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

You can usually feel valve movement in a guide regardless of whether
judging guide wear. A better check is to install a valve in the guide so its tip is even with the top of the guide. Measure how much it wiggles-the
difference between A and B. Divide this figure by 3 to get the approximate stem-to-guide clearance. Measure the wiggle sideways
too. Block the head up so the guide is parallel to the surface you are measuring from.
enough to cause head and manifold
misalignment problems. A nearby chart
provides machining requirements related
to cylinder-head milling.
Rocker-Arm-Stud Replacement-Three defects
require the replacement of a rockerarm
stud: damaged threads, a broken stud
and one that isnotched. Notching occurs
when a rocker arm used with the balltype
fulcrum rocks over on its side, resulting
in the edge of the clearance hole
in the rocker arm contacting the stud.
This wears a notch in the side of the stud,
and could cause the stud to break. Replacing
a stud is relatively simple. Unscrew
the old one and thread in the new one.
You'll need DOOZ-6A527-A if yours is
the positive-stop type and C9ZZ-6A527-A
for the adjustable type.
VALVE GUIDES AND VALVE STEMS
Valve-guide inspection and machining
marks the beginning of hard-core cylinder-head
machine-shop-type work which
carries over into valve and valve-seat reconditioning.
This work requires special
equipment and special skills. If done incorrectly,
it will ruin what would otherwide
be a successful rebuild. If a valve
guide is badly worn, it won't guide the
valve so it can close squarely on its seat.
Consequently, a valve can't seat properly
as it will wiggle and bounce on the seat
before closing. It may not even fully close
at high RPM. This eventually beats out a
valve seat and accelerates guide wear.
Secondly, a worn guide lets too much oil
pass between the valve stem and guide,
resulting in excessive oil consumption.
With these points in mind, I'll cover
the basics involved in reconditioning your
seats, guides and valves.
Measuring Valve-Guide Wear-There are
four ways to measure valve-guide wear:
With a dial indicator at the top of a valve
located in the guide, by wiggling the valve
in the guide and measuring its movement,
wih a taper pilot and a micrometer or
with a small-hole gage and micrometer.
To check guide wear or clearance with
a dial indicator, install a valve in the guide.
Mount the dial indicator 90" to the valve
stem in the direction you want to measure
wear. Maximum wear usually occurs.
in the plane of the valve stem and the
rocker-arm pivot. It can be in the opposite
direction-in the plane running lengthwise
with the head if rail rocker arms are
used. With the valve about 118 inch off
its seat and the indicator tip-it should
be a flat one-contacting the valve stem
close to the top of the guide, hold the
stem away from the indicator and zero its
dial. Push the tip-end of the valve stem
toward the indicator and read the clearance
directly.
Wiggling a valve in its guide to determine
guide wear requires a minimum
amount of equipment. It's not the most
accurate method, but it's good enough to
determine whether your guides need
attention. It's done by measuring how
much a valve wiggles, or moves at its
head when pulled out of its guide. The
amount of wiggle divided by 3 is approximately
the stem-to-guide clearance of a
new valve in the direction of movement.
Measure valve wiggle with a dial indicator
or the depth-gage end of a vernier
caliper to be accurate. Using a taper
pilot is the least dependable way of determining
guide wear. A taper pilot is a
tapered pin inserted into the end of a
guide until it is snug. The diameter where
the pilot stops is miked to determine
guide diameter at its top or bottom. The
measured diameter less the specified
guide diameter is taken as the amount of
guide wear-but it's not correct. The pilot
measures the minimum distance across
the guide rather than the maximum distance.
It's the maximum distance you
should be looking for, so don't use this
method.
The most accurate method of determining
guide wear is to use a small-holegage.
You'll want the C-gage. Unfortunately,
a small-hole-gage set costs
about $30, and that's the only way
you can buy them, in a set. However,
if you have access to one, or have decided
to make the investment, here's how
to use it.
Insert the ball-end of the gage in the
guide and expand it until it fits the guide
with a light drag. Check the guide bore
at several places up and down and around
the bore to locate maximum wear. After
setting the gage, withdraw it and mike
the ball end. This will give you a direct
measurement of the guide-bore cross
section at the specific point you're checking.
Subtract the valve-stem diameter
from this figure and you'll have maximum
stem-to-guide clearance. Measure
around the guide at its top and bottom to
find maximum wear. If the difference
between maximum and minimum wear,
or out-ofround exceeds 0.002 inch, your
guides should be reconditioned.
How Much Guide Clearance-Maximum
stem-to-guide clearance is 0.005 inch.
New stem-to-guide clearance range is