Installing a 37F Supercharger

This is a repro of a 1937 article on installing the McCulloch Supercharger that appeared in the March 1937 issue of Motor Service.

Fig. 1. Supercharger installed on a Ford V-8

The advantages of supercharging have been known for years but the cost has been prohibitive. For this reason, supercharging has been employed only on airplanes, race cars, and a few stock cars but has not been generally available, for the cost of a special installation might almost exceed the value of the car. Now, however, a standard supercharger for the Ford V-8 has been designed and is being placed on the market by the McCulloch Engineering Co., maker of motors for midget racing cars.

Although moderate in price, this supercharger makes a wonderful difference in the power developed by the Ford motor. At 2,000 r.p.m. it raises the power from 60 to 70 h.p. At 3,000 r.p.m. it raises it from 84 to 110 h.p. and at 4,000 r.p.m., from 88 to 123 h.p. Some saving in gasoline is possible although the average user prefers to have the advantage of increased performance rather than economy.

Where Greater Power is Effective

The off-hand opinion may be that the Ford car is powerful enough as it is. While this true as far as top speed is concerned, the additional power does not need to be used for this purpose. For example, when cruising at any speed between 40 and 70 m.p.h, the average driver may find that the greatest advantage is in acceleration which enables him to pass the car ahead before he is endangered by traffic coming in the other direction. At the higher speeds, this acceleration is most needed, and yet is difficult to get, where atmospheric air is depended upon to fill up the cylinders.

While the first demand for these superchargers may be with operators of passenger cars, there is the additional angle that, in truck service, the supercharger will be especially advantageous, making it possible to haul heavier loads at higher speeds, the power being most useful on steep grades. In mountainous districts, for example, when power is most needed, the reduction in atmospheric pressure actually lowers the power of the average motor. A supercharger on the other hand fills a great need where the atmosphere is somewhat rarefied. This was shown in a demonstration race in the vicinity of Denver, Colorado, where a speed of 100 m.p.h. was obtained by Mary Keller of the Gallatin & Verlinden Motors of Denver.

An indirect advantage of supercharging is that the rotor which operates at six times crankshaft speed serves to break up the gas mixture and distribute it more uniformly. This is also said to account for the greater economy which a supercharger can provide.

Generator Moved When Supercharger Is Installed

The installation of the McCulloch supercharger on a Ford V-8 is shown in Fig. 1 in which it will be seen that the generator has been moved to a special position and that the water is carried into jackets which surround the rotor chamber.

Fig.2. Complete supercharger assembly surrounded by major parts of the assembly. (a) Rotor housing. (b) Rotor, (c) Vertical shaft, (d) Worm and gear, (e) New air cleaner, (f) Horizontal shaft, (g) Intake extension, (h) Carburetor gaskets, (j) Special bolts and above them the automatic belt tightener, (k) Special water pumps

Fig. 2 shows a completely assembled supercharger surrounded by the major parts which include two special high pressure water pumps that are used to replace the conventional pump. There is also a shallower air cleaner which is required because of the increased height that results from the use of the supercharger. Fig.2 at the right shows an automatic belt tightener which ensures just the right tension to the belts that drive the supercharger.

Fig. 3. Cut-away view showing vertical shaft which drives rotor.

Fig. 4. Another cut-away view. (a) water jacket; (b) fuel passage; (c) rotor.

Fig. 3 shows a sectional view in which the worm drive can be seen. The rotor is on the top of this shaft. Fig. 4 is another sectional view which shows the rotor and also two passages in the rotor housing. The upper passage is the water jacket while the lower one is the passage through which the fuel mixture is driven. Water jacketing keeps the mixture warm and gives better operation at low speeds.

Special Gearing Used

Fig. 5. This cut-away view shows ball bearing at left of horizontal shaft also long lead-impregnated bronze bearing supporting worm wheel.

Fig. 5 is another sectional view showing the gear of the worm drive. This is actually a special type of gearing known as a Cone gear drive. The horizontal shaft in Fig. 5 has a ball bearing at one end while at the other end is a bronze bearing which is lead impregnated. Eighteen months of development have resulted in the selection of the best possible construction for a supercharger of this character. The supercharger is lubricated by oil under pressure from the engine oiling system, the excess oil draining off through an outlet shown at the lower left of Fig. 5. When assembled, this outlet connects with a hole leading back to the valve chamber.

Installation Procedure

The installation of one of these superchargers is illustrated in the following figures.

Fig. 6. Removing generator and fan , one of the first steps in making the supercharger installation.

Fig. 7. Taking off the carburettor and air cleaner.

Fig. 6  shows that the wiring conduit has been laid to one side, the hood rods are disconnected and the man on the job is just removing the generator and fan. In Fig. 7, he is taking off the carburettor and air cleaner assemblies.

Fig. 8. Removing the combination intake manifold and valve cover.

Fig. 9. New pulleys and water pumps have been installed. Three V-belts provide the drive.

Fig. 8 shows removal of the combination intake manifold and valve cover with which all shopmen are familiar while in Fig, 9 we get the first step in the new installation. It will be seen that a new three-groove pulley has been installed on the crankshaft and that the high pressure water pumps have also been installed, these likewise being provided with three-groove pulleys. The assembler on the job is holding up the belts to the approximate position in which they will be when the supercharger is in place.

Fig. 10. Special gaskets are used when assembling supercharger to the intake manifold.

Fig. 11. Dropping the supercharger into position.

The next step is to install the supercharger unit on the intake manifold and valve cover casting. Here a couple of spacing gaskets are needed as shown in Fig, 10, the man on the job just being in the act of laying these gaskets in place. Fig. 11 shows the next step in the assembly procedure in which the generator drive belt has been put in place and the supercharger is being assembled to the manifold. In addition to the manifold bolts, there is a heavy cap screw at the front which is put in position as the unit is assembled.

Fig. 12. Working supercharger and intake manifold assembly forward in under the V-belts.

Fig. 13. Replacing the fan.

In Fig. 12 we come to the application of the manifold and the supercharging unit to the engine. The front end is lowered and worked in under the belts and then the manifold is slid forward into place. Note that the oil drain previously mentioned is now connected up to the valve chamber by means of a piece of flexible Duprene tubing which goes into a hole which has been bored in the manifold. Fig. 13 shows the supercharger in place and the operator replacing the fan.

Fig 14. Mounting carburettor on top of supercharger

Fig. 15. A special mounting bracket is used for the generator.

Note that an extra belt sticks out to the place where the generator will now be installed. Fig. 14 shows the application of the carburettor while Fig. 15 shows a special bracket which is put on two of the cylinder head studs to provide a mounting for the generator.

Fig. 16. The generator is in its new position and the mounting bolt is being tightened.

Fig. 17. Nearly ready to go out for a spin tightening one of the clamps on the water hose.

In Fig. 16 the generator is in place and the generator mounting bolt is being tightened. Fig. 17 shows a last minute job, the tightening of one of the clamps on the hose which carries hot water to the jacket around the rotor housing.