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Classic/Antique Car Repair/Can i do it , or how do i do it ?????

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Expert: - 7/10/2011


Question
My thermostatic vacuum switch is broken on my 1969 Grand Prix, and I can't find a new one. So my question is can I and how do I do away with it.

Answer
The thermostatic vacuum switch was part of the early emissions controls. It controlled the vacuum to the distributor vacuum advance to provide full vacuum during cold operation to battle stalling and the then limited vacuum when warm to try to control emissions. It also sent full vacuum to the distributor vacuum advance to try to prevent overheating at idle. This engine will run very nicely if the valve is bypassed and full vacuum run to the vacuum advance. However I could be fined $10,000 for emissions tampering if I suggested that you do this. Remember when setting the timing after you have done this, to disconnect the vacuum from the distributor when aligning the timing marks and reconnect after the distributor is locked down. It is possible that the idle will be a little lumpy after you do this. If that bothers you find a port on the carburetor that will have vacuum when the engine is running over an idle but has no vacuum at idle. this is called "ported vacuum" and connect the distributor vacuum advance to that port. However if you go this route watch the engine temperature at idle when hot.  

Classic/Antique Car Repair

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Brad Sears

Expertise

All automotive including antique and collectible. However if the car has been modified I can only answer in general terms and maybe get you pointed in the right direction.

Experience

Automotive tech instructor. Syndicated auto columnist 1970's though the early 1990's. Syndicated auto radio talk show, Ask Brad About cars, CBS Radio 70's through 90's TV Show "Last Chance Garage" 1980's PBS-TV syndicated. Auto instructor for the following companies: Fram Autolyte Holly Carter AMF Ford Motor University Of Conn Blue Hills Technical School Sugar River Technical Center Grew up in a family garage in Needham Mass and turned wrenches from the age of 14.

Publications
Manchester Union Leader, Nashua Telegraph, Motor Service Magazine, Yankee Magazine, Popular Mechanics (Saturday Mechanic early 80's), Los Angeles Times, New York Times, and lots more.

Education/Credentials
More than I care to remember. Basically Franklin Technical Institute in Boston, Northeastern University, Fitchburg State Teachers College, Tufts University, and a lot of factory schools along the way.

Awards and Honors
Moto Award winner. And much more.

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