Cadillac 1933 V8 Operator's Manual page 143

67B
ENGINE—Service Information
In most cases, the cylinder heads are plainly marked so
that they may be easily identified, but the safest method is to
determine the thickness of the head as measured from the top
flange to the surface which rests against the gasket. Both
means of identification are given in the table of gaskets
presented on page 67A.
When the part number of a cylinder head is definitely
established, the proper gasket to use in order to obtain the
desired ratio may be determined by referring to the table.
In any case where the " C " series head with the " C " series '
gasket, part number 889361, is installed on 370-A or B cars,
it will be necessary to install V-16 push rods, part number
84244, in place of the original V-12 rods to compensate for
the difference in thickness of the heads. This is in addition to
the changes in the timing required.
18. T w o T y p e s of P i s t o n s U s e d i n 345-C a n d 355-C
E n g i n e s
Beginning with engine unit N o . 30-990 on 345-C and 355-C
engines, the pistons are of a different design than those used
prior to this number. The changes in the pistons are in the
rings and the lands between the ring grooves as shown in H g .
1 on this page.
The ring change is in the second groove from the top. This
groove is now ft in. wide and contains two in. compression
rings which are effective in preventing blowby and the con-
sequent loss of power.
The two lands between the compression rings and the upper
oil ring are chamfered toward the top to aid in keeping down
the oil consumption. T h e top land at the top of the piston is
also grooved to prevent as much as possible the dissipation of
heat to the rings and the lower part of the piston.
Only these second type pistons are supplied for service in
the standard, .015 in. and .030 in. sizes for all " A , " " B " and
" C " series cars Likewise these pistons will be supplied with
all factory reground .015 in. and .030 in. oversize cylinder
blocks, not only for these series cars but for the earlier models
beginning with the Cadillac 341-A and LaSalle 340.
19. W o r n L i m i t s for C y l i n d e r B l o c k
When ordering first or second oversize cylinder blocks from
the factory, care should be exercised in determining the amount
of wear on the blocks returned for exchange as this wear on
the replaced blocks should determine the size of blocks to
order.
If the standard size cylinder blocks show less than .012 in.
wear or out-of-round they may be returned in exchange for
first oversize blocks. If the wear exceeds .012 in. but is less
than .027 in., second oversize blocks should be ordered for
installation on the car.
20. New T y p e C h a i n H o u s i n g O i l Seal o n 345-C a n d
355-C E n g i n e s
Beginning with engine unit 30-1256 on V-8 cars, a new type
oil seal is provided in the chain housing around the water
pump drive. This new seal consists of a felt and cork packing
in addition to the metal retainers which are retained in this
construction. The design of the oil seal is such that it cannot
be installed on engines prior to this engine unit number.
21. A d j u s t m e n t of V a l v e S p r i n g Pressure o n V-12 a n d
V-16 E n g i n e s
The relation between valve spring pressure and valve travel
on V-12 and V-16 engines is such that each .010 inch of travel
is equivalent to 2.73 pounds of pressure. In consequence, the
seating pressure of the valves may be reduced considerably
by the slight increase in travel occasioned by a valve refacing
and reseating operation. Reduced valve seating pressures
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5/32 in. oil ring
3/16 in oil ring
F i g . 1. V i e w s h o w i n g p i s t o n c o n s t r u c t i o n
a n d r i n g a r r a n g e m e n t , b e g i n n i n g w i t h
engine u n i t 30-990 o n 345-C a n d 355-C
engines.
would, moreover, affect engine performance to a noticeable
degree, especially in making cold-weather starting more
difficult, and in some cases might cause the valves to Burn.
T o control the valve seating pressure it should accordingly
be checked after valve refacing operations on V-12 or V-16
engines. Tool, Part N o . J-444 should be used for making this
test.
T h e correct seating pressure for the valves on V-12 and V-16
engines, with both valve springs properly installed, is from
48 to 63 pounds. If the pressure is less than 48 pounds, one
or more spacers should be installed under the valve spring
retainers. A spacer .040 inch thick is available for this
purpose, under Part N o . 889407. E a c h spacer will raise the
seating pressure 10.9 pounds.
E a c h valve should be tested separately and one or more
spacers installed as required. In case of an extremely low
seating pressure, the valve springs should be checked against
the specifications given on page 63 to make sure that they have
not lost tension and shortened in use.
22. M a k i n g L a t e r C h a n g e s i n E a r l y V a c u u m P u m p s
Beginning with engine number 2002446 on 345-C cars and
engine number 3001589 on 355-C cars, a vacuum pump of
slightly different design is used to aid in preventing loss of
engine oil. These changes are in the location of the vent hole
in the lower pump body, the spring above the diaphragm and
in the diaphragm.
The vent hole in the lower pump body is on the right side
in the first type pump and on the left side in the second type
pump as viewed from the top.
T h e second type spring above the diaphragm can be iden-
tified by the number of coils, the first type springs have twelve
coils whereas the second type springs have fifteen coils. T h e
new diaphragm is made of improved material. Only this
type diaphragm is carried by the Factory Parts Division.
These changes should be made in any 345 or 355 " B " or " C '
series cars before the engine numbers given whenever the
diaphragm is found cracked or broken or the pump is con-
tributing to excessive oil consumption.
Although these changes do not apply to the vacuum pump
on V-12 and V-16 engines, it is recommended that a new
diaphragm, (Part N o . 856331) and a lighter spring (Part N o .
856358) be installed in cases of diaphragm breakage but under
no circumstances should an attempt be made to change the
location of the vent hole in V-12 and V-16 vacuum pumps.
August 1933