How To Rebuild Your Ford V-8 351C-351M-400-429-460.pdf - Index of

or 68 lbs. in this case. If a spring does not
exceed or at least meet the minimum, it
should be replaced. If your engine will be
operated at its upper RPM limit, or is one
of the high-performance models, you
should make sure valve-spring load at
least meets the minimum standard limit.
Load at Open Height-Another commonly
listed specification is a spring's compressed
load when its valve is fully open. A typical
specification is 240-266 lbs. at 1.330
inches. Just as with the installed-height
load, a spring must fall within the 10%
minimum-load limit or be replaced. In
this case, the minimum is 216 lbs. Again,
consider how your engine will be operated
when checking the springs.
Solid Height-Solid height describes the
height of a coil spring when it is totally
compressed to the point where each coil
touches the adjacent coil. The spring is
said to coil bind, or go solid. Coil springs
should never be compresed to this height
in normal service. If a valve spring were to
reach its solid height before its valve is
fully opened, the load on the valve train
would theoretically approach infinity.
But before this could happen, the weakest
component in the valve train will failsomething
bends or breaks-usually a
pushrod.
Squareness-Valve-spring squareness is
how straight a spring stands on a flat surface,
or how much it tilts. It is desirable
for a spring to be square so it loads the
spring retainer evenly around its full circumference.
Uneven retainer loading increases
stem and guide wear-something
you should minimize. Limit out-of-squareness
to 1/16 inch measured from the top
of the spring to a vertical surface with
the spring sitting on a horizontal surface.
CHECK YOUR VALVE SPRINGS
Of the spring characteristics just
covered, the ones which should be checked
are squareness, and the installed and open
spring loads, plus making sure the spring
doesn't reach its solid position in the fullopen
position. A flat surface, square and
something to measure with are all that's
required to check for squareness. When
you're all set up, rotate the spring you're
checking against the square to determine
its maximum tilt, then measure it. If the
gap at the top of the spring exceeds 1 /I 6
inch, replace it.
As for the last two checks, a valvespring
tester is required. Two types of
testers are normally used, but both do the
same thing. They permit manual compression
of a spring to the opened and installed
heights so the spring's loads at
these heights can be read. The question is,
Two quick and easy ways of determining whether your valve springs need shimming and/
or replacing. Squareness is being checked with a carpenter's framing square. Spring
should lean no more than 1 /16 inch at the top. If you find free heights of your springs varying
as much as these two, you'll know more comprehensive checking is needed.
Checking spring load at installed height. Rechecking weak spring to see if 0.030-
Shimming brings spring load within inch shim will bring its installed-height load
specification, then spring-is checked at withln specification. Remember, indiscrimiopen
height to ensure it doesn't go solid. nate use of shims can cause big trouble
You should be able to see daylight between when trying to correct spring load, so
each coil at open height.
check for clearance between each coil at
open height.
"How do I check for spring load if I don't
have a spring tester" The answer is
simple, you don't!
Fortunately, a simple method can be
used to determine if the spring is usable:
compare its free height to that originally
specified. A spring which has been fatigued
or overheated, usually from excessive
engine temperatures, will sag or collapse
some amount. This is reflected in a
spring's free height. A sagged spring's load
is reduced in the installed and open positions,
or heights.
Also, when a spring is removed from