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

Uslng a short sectlon of wlre cut and filed to match sprlng-installed helght to check seatto-retainer
distance. If thls dlstance Is too much, make up the difference up with a shim
and recheck uslng the wire "gage." When you've found the right combination, keep the
valve and shim together so you can install them in the same position as fitted.
If your gasket set includes the hard nylon
valve-stem seals rather than the lessdurable
soft oolvacrvlic seals. vou'll have
to use the instaliatlo; tool incl'uied in your
gasket set. Each seal is literally driven onto
Its stem while the valve Is supported under
its head.
than shimming it, even though a new
spring costs more than shims. If you do
shim some of your springs, make sure you
attach the shim to its spring with some
wire, string or whatever. If they get
mixed up, you'll have to retrace your
steps and recheck them.
ASSEMBLE YOUR CYLINDER HEADS
Now that all your cylinder-head parts
have been inspected and/or reconditioned,
you can get them all back together againsort
of like Humpty Durnpty. Except in
this case you won't need the King's
Horses or Men, just a valve-spring compressor
and a ruler, plus some valve-spring
shims-maybe. Yes, you may still have to
install shims even though you may have
gotten by without them up to this point.
ValveSpring Installed Height-One of the
valve-spring loads you checked was the
spring's installed height, or the height
the valve spring should be with the valve
closed and the spring and its valve, retainer
and shim/s installed. Shims are included
in the spring's installed height if
used to correct spring free height. Make
sure every spring is at its correct installed
height, otherwise its valve will not be
loaded correctly.
A valve stem projects out the top of
the guide when the valve is closed. The
distance from the cylinder-head spring
seat to the underside of the valve-spring
retainer installed on the valve, is also
determined by the valve seat.
As originally manufactured, this distance,
or pad-to-retainer dimension, coincides
with the valve-spring installed height.
However, because material is removed
from each valve face and seat during the
grinding process, this distance is increased
and consequently exceeds the installed
spring height. If your valve seats were in
good condition, only a small amount of
material should have been removed to
clean them up. Therefore, the spring's installed
height should not have been affected
to any great' degree. On the other
hand, if more material was removed, or
the heads have been rebuilt before, the
spring's installed height and load could be
changed considerably, so they should b,e
checked.
Because setting and checking installed
spring height is best done as part of the
cylinder-head assembly process, let's get
on with putting your heads together and
do the height checks at the same time.
Have your valves ready to be installed in
your heads in order and the springs with
their shims, if you used any to correct
valve-spring free height.
Installed spring height can be checked
by two methods. You can simply insert
the valve in the head, then assemble the
retainer and keepers on the valve stem
without the spring, shims or valve-stem
seal. The retainer is lifted up to hold the
valve in its closed position-it also keeps
the retainer and keepers from falling
down the stem-while the seat-to-retainer
dimension is measured. To get an accurate
reading, the retainer must be lifted up
firmly to ensure the valve is against its
seat and the retainer and keeper are in
place. A snap-gage and micrometers will
give you the most accurate reading when
making this measurement, however you
can do pretty well with a six-inch scale if
you have a sharp eye. A neat trick to use
is to cut, then file or grind a short section
of welding rod or heavy wire to the specified
installed height of the spring. You
can accurately check the rod length with
a micrometer. This will give you an accurate
gage which when placed between
the spring seat and the spring retainer will
show a gap the same thickness of the
shim required. The thickest shim that
best fits between the rod, retainer and
spring seat is the one to use.
If you've used the measuring method
to determine shim thickness, after you've
arrived at a shim-pad-to-retainer figure,
subtract the installed spring height from
it and you have the shim thickness required
to provide the correct installed
height. Therefore i
Shim thickness = spring-to-retainer
distance - installed spring height
Shims come in thicknesses of 0.015,
0.030 and 0.060 inch. They can be stacked
in varying combinations so you'll end up
with the right overall thickness.
The second way to check seat-to-retainer
distance varies only in that you install
the spring too. This means you'll have to
use the spring compressor to do so, but it
does ensure the reading will be accurate,
just more difficult to take. You won't be
able to use a snap-gage or anything between
the retainer and the spring seat.
One measuring device that works well
here is a pair of vernier calipers. You can
also use your less-accurate six-inch scale.
Measure the actual spring height in this
case by measuring from the spring pad to
the top of the spring. Regardless of the
method used, the way of arriving at shim
thickness 'is the same-subtract specified