VCCA Home Forums GENERAL DISCUSSION New User Forum VACUUM TANK (stewart)

On my 1928 tourer 2.8 I am trying to find out how high the float should be in the upper chamber in the vacuum tank.Every time I check mine after running the engine it is very low on the bottom of the chamber.I use a small rod through the top priming bolt hole can any one help

For better coverage, you also might want to post your question in the 1912-1928 forum.

First, Which Stewart vacuum tank do you have?

According to the 1927 - 1928 Chevrolet Repair Manual the standard one for the 1928 AB National and the 27 AA National, which is either a 493 A for AA Capitol open cars and trucks, or a 493 C for the AB Nationl. I Identify the 493 by the number of bolts on top and the configuration of the suction and Fuel intake lines but the main difference is inside the tanks, the 493 is much simpler inside, than the large tank model, with a bell shaped float with a stem that will close the atmospheric valve in the Center valve assembly when the float drops. The clearance should be (.018" to .028") when the float is at the lowest point of travel.
The clearance for the flapper valve on the bottom of the inner tank should be.022" - .028", if it is less than 0.22 the passage of the gasoline from the inner tank will be slow, if the opening from the flapper valve is greater than 0.28" the suction may not be great enough to close the flapper valve, the inner tank will not pump gasoline and the carburetor will starve. Quoted from the 1927-1928 Repair manual.
I know it may be diffucult from the UK, but I would suggest that you purchase a set of Chevrolet Service news and a 1927-1928 Chevrolet Repair Manual. I bought mine Repair Manual from Gary Wallace and Service News from The Filling Station, which runs advertisments on this site.

If you have the correct vacuum tank and correct interior float, the problem is likely that the float is not properly installed. There is a rod coming out the top of the bell shaped that has a semi-circular bend just above the float a straight section then another semi-circular bend at the top ending in a ~1/2" straight leg. The upper bend needs to be completely inserted into the loops on the valve rods so they ride in the straight section. The "leg" keeps the float from rotating. It is the length of the straight section between bends that determines the lowest and highest fuel levels in the tank.

I now have a repair manual and a new gasket for the top, I think my one is 493c it has 8 screws holding the top on.Looking at the drawing the float is high in the top chamber, cannot wait to have it running wright.

I thought I had I must of not done it right. I am still new to this, with pratice I will get it right.