The new Chevrolet
is a car very much larger and more powerful than any model turned
out under the Chevrolet name in recent
years.
It has a wheelbase of 120 in. and is equipped with a 3 3/8 by
4 in. engine, which gives a piston displacement of 286.3 cu. In.
Equipped with
either a four or five passenger body, the car sells at $1,385.
In many respects the
engine design follows previous Chevrolet practice.
Overhead valvesoperated by tappet rods and rock levers are
used, and lubrication is by splash.
The engine is of the
high-speed type, running up to 2400 rpm.
Each set of four cylinders, together with one half of the
upper part of the crankcase, is cast in a block, but the cylinder
heads of each set of cylinders are separate castings secured to the
cylinder blocks by two bolts on the inside of the V and four bolts
on the outside; one-half of the crankcase being cast integral with
the cylinders, the crankcase is divided in a vertical plane.
The valves have a
diameter of 1 ½ in. and a lift of ¼ in.
They are arranged all in a line on top of the cylinder heads.
Their rock levers are mounted on rock shafts carried in
brackets on the cylinder heads.
Between the two rock levers of each cylinder there is a
spacer on the shaft, and between the rock levers of adjacent
cylinders, a coiled spring is placed, the object being to take up
all slack and obviate rattling.
The valve mechanism on top of the cylinders is inclosed by a
pressed steel housing which is held in position by means of two
studs and nuts. A single
camshaft, directly above the crankshaft, operates all valves; it is
mounted in three bearings.
The pistons are
conventional design, gray iron castings and provided with
compression rings at the upper end.
The connecting-rods are drop forged on carbon steel and heat
treated. They are provided
with bronze bushings at the small end and with bronze-backed babbitt
busing at the big end.
Connecting-rods of
oppositely located cylinders are mounted on the crank pins side by
side, the two-cylinder blocks being staggered.
The crankshaft has
three main bearings. The main
bearings are of the same type as the connecting-rod big end
bearings. The lubricating
system is of the circulating splash type.
The oil is circulated by a plunger pump on the right side of
the engine. The plunger of
this pump extends through the crankcase and is operated by an
eccentric on the camshaft.
The pump forces the oil through a distributor pipe inside the
crankcase with outlets to individual troughs.
Under the connecting-rod heads, a branch lead from the pump
is carried up to the instrument board, where it connects to an oil
pressure gage.
An interesting method
is used for lubricating the valve mechanism on top of the cylinders.
The inclosure of this mechanism is not oil tight, hence it is
impossible to operate it in an oil bath, yet it is essential that it
be furnished with a constant supply of lubricant.
This is accomplished by means of an oil pad soaked full of
oil which is placed over the rock levers and held in place by the
valve cover.
Gasoline is carried in
a rear tank of 20 gal. capacity which is provided with a gasoline
gage. Gasoline feed is
affected by a Stewart vacuum system.
A double Zenith carburetor is used, comprising a single float
chamber with individual jets and venturis for each set of cylinders.
The intake pipe, which is in the form of a T, is
water-jacketed aluminum. Hot
air is taken into the carburetor through an air heating stove around
the exhaust pipe of the right hand set of cylinders.
Both the inlet manifold and the exhaust manifold are cast in
the cylinder heads, so there is only one inlet connection and one
exhaust connection to each of the cylinder sets, the former being at
the middle of the cylinder heard at the inside and the latter at the
rear end on the outside.
The starter and
lighting system is of the two unit type and of Auto-Lite make.
Both the generator and the starter are located in the V of
the engine, the former at a forward and the latter at the rear end.
The generator is driven off the camshaft gear, and it has the
radiator fan mounted up through positive gearing, but it is held on
its shaft by means of a friction clutch which will allow it to slip
slightly in case of sudden changes in engine speed.
The starter drive is through a Bendix drive.
A six-volt 120-ampere-hour Willard storage battery is
carried.
The cooling water is
positively circulated by a centrifugal pump.
Contrary to conventional practice, this pump is located in
the line between the jacket outlet and the radiator.
The reason for thus placing the pump was to make it as
accessible as possible and at the same time facilitate the drive.
The pump is driven from the engine crankshaft by a
trapezoidal belt. There is a
double inlet to the pump, one from each cylinder block, and a single
outlet to the top tank of the radiator.
From the lower tank of the radiator there are hose
connections to each of the cylinder blocks.
The radiator is of hexagonal cellular type and has a separate
drawn steel housing. Its fill
cap is covered with a hard rubber composition.
The engine is supported
on the main frame by means of a three point support.
The supporting means are quite unusual and are a development
of the design used on the four-cylinder Chevrolet.
The clutch is of the leather-faced cone type and is provided
with 10 auxiliary springs under the leather.
A feature of the clutch assembly is a self-lubricating clutch
collar. The transmission is
of the three-speed selective type and is operated by a central
control lever, which is of the ball-mounted, ball-ended type.
On the right side of the transmission is an air pump which is
driven through spur gearing from the clutch shaft with two universal
joints. This feature is
somewhat unusual, as the ordinary practice where two universals are
used is to have the propeller shaft exposed.
To make it possible to inclose the shaft, each of the two
universals is surrounded by a spherical joint which is filled with
grease for the lubrication of the universal.
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