Fig. 31. Stromberg Carburetor—Throttle Wide Open
It will be remembered that at this position of the throttle the accelerating well has emptied, and therefore there is a direct passage for air from the bleeder to the gasoline in the main passage giving the air bleed jet feature explained before. This is being mentioned again in order to call attention to the fact that care should be taken not to use too large a bleeder, because the air which enters through the bleeder partly determines the mixture, and if the bleeder hole is too large the mixture is very apt to be too lean at high speeds.
[Fig. 32] shows an exterior photograph of one of the type M Stromberg carburetor. Before discussing the installation and adjusting of this carburetor it will be well to say a few words concerning the use of the venturi tube and its construction.
The object in using the venturi tube in carburetor design is to produce a maximum air velocity at the jet and at the same time not cause undue restriction. This high air velocity creates the suction necessary to properly atomize the gasoline. The use of the double venturi tube construction has developed the best possible results. In this construction the mouth of the smaller venturi tube is located at the throat of the larger one, and with this arrangement the highest degree of atomization is attainable, and at the same time the air restriction is held down to a minimum.
In order that any carburetor may do justice to what is claimed for it, it is absolutely essential that the motor on which it is installed is in good condition in other respects because, besides poor carburetion, there are numerous things about an internal combustion engine which will cause its poor operation. Therefore, assuming that the following conditions exist, we can proceed with the installation of the carburetor and after adjusting it we can expect very good results as to the operation of the motor.
1. The ignition should be properly timed so that with a retarded spark the explosion takes place when the piston of the cylinder in which the explosion occurs is at its upper dead center.
2. The inlet and exhaust valves should be so timed that they open and close at the proper time during the cycle. In this respect a motor is usually timed when it comes from the manufacturer.
3. The valves should be ground in so that they form a perfect seal with the valve seat. Any accumulation of carbon on the upper part of the exhaust should be removed so as to prevent the valve stem from sticking in the guide and thereby not permitting the valve to close upon its seat.
4. Any undue wear of the valve stem guides should be corrected because the clearance between the stem and the walls of the guide will permit air to be drawn up into the motor thus ruining the mixture from the carburetor. Similarly any leaky flange at any joint along the intake system will produce the same detrimental result.