My Last Vacuum Leak?, Throttle Body butterfly shaft -VIDEO Options

[ctc911ctc]

914-2L, '74 all original

While I was working on an injector problem, I installed a professionally rebuilt distributor and set the dwell angle right on the numbers: 48 degrees. After correcting the injector trouble I moved on to setting the timing. With the 27Deg RED mark only on the rear side of the flywheel I had to draw a mark on the _other_ side so I could get this done with the timing light, etc. Why do they think of a million other things and not think about marking the fly wheel on both sides?

I believe that I was about 20+ degrees off, after getting it correct, all of the engine missing just went away. I may be at the end of this journey with this car, drove all day, not a flinch, just worked properly. Like my 2 year old 1.7 in 1973.......ahhhh.... (IMG:style_emoticons/default/driving.gif) (IMG:style_emoticons/default/cool.gif)

HOWEVER

I then noticed that the idle was too high, around 1800. I set the idle screw and it is in all of the way - still around 1800. VACUUM LEAK!?! (IMG:style_emoticons/default/mad.gif)

On this car I have had perhaps a dozen different vacuum leaks, manifold gasket (did not seat right), Plenum (needed a complete re-weld), Manifold tube cloth connectors to the plenum (too lose, needed to be snugged a bit closer to the plenum). So, where is this leak?

I recently purchased a smoke machine and was using it incorrectly - I thought that I would see the smoke being SUCKED into the vacuum leak.......well, that did not work, then I wanted a few videos and put the smoke in the throttle body and This is what happened:

https://youtube.com/shorts/rAf5c66Zow4?si=y3TRgC0EJgBFMfmX

Apologies for the bad video, but it seems that the throttle plate shaft in the throttle body is very leaky, any ideas if this is something that could keep the idle high?
Also, note that in the video you can see that I plugged (blue plug) the vacuum valve with the heater in it. does not change the idle very much when plugged - perhaps 200 rpm reduction.

Any ideas as to the shaft leaks and how tight that part of the vacuum circuit it should be?

thank you teeners

[emerygt350]

That's way too much added rpm for the tb bushings. although it is pouring out the TPS side.

Have you put a thumb over the idle screw inlet inside the throttle bore. Sometimes the screw just doesn't seal anymore and that can add a couple hundred rpm. Even with that plus the throttle bushing issue you are too high by a long shot. Remember, a hole the size of the aar inner bore gets you 500 rpm. That's about an 8mm hole.

First, disconnect each vacuum hose from the plenum and plug the port. Same with the retard port on the carb. Then go one by one reattaching them and see what effect it has.

Also, if you are timing it correctly with the hose plugged to the dizzy and then attaching your retard line to the advance side of the dizzy you will be immediately adding 10 degrees to your timing and that will definitely get you a very high idle.

With an idle that high, if it is a leak, you will hear it. I can hear my aar sucking when it is open. Unless it's death by a thousand pin pricks, which is possible. You may want to grab a bottle of carb cleaner and shoot some spots since the smoke looks like a little bit of a disaster.


And now that I think about it... What kind of PCv do you have? If it's the active one make sure you plug it, that is a huge vacuum leak if the valve isn't original or working correctly.