Pontiac tempest 1968 Service Manual page 331

6B-24
1968 P O N T I A C SERVICE MANUAL
Fig. 6B-57 Choke Coil Rod Adjustment
CHOKE ROD ADJUSTMENT (Fig. 6B-54)
Place Idle screw on second step of fast idle cam
against shoulder of high step. While holding screw
in this position, gauge between upper edge of choke
valve and air horn wall. Adjust to specified dimen­
sion by bending tang on choke lever and collar
assembly.
After the carburetor is assembled the following
adjustments must be checked.
VACUUM BREAK ADJUSTMENT (Fig. 6B-55)
With vacuum break diaphragm seated and choke
valve closed so the vacuum break rod is at the end
of the slot in the choke shaft lever, gauge between
the upper edge of the choke valve and inside wall of
the air horn casting. To adjust, bend the vacuum
break rod.
UNLOADER ADJUSTMENT (Fig. 6B-56)
With the throttle valves held wide open the choke
valve should be open enough to admit the specified
gauge between the upper edge of the choke valve and
inner air horn wall. Bend tang on throttle lever to
adjust.
CHOKE COIL ROD ADJUSTMENT (Fig. 6B-57)
To adjust, disconnect the upper end of the choke
coil rod from the choke lever. With choke valve
completely closed, pull upward on the choke coil rod
to the limit of its travel. The end of the rod should
fit the gauge notch on the choke lever.
To adjust, bend rod as shown.
ROCHESTER 4 M V QUADRAJET CARBURETOR
Carburetor Engine and
Model Transmission Car
Number
Usage Model
7028260 250 A . T .
A & F
7028261 250 M.T. A & F
7028262
400 A . T . B
7028263 400 & 428 M.T. A & B
7028264
400 & 400 H.O. A . T . \ F
7028265 400 M.T. F
7028266 350 A . T .
A & F
7028267
400 H.O. & 428 H.O. M.T. A & B
7028268 400 & 400 H.O. A . T .
A
428 & 428 H.O. A . T . B
7028269 350 M.T.
A & F
7028271 400 H.O. M.T. F
7028274 400 Ram-Air A . T . A
7028275 400 Ram-Air M.T. A
7028276 400 Ram-Air A . T .
F
7028277 400 Ram-Air M.T. F
mixture adjustment and the unloader adjustment, all
adjustments are included in the OVERHAUL AND
ADJUSTMENTS procedure.
Whenever the idle speed screw is turned, the
throttle should be opened slightly, then closed to seat
screw properly on cam (with solenoid disconnected).
The idle mixture should be adjusted to give a
smooth idle at the specified idle speed. Missing is a
sign of too lean an idle mixture while rolling or lop­
ing indicates too rich a mixture. Turning the idle
mixture screw in leans out the mixture; five turns
out from the lightly seated position may be used as a
preliminary setting of the mixture screws on six-
cylinder engine, and six turns out on V-8 engines.
The mixture is to be leaned out from this initial
setting to achieve the best lean idle.
Car Model Code:
A - Tempest B - Pontiac F - Firebird
Carburetor identification a n d change code is
stamped on the throttle lever side of the float bowl.
A D J U S T M E N T S O N C A R
All Rochester 4MV adjustments can be performed
on the car. With the exception of the idle speed and
PERIODIC SERVICE
R O C H E S T E R 4MV C A R B U R E T O R
There are no periodic services required on the
Rochester 4MV carburetor; however, choke linkage,
choke valve and levers and pump linkage should be
kept free of dirt and gum so that they will operate
freely. DO NOT OIL LINKAGE.