New Engine Stalling

[travelingman]

I have just finished reconditioning a 1962 Cadillac Sedan Deville which included an engine overhaul, Whilst the engine runs well if you ever need to hard brake I loose vacuum pressure and engine stalls at the end of the the braking.

It is my belief that the nudge actuator (that is what we are calling it) a vacuum disk that is behind the accelerator linkage and connected to vacuum may be faulty. I have checked all the manuals I have a nd can find no reference to this?

Can anyone confirm this is the purpose of this vacuum part? If so, how do I tell if it is working?

Many thanks
Travelingman


Paul David

[Otto Skorzeny]

Are you talking about the anti-stall dashpot? If so, make sure it's working properly and adjust it according to the shop manual. New ones are available for your car if it's defective.

Be sure the carburetor idle speed and mixture adjustments have been set properly before adjusting the dashpot. If the engine stalls after a rapid acceleration and sudden stop, adjust the dashpot plunger so that the clearance between it andthe throttle linkage is reduced.

[Glen]

Hi Paul,

It looks like you are on the right track. 

The operation of the dash pot works like this:  When the engine is running at idle the dashpot should be retracted all the way.  When the engine is under load the vacuum in the manifold drops and the dashpot should extend.  If the throttle is suddenly closed the linkage is stopped by the extended dashpot before the throttle closes.  As the vacuum in the manifold increases the dashpot retracts.  IIRC the dashpot does not have enough power to open the throttle if vacuum drops while the throttle is closed. 

Hope that helps
Glen

[travelingman]

Thank you both, it at least confirms my suspicions though a search of the manual turns nothing up about a dashpot or anthing like it. What I guess I need if either of you can assist is hot to adjust this to see if it working or where to purchase new dashpot from?

Pushing my luck maybe but it has been a great start.

[Otto Skorzeny]

To test the dashpot, disconnect the vacuum line and push the plunger all the way in.

With your finger over the vacuum inlet, release the plunger. It should stay retracted until you move your finger off the inlet.

When the plunger slides back out it should come all the way and do so smoothly. If the plunger doesn't slide in and out smoothly and won't stay retracted when the vacuum tube is blocked, it's defective.

Try suppliers like USA parts or Rock Auto http://www.rockauto.com/ to buy a new one. You may be surprised at the number of parts you can buy at your local auto supply chain. CarQuest and NAPA seem to be the most knowledgeable in my area but even Advance Auto and Auto Zone often carry new parts for my '56.

To adjust the dashpot:
1. As stated earlier, make sure the idle speed and mixture adjustments have been made on the carb and get the engine at operating temperature.
2. Depress the plunger as far as possible with a screw driver and measure the clearance between the plunger and the contact point on the throttle.
3. Adjust the clearance by loosening the locknut and turn the dashpot assembly in or out of its bracket to get the required clearance. Tighten the nut when finished.

To check for correct adjustment:
1. Test drive the car making a fast start. Release the accelerator suddenly and hit the brakes at the same time.
2.The engine should not remain at high rpm, nor should it stall.
3. If it stalls, adjust the dashpot to reduce the clearance between the plunger and throttle linkage.
4. If the engine surges, increase the clearance.

[quadfins]

Look in your shop manual under the Fuel and Exhaust chapter. In 1961, it is on page 10-8, including diagram. Sections 17 and 19d. 1962 should be in the same general location. If you don't have a shop manual, let us know your address, and I can send you copies of the pages.

Jim

[travelingman]

Will look tonight, many thanks