The New Buick Aluminum Engine
| by: | J.D. Turlay, E.H. Holtzkemper, and C.G. Studaker |
| Buick Motor Division General Motors Corporation Flint, Michigan |
re-published by permission in BritishV8 Magazine, Volume XVI Issue 2, October 2008
INTRODUCTION
The introduction of the new Special for 1961 was the result of a
re-evaluation of the traditional Buick position in the overall car
market. With this new concept of a smaller, fine car came the opportunity
for the Engineering Department to start with a "clean sheet of paper",
not encumbered with the requirements of utilizing existing tooling or
components.
It was recognized early that to make the necessary gains in fuel economy
so important to the customer and yet maintain a level of performance
acceptable to the discriminating car buyer, weight would be a critical
factor. The decision to design an engine around major aluminum castings
was the outgrowth of this realization, due not only to its direct effect
upon overall car weight, but also it's effect upon the weight of other
chassis components. By taking advantage of this overall weight reduction,
engine displacement could be held at a minimum for a given level of
performance with consequent advantage in both manufacturing and operating
economies.
The application of aluminum in engine design is far from new and the
majority of engines on the market today have utilized this material
in some form for many years. An aluminum hi-performance V-8 engine was
designed and built at Buick to power the famous XP-300 and LeSabre
experimental cars of the early 1950's (Figure 1). The new Special engine,
however, is the first mass produced aluminum V-8 engine to be used in an
American-built passenger car.
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| Figure 1 EXPERIMENTAL XP-300 ALUMINUM ENGINE |
Figure 2 EVOLUTION OF ALUMINUM IN BUICK V-8 ENGINE |
Recognizing the advantage of aluminum in making possible both weight and
cost savings, a gradual evolution has been taking place at Buick since
the introduction of the present line of cast iron V-8 engines in 1953
(Figure 2). Aluminum pistons, rocker arm shaft brackets and oil filter
base were incorporated in the original design. The water pump cover,
water manifold, water outlet and timing chain cover were designed for
die casting in aluminum; however, economic considerations did not permit
their adoption at that time. All, except the water manifold, have since
been re-evaluated as aluminum die castings and released for production:
the water outlet in 1955, the water pump cover in 1957, and the timing
chain cover in 1958. In addition, the 1961 large Buick engines include
die cast rocker arms, water pump impeller, generator end frames, generator
bracket, fan spacer, fuel pump dome and body to further supplement the
conversion to lightweight aluminum castings. The experience gained through
the use of the above parts, especially those exposed to the coolant, gave
us the necessary background to embark on a program of extending the use
of aluminum to the major castings of the Special engine: namely, the
cylinder block, cylinder heads and intake manifold.
In addition to the above experience, we have drawn heavily on the
background of knowledge in the use of aluminum for major engine components
available from the Power Development Section of the Engineering Staff
Division, General Motors Technical Center. They have been engaged in
extensive research and development in this field since 1951 and their
assistance has been invaluable. Prototype engines for this program
originated with them, with Buick assisting by serving as prime supplier
to gain further experience. The production design was started at Buick
in December of 1958 and much of the experience obtained from the
prototype program applied directly to the engine being covered by
this paper.
There has been much discussion regarding the corrosion characteristics
of aluminum when used in critical locations connected with the engine
cooling system. Our experience with the water pump cover, timing chain
cover and water outlet has shown that with proper care in the selection
of the alloy used, in meeting the design requirements, and in careful
manufacturing control, corrosion does not become a field problem. All
of these parts are cast of GM-4097M alloy containing 11.0 to 13.0
percent, silicon and less than one percent copper for excellent corrosion
resistance.
GENERAL DESCRIPTION
An eight cylinder V-8 engine was chosen to power the new Buick Special due
to its inherent advantages:
1. Small package size.
2. Smoothness of operation.
3. Rigid construction.
4. Excellent output characteristics and
5. Light weight.
It was felt that no compromise in any of the foregoing could be tolerated
and still produce a vehicle of the quality desired by our customers.
In view of the projected overall car weight of approximately 2700 pounds,
a displacement of 215 cubic inches was chosen to provide for excellent
economy characteristics while giving the driver the nimbleness he has come
to expect in an American-built automobile. This displacement was obtained
with a bore of 3.500" and a stroke of 2.800" for a stroke-bore ratio of
0.8, the same as the original 322 cubic inch Buick V8 engine.
The overall engine compactness is readily apparent from a cross section of
the engine (Figure 3) which clearly shows the functional use of all available
space within the engine outline. Exhaust manifolds are neatly tucked in along
the cylinder banks to reduce the overall engine width. The intake manifold is
recessed in the "V" of the cylinder heads as close to the curved lifter
compartment cover as possible to reduce overall engine height.
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| Figure 3 TRANSVERSE CROSS-SECTION OF BUICK ALUMINUM V-8 |
Figure 4 ALUMINUM COMPONENTS OF 215 ENGINE |
Aluminum castings were utilized wherever possible (Figure 4) in the interest
of maximizing weight saving. The cylinder block and cylinder heads are made
by the semi-permanent mold process due to the necessity for sand water jacket
and port cores. The intake manifold is made as a sand casting. Die castings
include such components as: timing chain cover, water pump cover, water pump
impeller, water outlet, flywheel housing, oil pump cover, rocker arms, rocker
arm shaft brackets, distributor body, starter and generator end frames,
carburetor throttle body, and oil pressure indicator switch housing. The
pistons, as in most automotive engines in use today, continue as full permanent
mold castings.
All other engine components were carefully scrutinized to obtain a design
providing for minimum weight while maintaining a high level of durability
and structural rigidity.
The final result of this weight-conscious approach to the design of the new
Special engine is a total dry weight of 324 pounds or 1.50 pounds per cubic
inch displacement (Figure 5). A comparison with several 1960 American-built
compact car engines reveals that this weight per cubic inch ratio is far
superior and is the only one with a value under two pounds per cubic inch
displacement. As an additional measure of the benefits of this concentrated
attack on the weight problem, a comparison of the performance level in terms
of pounds per horsepower output reveals a figure of 2.09 for this engine as
compared to 3.50 for the nearest competitor.
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| Figure 5 COMPARISON OF WEIGHT PER UNIT DISPLACEMENT |
Figure 6 COMPARISON OF WEIGHT PER HORSEPOWER OUTPUT |
COMBUSTION CHAMBER
The American car buyer is becoming increasingly more critical of car
operating costs and for this reason it was established that the Special
should operate on regular gas. To accomplish this and still provide maximum
utilization of the regular grade fuels available, careful attention was
given the selection of a combustion chamber for the new engine.
The combustion chamber finally chosen was formed by a slanted, elongated
saucer shape in the cylinder head accompanied by a shallow circular depression
in the piston dome (Figure 7). Piston coverage of 15 percent is provided
by a 0.35" wide land around the top of the piston adding to the turbulence
of the swirling fuel-air mixture leaving the slightly offset inlet port.
The spark plug is centrally located, being only 0.404 inches from the
cylinder centerline (Figure 8) which results in a short, uniform flame
travel to all parts of the chamber.
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| Figure 7 COMBUSTION CHAMBER |
Figure 8 SPARK PLUG LOCATION |
The new design combines the low surface-to-volume ratio advantage of the hemispherical chamber with the turbulence of the wedge-type chamber for excellent mechanical octane characteristics. This permits operation with deposits at a compression ratio of 8.8 to 1 on 92 Research octane fuel without trace knock. In addition, this chamber includes an in-line valve arrangement with minimum shrouding of both inlet and exhaust valves providing a high degree of breathing efficiency.
SERVICE
Serviceability was of prime importance in the overall engine arrangement
and resulted in several interesting features. The ignition distributor is
located in the timing chain cover at the front of the engine (Figure 9)
eliminating the need for the average mechanic to double as a contortionist
for even a simple point adjustment. The timing indicator, being cast
integral as a part of the timing chain cover (Figure 10) is conveniently
located in close proximately to the distributor, permitting the mechanic
to accurately adjust the distributor and observe the timing point from
the same position.
Spark plugs are all easily accessible (Figure 11) even with a full
complement of accessories - including power steering and air conditioning.
All cylinder head bolts may be reached with the rocker arm covers removed
without disturbing the exhaust manifolds, also adding to the convenience
of the Service Department should head removal ever be required.
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| Figure 9 RIGHT FRONT VIEW OF ENGINE |
Figure 10 IGNITION TIMING INDICATOR |
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| Figure 11 ASSEMBLED CYLINDER HEAD |
Figure 12 ENGINE COOLING SYSTEM |
COOLING SYSTEM
A straight-through type cooling system is employed with the cylinder heads
being in series with the cylinder block on their respective banks (Figure 12).
Water enters the pump through a passage in the die cast water pump cover and
passes through three holes near the hub of the six-vane die cast impeller.
The rim of the impeller serves as a seal between the inlet and outlet sides
of the water pump while a cast cavity in the front of the timing chain cover
forms the rear surface of the pump. This construction permits the die casting
of both the water pump and the timing chain covers and provides an efficient,
low-cost water pump.
From the outlet side of the pump, the water divides uniformly and enters the
cylinder block through openings in front of each cylinder bank. After passing
around the cylinder walls to the rear of the block, the flow is directed
through passages in the top deck to the rear of the cylinder heads. From
here the coolant travels forward through the head to an outlet at the front
on the intake manifold mounting surface. At this point the water proceeds
under the manifold proper to the rear and hence to the top of the manifold,
forward around the carburetor mounting flange to the thermostat housing
cavity, cast integral with the manifold.
The thermostat by-pass is provided by an integrally-cast tube on the water
outlet which registers with a hole drilled into the thermostat cavity of the
intake manifold (Figure 13). A short rubber hose from this tube, in turn,
connects with a similar inlet on the timing chain cover leading to a passage
to the inlet side of the water pump.
Water pump and fan speed ratio is 0.85 to 1 to provide adequate coolant flow
with minimum power requirement and low level of fan noise.
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| Figure 13 THERMOSTAT BY-PASS AND WATER PUMP |
Figure 14 FRONT COVER ASSEMBLY |
LUBRICATION SYSTEM
The lubrication system centers around the front mounted oil pump (Figure 14)
driven directly by the distributor. This necessitates the use of a non-submerged,
external oil pump remote from the sump located near the center of the oil pan.
The oil pump gear cavity is integral with and machined in the timing chain
cover insuring correct alignment between the oil pump driving gear shaft and
the distributor mounting hole (Figure 15). The oil pump cover is a separate
die casting and serves as a mounting for the full flow, throw-away type oil
filter cartridge, eliminating the need for a separate oil filter base. Both
the oil pressure relief valve and the oil filter bypass valve are located in
the pump cover to further consolidate functional components. A 30 mesh screen
is located in series with the oil pressure relief valve to prevent stray
chips and dirt from interfering with the operation of the plunger-type valve.
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| Figure 15 ENGINE OIL PUMP |
Figure 16 ENGINE LUBRICATION |
The oil pump intake is provided by a drilled hole down the right side of the
cylinder block to the center main bearing bulkhead (Figure 16) on which the
intake screen and housing assembly is mounted. A separate screen assembly,
of 24 mesh, is located in the housing with a thin annulus of 0.050" thickness
around the periphery to permit oil to pull over in the event the screen
becomes plugged.
As the incoming oil leaves the cylinder block it proceeds through passages in
the timing chain cover to the pump cavity proper. A standpipe effect is
attained on both the inlet and outlet sides of the pump to insure a sufficient
reservoir of entrapped oil for reprime of the pump in the event the remainder
of the system is drained.
High pressure oil passes from the pump outlet into the pump cover, through the
filter and back into the cover via the steel nipple cast in place for the filter
mounting. Passages in the pump cover and timing chain cover, in turn, direct the
oil to the high pressure galleries in the cylinder block. The oil pressure
indicator light switch is mounted in the oil filter by-pass valve cap since this
hole serves as part of the outlet passage for the high pressure oil to the block.
The high pressure oil distribution system consists of two main oil galleries
drilled the length of the block and intersecting the valve lifter holes for
approximately one-half the gallery diameter. This then supplies the lifters with
oil at line pressure and insures an adequate supply of oil to the lifters at all
times.
Oil is supplied to the main and cam bearings by angled holes drilled from the
top center of the main bearing bores to the right-hand main oil gallery. Connecting
rod bearings are furnished oil in the conventional manner with holes drilled
in the crankshaft.
Full pressure overhead lubrication is supplied by a drilled hole intersecting
the main oil gallery ahead of the front valve lifter boss on each bank. A cast
depression in the base of the symmetrical rocker arm shaft bracket provides
passage for the oil to the mounting bolt hole and thence to the rocker arm shafts
(Figure 17). By taking the overhead oil from a point ahead of all lifters in the
main galleries, a maximum amount of entrained air is bled off ahead of the lifters,
resulting in better lifter performance.
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| Figure 17 OVERHEAD LUBRICATION |
Figure 18 FRONT END LUBRICATION |
Drilled holes are located in the shafts at each rocker arm location and are
rotated toward the push rod ends of the rocker arms away from the high load point
to permit a sufficient quantity of oil to escape for proper lubrication of the
overhead mechanism. Strategically located lubricating grooves are broached in the
rocker arm bores to provide a film of oil which is distributed by the oscillating
action of the rocker arm. The push rod seat end of each rocker arm is supplied an
adequate amount of oil by a hole drilled to the seat end from the rocker arm shaft
bore. The valve tip end is lubricated by controlled oil flow along the rib section
on the side of each rocker arm. A slot located in the rocker arm hub allows this
oil to escape from the chamfer around the inside diameter of the hub and is located
such that only the required portion of oil finds its way across the top of the arm
and thence to the valve tip. Excess oil spills off the backside of the rocker arm
away from the valve tip end. Since this arrangement effectively meters the amount
of oil reaching the valve stems and guides, no auxiliary seals or shields are
required.
Oil for lubricating the distributor gears, fuel pump eccentric, timing chain and
sprockets is supplied in an unusual manner. Leakage oil from the front cam bearing
is trapped by the thrust flange and delivered through a drilled hole to the sprocket
and eccentric keyway (Figure 18). A radial slot on the front side of the eccentric
registers with the keyway and provides an outlet for the oil. In operation, oil is
thrown radially from this slot to the distributor gear which in turn throws the oil
onto the timing chain and fuel pump eccentric. This system lubricates all parts
operating in the front cover without flooding the area, thus reducing the load on
the front crankshaft seal.
The front crankshaft oil seal is of the graphite impregnated rope type held in place
in the front cover by a pressed-in steel retainer. A shelf on the inside of the
timing chain cover reduces the direct flow of runoff oil into the seal area. In
addition, a slinger mounted on the crankshaft extends over a lip on the seal
retainer and effectively reduces the amount of oil reaching the seal proper.
The rear main bearing oil seal is also of the graphite impregnated rope type, but
of necessity, is split with one-half in the cylinder block and the other half in
the rear main bearing cap. A slinger machined on the crankshaft ahead of the seal
area operates in a groove machined in the cylinder block. The slinger groove is
drained by a cast-in slot at the bottom and in addition is vented into the
crankcase section by a hole drilled near the top.
CYLINDER BLOCK
The cylinder block, being the largest individual structural component of the engine, offered the greatest potential weight savings through the use of aluminum (Figure 19). Semi-permanent mold castings were chosen to permit use of conventional sand cores in forming the water jackets and lower crankcase area of the cylinder block. All remaining exterior surfaces of the casting are formed by metal die sections, resulting in an attractive casting appearance and providing excellent physical properties for such critical areas as the cylinder head surfaces.
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| Figure 19 CYLINDER BLOCK |
Figure 20 CYLINDER SLEEVE AND BLOCK ASSEMBLY |
Long a major deterrent to the widespread use of aluminum cylinder blocks
in the automotive industry has been the lack of an economical means of
providing a satisfactory cylinder bore surface. This problem was overcome
by the adoption of cast-in-place iron sleeves (Figure 20) thus eliminating
the costly manufacturing complications of wet liners with their inherent
sealing problems, pressed-in dry sleeves and accompanying increase in expensive
precision machining requirements.
The outside diameter of the centrifugally-cast sleeve is machined with
circumferential grooves having a pitch of 8 per inch and a depth of 0.010".
These grooves form a very effective means for mechanically locking the sleeves
in place.
The cylinder block design incorporates the dropped pan rail (long a Buick engine
feature) having the oil pan mounting surface 2.250 inches below the crankshaft
centerline (Figure 21). This configuration provides flat oil pan mounting surface
and also permits mounting the starter directly in the cylinder block for added
rigidity.
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| Figure 21 FRONT OF CYLINDER BLOCK |
Figure 22 CYLINDER BLOCK FLYWHEEL HOUSING END |
The mounting surface for both the Automatic and Synchromesh transmissions is provided
by the well-ribbed deep-section flywheel housing end of the cylinder block
(Figure 22). The effect of this deep block feature is an increase in the natural
frequency of the engine-transmission assembly in vertical bending which provides
a smoother, more nearly vibration free installation since this is well above the
natural frequency response range of the rest of the vehicle.
Two air inlets are provided in the flywheel housing of the cylinder block for the
Air-Cooled Dual Path transmission. These inlets are covered by the die cast flywheel
and clutch housings when the Synchromesh transmission is specified.
Cast iron main bearing caps are used with the aluminum cylinder block (Figure 23)
and provide effective control of main bearing clearances throughout the operating
range. The difference between the coefficient of expansion of aluminum and cast
iron resulted in a problem in this area during the early stages of the development
program. With the main bearing caps as originally designed (Figure 24), the higher
expansion coefficient rate of the aluminum caused the horizontal clearance of the
bearing to change at a greater rate than the vertical clearance with a change in
temperature. Subsequent redesign of the main bearing caps, increasing the moment
of inertia of the cap cross section by 67 percent, resulted in a significant
reduction in the relative change between the vertical and horizontal bearing
clearances.
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| Figure 23 BOTTOM VIEW OF CYLINDER BLOCK ASSEMBLY |
Figure 24 MAIN BEARING CAP COMPARISON |
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| Figure 25 BOLT LOADING IN ALUMINUM |
Figure 26 CYLINDER BLOCK WATER JACKET DEPTH |
The bolt torque versus clamping load characteristics of aluminum threads presented
an additional problem in the control of main bearing clearances. Repeated assembly
of untreated bolts in the aluminum threads resulted in a substantial reduction in
clamping load for a given bolt torque value (Figure 25). This loss in load caused
a change in main bearing bore diameter between machining and engine assembly since
the bearing caps are removed and reinstalled. An investigation into the merits of
various thread treatments led to the development of a lubricant which gave uniform
loading on the initial bolt installation as well as on reassembly at the same bolt
torque. As a result the cylinder head, rocker arm shaft, and main bearing bolts are
lubricated prior to the initial assembly since all are subjected to high loads and
require uniform performance.
A minimum thread engagement equivalent to twice the bolt diameter was adopted for
all bolts threaded into aluminum to permit utilizing the load carrying capacities
of the respective bolts. There has been no evidence of a loss in bolt loading in
combination with the aluminum threads even after extensive operation of all types.
The depth of the water jacket in the cylinder block is only 4.06 inches as compared
to an overall bore length of 5.56 inches (Figure 26). This results in a reduction
in heat rejected to the cooling water and quicker warm-up while providing adequate
cooling capacity. Only one cored opening through the cylinder head deck from the
water jacket is provided at the rear of each bank resulting in a minimum of openings
for potential cylinder head gasket water leaks (Figure 27). A cylinder head bolt
pattern featuring five (5) bolts per cylinder was adopted due to the excellent
performance of this pattern in our larger cast iron V-8 engines.
A 0.015" thick aluminum-coated steel, beaded cylinder head gasket is used and is
interchangeable between cylinder banks. Double beads are provided around the
cylinder bores for added protection in these critical areas.
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| Figure 27 CYLINDER BLOCK AND HEAD GASKET |
Figure 28 CYLINDER HEAD WATER JACKET AND PORT CORES |
CYLINDER HEAD
The cylinder head is also a semi-permanent mold casting having dry sand water
jacket and port cores. An interesting feature of the cylinder head is the use
of a one-piece water jacket core (Figure 28) eliminating a pasted core sub-assembly
and reducing the number of cores required from the core room. This one-piece
core also results in more accurate control of wall sections and eliminates
undesirable fins in the water jacket area. Port and water jacket cores may be
assembled directly into the die eliminating the need for assembly fixtures.
The water jacket core is designed to eliminate a maximum amount of unnecessary
water while providing excellent cooling for such critical areas as inlet and
exhaust valve seats, exhaust valve guides and spark plug bosses. The one-piece
core design results in a triangular section having good structural strength
characteristics for handling in the foundry.
The elimination of the water jacketing over the inlet ports permits an open
construction on this side of the cylinder head for a lightweight casting. Over
head lubricating oil drains freely through this area to the cylinder block.
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| Figure 29 INLET PORT |
Figure 30 EXHAUST PORT |
Both inlet and exhaust ports (Figures 29 & 30) are streamlined to reduce
to a minimum the resistance to flow of both the incoming fuel-air mixture and
the departing exhaust gases. The exhaust port is kept short to reduce heat
rejected to the cooling water and the elimination of the conventional exhaust
crossover ports further minimizes the cooling requirements.
Valve seat inserts of alloy cast iron are employed and are assembled into the
cylinder head by a shrink fit process. Both valve and seat insert life have been
very good, attributable in part to the excellent thermal conductivity of the
aluminum head and the water jacketing around the valves. Separate, pressed-in-place
alloy iron valve guides are also used to complete the cylinder head assembly.
CRANKSHAFT
The crankshaft is an Arma-steel casting having the counterweight periphery
and cheeks cast to size reducing casting weight and machining required
(Figure 31).
The counterweights are contoured for uniform clearance with the piston skirts,
thus utilizing the most effective room available for counterweighting (Figure 32).
In addition, the counterweights are oriented in the most advantageous plane for
balancing the engine with the minimum amount of material. This design approach
results in a finished crankshaft weighing only 38.4 pounds. The main bearing
journal diameters are 2.300" and the crank pin diameter 2.000", which when
coupled with 1.400" crank throw, results in an overlap of 0.75".
The crankshaft end thrust is taken on a flange bearing at the center main bearing
bulkhead (Figure 33). All main bearings are of steel-backed babbit material with
a groove in the upper insert and plain lower inserts. The elimination of a groove
in the lower insert increases load carrying capacity and also reduces oil pump
flow requirements by effectively reducing leakage oil at the main bearing and
partially metering the oil to the connecting rod bearings.
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| Figure 31 CRANKSHAFT |
Figure 32 POWER TRAIN |
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| Figure 33 LONGITUDINAL CROSS-SECTION OF ENGINE |
Figure 34 PISTON AND CONNECTING ROD ASSEMBLY |
CONNECTING ROD AND PISTON
The connecting rods are made of SAE 1141 forged steel and have a center distance
of 5.660" providing a conservative rod length to stroke ratio of 2.02 (Figure 34).
Weight control is accurately maintained by the milling of weight bosses located
at the connecting rod assembly center of gravity. The connecting rod bearings
are also of steal backed babbit material.
The piston is a one-piece aluminum alloy casting featuring the long-standing
Buick practice of a full skirt, double trans-slot design. Windows are cast
beneath the piston pin bosses to effectively divorce the skirt from the bosses
in this area. Better dimensional control throughout the operating load range is
obtained with this construction since the lower skirt is not as readily affected
by pin boss deflections. This piston, coupled with the 0.875" diameter piston
pin pressed into the connecting rod small end, supplies a rugged structural
starting point for the transmission of mechanical energy to the flywheel.
Two 5/64" compression rings and one 3/16" steel rail oil ring are provided with
the top compression ring and the oil control ring chrome plated.
VALVE TRAIN AND DRIVE
The alloy iron camshaft is driven by a 3/8" pitch chain through a sintered iron
crankshaft sprocket and a cast iron camshaft sprocket (Figure 35). Hydraulic
valve lifters are used with both Synchromesh and Automatic transmission engines.
Push rods are made of 1/4" steel rod, upset and hardened at both ends.
Die cast rocker arms similar to those introduced on the 1960 Buicks are employed
to further extend the application of light metals to this engine. Inserts are
installed at each end of the rocker arm with the ball seat for the push rod being
of sintered iron and the valve-tip pad an upset steel insert.
Inlet valve diameter is 1.500" and the exhaust valve diameter 1.3125". Both
valve stem diameters are basically 0.340 inches with 0.0005 inches taper in the
length of the stem - being smaller it the bottom.
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| Figure 35 VALVE TRAIN AND DRIVE |
Figure 36 INLET MANIFOLD SECTIONS |
INLET MANIFOLD AND CARBURETION
The intake manifold is the only completely sand cast component due to the
complexity of coring in a V-8 manifold (Figure 36) and to the more flexible
nature of the sand casting process.
The branch size of the manifold was made as small as possible, consistent
with good breathing characteristics, to provide a minimum manifold volume
for instant response under changing load conditions.
The intake manifold heat is provided by the water jacket through which all
of the engine coolant flows. This results in a rapid rate of warm-up due to
the excellent thermal conductivity characteristics of the aluminum. Another
important advantage of this method of supplying manifold heat is the uniformity
of temperatures of the mixture supplied to the individual cylinders.
A two barrel carburetor is standard equipment on both Synchromesh and Automatic
transmission engines and incorporates aluminum throttle body which, in
conjunction with a metal carburetor to manifold gasket, provides excellent
heat transfer characteristics. This construction reduces appreciably the
tendency of the throttle valves and idle system to "ice up" under adverse
atmospheric conditions.
FUEL SYSTEM
The fuel pump is mounted low on the loft side of the front cover (Figure 37) and driven by a sintered iron eccentric mounted on the camshaft. A glass bowl, paper cartridge fuel filter is standard on all engines and is mounted near the carburetor to prevent foreign material from entering the critical needle seat or jet areas. Metal lines are used between the carburetor and the fuel pump with metal and rubber lines between the fuel pump and tank.
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| Figure 37 LEFT FRONT VIEW OF ENGINE |
Figure 38 FRONT VIEW OF ENGINE |
EXHAUST MANIFOLDS
The cast iron exhaust manifolds have passages with gradually increasing
cross-sectional areas to minimize resistance to flow of the burned gases.
The right manifold incorporates a heat stove, which in conjunction with a
stainless steel tube running through the manifold proper, supplies heated
air to actuate the carburetor automatic choke. No heat valve with its potential
sticking or rattle problem is used since the intake manifold is water-heated.
A ball-type flange is used at the exhaust manifold to pipe junction, eliminating
the need for a separate gasket and also providing flexibility for proper alignment
of the exhaust system at this point.
ELECTRICAL
The coil is mounted on the intake manifold forward of the carburetor in close proximity to the distributor (Figure 38), resulting in a short high-voltage lead wire for minimum voltage loss. The resistor type spark plug wires are held in place with plastic clips attached to a bracket on each rocker arm cover. Extended reach AC 45FFS spark plugs are used with a thread length of 1/2".
ENGINE VENTILATION
Engine ventilation inlet air is provided by a combination breather and filter cap in the left rocker arm cover. The outlet for crankcase gases is provided by a ventilator pipe in the right rocker arm cover, which extends down into an area below the pan rail near the fore and aft centerline of the engine. A baffle is mounted on two rocker arm shaft brackets beneath the outlet pipe (Figure 39) preventing oil from splashing out the breather pipe and also providing a relatively low velocity area for entrained oil to separate from the departing crankcase gases.
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| Figure 39 TOP VIEW OF ENGINE WITH COVERS REMOVED |
Figure 40 ACCESSORY MOUNTINGS |
ENGINE COVERS
Valve rocker arm covers are of stamped steel, zinc plated for rust resistance and
to further accentuate the appearance of the unpainted aluminum components. Right
and left cover stampings are basically the same with the assemblies modified to
take the ventilator breather cap in the left cover and the ventilator pipe in the
right cover.
The lifter compartment cover is formed by the intake manifold gasket extending
across under the manifold proper and lengthwise to vertical walls at the front
and rear of the cylinder block. Rubber seals are installed between the gasket
and cylinder block at the end walls with a hardened steel clamp installed over
the gasket. The clamp arc is designed to provide a uniform load on the gasket
when torqued to the specified limits.
OIL PAN
The oil pan is also a zinc plated steel stamping with the major sump area located near the fore-and-aft centerline of the engine as dictated by chassis installation requirements.
ACCESSORY MOUNTINGS
The accessory mountings with a new engine design are usually left until
all other components have been completely laid out. Consequently, the engine
designer is concentrating on basic engine problems while the chassis and
sheet metal designers are busy at work laying claim to all available space
surrounding the engine. The end result is a frantic scramble to find
suitable locations for mounting the generator, power steering pump, air
conditioning compressor, etc. However, with engine compartment room at a
premium in this installation, close cooperation between all design sections
involved resulted in the maximum utilization of the space available.
The generator is mounted low on the right-hand side of the engine directly
in the fan blast for improved cooling. The rear end frame is attached
directly to a boss on the exhaust manifold and the front supported by a
simple triangular stamping bolted to the rear cover. An additional tubular
brace is provided between the front pivot point and an end cylinder head
bolt for increased mounting stiffness. A three-point drive is used with a
single belt driving the generator and water pump.
The power steering pump is mounted in front of the left cylinder head
(Figure 40) with the rear bracket bolted to bosses provided on the head
and the front bracket attached to the timing chain cover.
The air conditioning compressor is mounted low on the left side of the
engine with the rear mounting attached directly to the cylinder block.
The front mounting bracket is shared with the power steering pump on
those cars equipped with both, or is a similar but simplified bracket on
non-power steering air conditioned cars.
Both the power steering pump and air conditioning compressor are driven
by a two-point drive with the belts going directly from the crankshaft
pulleys to the individual accessory pulleys. Each accessory is adjustable
to provide for belt tightening.
These accessory mountings, being attached directly to the basic engine
wherever possible, result in a rigid, vibration-free assembly so essential
with the reduced mass of the aluminum engine.
TEST RESULTS
During this development program experimental and initial production engines
underwent over 10,000 hours of various dynamometer testing and 1,000,000 miles
of operation in test cars prior to actual announcement to the public. No major
engine failures occurred throughout this extensive development program attesting
to the durability of this sturdy, yet lightweight engine.
The adequate valve sizes in conjunction with the streamlined ports and manifolds
result in an engine output curve giving excellent mid-range torque while
maintaining a high level of horsepower output at speeds above 4000 R.P.M.
(Figure 41). On a gross output basis, the engine is rated at 220 lb.-ft.
torque at 2400 R.P.M. and 155 horsepower at 4600 R.P.M.
Figure 41
ENGINE OUTPUT - GM TEST NO. 20
OPTIONAL ENGINES
An optional engine including a four barrel carburetor and a compression ratio of 10.25 to 1 is available for those applications requiring an even higher level of performance. This option increases the maximum torque output of the engine to 230 lb.-ft. at 2800 R.P.M. and the horsepower to 185 at 4800 R.P.M., also on a gross output basis.
CONCLUSIONS
As a result of the experience gained during this development program as well as
production experience to date, we feel the following conclusions to be important.
1. A pronounced weight savings has been made through the extensive use of aluminum
in this engine with no loss in engine output or durability.
2. The basic goals of a quiet, durable, yet responsive engine have been attained
by careful design consideration when combining the light weight of aluminum with
the structural and wear characteristics of cast iron in critical areas.
3. Normal care of the cooling system has been found to be entirely adequate in
the control of corrosion in this aluminum engine.
4. Engineering problems connected with an aluminum passenger car engine have been
satisfactorily overcome and the further extension of aluminum to future engines
will be governed primarily by economic considerations.
APPENDIX
GENERAL SPECIFICATIONS
| Bore, In. | 3.50 | |
| Stroke, In. | 2.80 | |
| Displacement, Cu.In. | 215 | |
| Numbering System, Front to Rear | ||
| Left Bank | 1-3-5-7 | |
| Right Bank | 2-4-6-8 | |
| Firing Order | 1-8-4-3-6-5-7-2 | |
| Compression Ratio | 8.8-1 | |
| Crankshaft Main Bearing Diameter, In. | 2.300 | |
| Crankpin Journal Diameter, In. | 2.000 | |
| Connecting Rod Length, Center to Center, In. | 5.66 | |
| Rocker Arm Ratio | 1.6-1 | |
| Type of Lifters | Hydraulic | |
| Valve Spring Load, Lb. | ||
| Valve Closed | 64 | |
| Valve Open | 164 | |
| Valve Lift, In. | ||
| Inlet | 0.383 | |
| Exhaust | 0.383 | |
| Valve Head Diameter, In. | ||
| Inlet | 1.500 | |
| Exhaust | 1.3125 | |
| Valve Timing | ||
| Inlet Opens. Deg. BTC | 29 | |
| Inlet Closes, Deg. ABC | 71 | |
| Exhaust Opens, Deg. BBC | 67 | |
| Exhaust Closes, Deg. ATC | 33 | |
| Timing Point | Valve 0.004 In. Off Seat | |
| Engine Oil Pressure, Maximum P.S.I. | 33 | |
| Crankcase Oil Capacity, Qt. | 4 | |
