bought a 69 California vette last year

all is fine so far, vette is doing very well, but :


If I go full speed, pedal to the metal for some seconds,

sometimes - not always engine stays up between 1500 and 2000rpm

one ore two more soft touches of the throttle make it come down to 700

As far as I could see there is a spring ......I think its too weak because if I stop when the engine turns too high and take off the air filter I can solve it with touching that spot and helping the spring to turn it back.


Any Ideas where I can order such a spring ?

(I have tried some times to lubricate all spots to make it go easier, but I think its just the weak spring, all works fine so far)

 

The real effect on your idle is with the thottles return to the idle position. See the screw at the top of your red arrow in the picture? The throttle level at idle should be touching the screw unless the choke, or other bind or accelerator linkage is hanging up the idle. I would:

- Spray carb cleaner on all the linkage both sides of the carb
- Check the return spring (the large one) that it is returning the throttle back to the idle screw.
- Check the accelerator linkage to make sure there is some play on control of the throttle. If it is too tight or binding, idle will be erratic. Also, spray some wd-40 on the linkage of the acc cable to make sure it works free.
- Disconnect the accelerator linkage at the carb and move the carb throttle slowly to make sure there is no bind in the carb. Then reconnect and do the same.

The spring you are referring to in your picture unless broken or binding on the linkage is not going to hang up the idle like you are getting. Clean all up and make sure it moves freely with no bind.

 

strange ....

now I've been out at the car

after putting off filter red and black arrow were together, no gap to see ad screw

once I moved it and now there is no chance to give it back where it was

seems for me as choke has done this gap .....

 

Sounds like you need to adjust the Fast Idle. Do a search, there are some good resources on the forum for setting up the Rochester.

 

Most probably the constant primary shaft movement has caused the carb body to wear, and the throttle is sticking partially open. Qjets are famous for this. Wiggle the bellcrank where the springs and throttle cable are attached. If there is radial play, there's your problem.

 

is this what you are talking about ? (step 38-40)

 

thats what you meant ?

there is little radial play, not too much but to feel, about 0,5mm I would guess

so you think thats the reason ?

what did people do that also had that play ?

 

the other one left of it (black arrows) has also play but a little less than the right one with red arrows

 

When you are working on this problem, you need to continually check the position of the [lower] throttle plates by looking down into the carb.

I suspect that you have some kind of interference between those lower throttle plates and the spacer/gasket/intake manifold. To test this, look down into the carb bores while manually exercising the throttle linkage. When releasing the linkage, allow it to return to idle position on its own, then manually force the linkage to its idle stop to see if the carb is not completely closing down on its own.

{Important note: When working with the carb/linkage, you should disconnect the accelerator pump linkage so that raw fuel is not dumped into the intake manifold every time the linkage is moved. Use a small pin or punch to drive the roll pin toward the carb inlet so that the accel pump arm will no longer be activated by the linkage. Make sure that you don't drive the pin all the way to the carb housing, as you need a little gap behind it in order to pry it back into position when your testing is done.}

If you find any binding of the throttle plates, loosen all four carb mounting bolts and exercise the linkage again. Often, this will reposition the carb properly. Otherwise, you can manually move the carb around a bit and try the linkage to find a spot where there is no binding of the plates. Then, just tighten the bolts down again; but only apply the torque required for those bolts...first, snug all bolts down; then apply 144 in-lbs (16.6 N-M; 1.66Kg-M).

If this is not the cause of your problem, then you must have another item binding up: accelerator pedal linkage; throttle cable; linkage on the carb; inadequate return spring; etc. Test each separately to locate the item that is binding.

Good luck to you.

 

It's the one with the black arrow, primary barrels. The play would be fore/aft, not so much vertical.

 

No, black one has nearly no play ...

maybe I didnt describe it as good as I wanted to ..... once more :

when it happens (one of ten times maybe) engine runs at 1500 - 2000

then I stopped driving and put off air filter completely, so I could touch the shaft with red arrows and the spring on the shaft.

I looked inside and saw it open a little at secondarys, when I touched the secondarys shaft and helped to turn back just a little engine came down to 700 and all was fine again.

Thats why I think the spring on the shaft could be a tired one

 

The spring is fine. The excess play (0.5mm) is allowing the shaft to get 'stuck'. Usually it's the primary shaft that wears excessively- yours appears to be worn on the secondary. Same net effect, high idle speed.

 

In all the pictures the end loop of the outer spring is not in the hole in the throttle linkage. He functionally has only one throttle return spring working.


Beide drosselklappen zurück federn in das Loch der throttle linkage. Die äußere Feder ist nicht in das loch.

 

seems to be so at the pics above

so I made 2 more pics, 1 of each side :

 

In the new pictures I can the spring is in a different hole. Can you place the inner spring into the same hole as the outter spring and the straight end of both springs should be on the throttle linkage not the bracket.

http://vetteprojects.com/kstyer/imag...ture%20014.jpg

 

pop the throttle cable and see if that fixes it. In your new pics there's a funky angle from the cable bracket to the throttle. Might also check your choke rod for smooth operatiing. With that non stock high rise manifold you couldn't have used the stock rod.

 

Almost looks like there is no gasket between the manifold and the carb.
As stated earlier, you need to be sure that the throttle plates are returning to the same position every time, by looking down the bores. Actually look at the plates.

 

Agree, on my Qjet I have both return springs installed in the same hole, it seems the bigger spring is not working in your setup...

 

One of your return springs is not even hooked up. Hook up both thru a hole.

 

Thank you all guys, now I have some things to do this weekend

bad thing is that weather forecast tells me rain for the next days, so I will not have test drive weather

I will try to check all things you recommended me to do, thanks very much for all ideas.

I hope Monday will be dry weather, maybe then first test with my baby