Stewart Vacuum

[Otahuhu]

On a 1929 Model M Stutz that has been fitted with a Stewart Vacuum tank with the vacuum feed taken off the vacuum pump located below the oil pump, if the motor was allowed to idle for a long period of time will  the motor die off due to the lack of petrol? 

Was the vacuum pump designed to give off the right amount of vacuum at road operating speeds only and not at idle speed? Regards Len 

[John_Mereness]

I would say you have a vacuum tank leak or perhaps a worn pump piston (I assume it is like a 1930/1931 Cadillac and has a miniature piston driven pump that drives off the cam and my understanding it is more for priming purposes than for driving at speed) - if a vacuum leak perhaps at speed you have more vacuum so it tends to keep the tank full and at idle you may not have enough vacuum to keep up (and on hillclimbs you probably have fault as well).   Also, I have always used a cork gasket (impregnated with fuel resistant material) for the tank top and serious drivers have told me to stay away from paper gaskets on the tank top.  You can do leak testing with sudsy / soaped water and a solder brush (every fitting and all the way back to the tank).  You could also have bad pick-up tube in the tank or even a crack in one of the lines or a fitting solder joint.

 

As a sidenote:  A fully primed vacuum tank should run the car just fine without assist of the piston pump off the cam (most cars just had the tank and did not have the auxiliary pump off cam).

 

Add'l sidenote:  If the tank has a shut off you should be using it for any stop longer than a few hours or overnight - it will help keep the tank primed

 

Also, a vacuum tank system also fails via rust chips in a lines, clogged screens, bad springs, leaky float, sticking float, shut off valve not fully open at speed, and .....  matched to such as vapor lock in lines from heat and .....

[stutzl6]

Stutz l;6 the vacuum tank for Stutz m 1929-30 is a oil vac tank not a stewart  they are hard to find . oil vac tank can not be used for vacuum from the manifold because it does not shut the vacuum off when full like a stewart tank. this become a vacuum leak. the steward should work.  do you have the vanes in wrong . this will have enough vacuum at low speed and you will run out at 35 mph. Iam using and oil vac  on 1929 backhawk this may the only car running on the oil vac set up. thank john