[Chrysler300] 300 C Carburator Metering Rods etc.

["John L. Chesnutt" <chesnutt@xxxx>]

Subject: Chrysler Confidential Technical Bulletin #364 - Fuel - Carburetor
Performance - 300 C


Several of you have asked about the above Bulletin #364, dated July 18,
1957. It modifies the service Bulletin No. 1002-Ch, dated March 1, 1957
which covers the data and specifications on the 1957 Chrysler 300C.

I do not think that changing to leaner metering rods will cure the problem
of
stumbling in turns. The stumbing on turns at low engine speeds is due to
the gasoline in the float bowl sloshing around and flooding out the carbs.
Technical Bulletin # 364, Step #6, changes the float setting by lowering the
float. The new settings are almost double the prior distance from the air
horn gasket to the float. The new float level settings are: ----- 1/4 inch
for the primary float and 5/16 inch for the secondary float with the air
horn gasket in place. The settings in Service Bulletin No. 1002-CH for the
300C, page 15, show float setting on primary 1/8 inch and secondary 3/16
inch.


GROUP - FUEL
SUBJECT - CARBURETOR PERFORMANCE
MODELS - ALL CHRYSLER C 300-C.

We have received reports of poor idle quality, stumble or hesitation on
acceleration, stalling on stops or sudden turns on some Chrysler 300C.
Considerable improvement of warm engine performance can be obtained by
following the
service correction outlined below:

1. Remove both carburetors from the engine and disassemble each into three
major sections: air horn, main body, and throttle body. Remove the floats
and fuel inlet valves from the air horn.

2. Drill four .0935" ( #42 drill ) holes through the vent passage boss in
the air horn as shown in Figure 1. Access to the vent passage boss behind
the choke housing on the rear carburetor may be obtained by cutting away
the
excess choke housing to air horn gasket.

3. Remove the main nozzle plug rivets on the primary side on the
carburetor.
Remove the idle tubes---primary side of carburetor. Enlarge the idle tube
wells to .209" by drilling with a #4 drill ( .209" ) as shown in Figure 2.
Use extreme care so that the idle tubs seat ( just below the threads in the
carburetor main body ) is not damaged, see Figure 3.

4. File the projecting pilot bosses on the primary side of the underside of
the main body to 1/32" as shown in Figure 3.

5. Clean carburetors thoroughly and blow out all passages with clean dry
compressed air. Install the nozzle passage plug rivets.

6. Assemble the air horns and adjust the float setting; 1/4 inch for the
primary float and 5/16 inch for the secondary float with the air horn
gasket
in place.

7. Install ( Carter #120-193) Chrysler Part #1631356 ( .057" ) secondary
jets in the front carburetor only. Use the original secondary jets in the
rear carburetor. Complete the assembly of the carburetors. Install ( Carter
#75-1160 ) Chrysler Part #1631394 metering rods in both front and rear
carburetors. Adjust the carburetors completely as described in the Chrysler
Service Manual and Chrysler Service Bulletin #1002-CH, dated March 1, 1957.
Make the preliminary idle setting by closing off completely the idle
by-pass
air screws of both carburetors. Set the idle mixture screws 1-1/2 turns
out.
The idle speed screw of the rear carburetor should be left backed out so
that the throttle valves seat. Back off the front carburetor idle speed
screw until the throttle valves seat in their bores, and then turn the idle
speed screw w in two complete turns.

8. Install the carburetors using a new 1/8 inch thick flange gasket. Start
and operate the engine to operating temperature. Adjust the front
carburetor
idle speed screw to obtain 650-700 engine r.p.m. Adjust the rear carburetor
idle mixture screws for best idle performance. Adjust front carburetor idle
speed screw for best performance. Reset the front carburetor idle speed to
obtain 650-700r.p.m.. Road test the vehicle to be sure performance is
satisfactory.

M. J. Kollins ( Chrysler Corporation ) Dated July 18, 1957


You can tell if your carbs have been modified as you can see the holes that
were drilled in the air horns. I have the supporting Figures 1, 2 and
showing the airhorn, main body and side view of the main body.

Hope the above will be useful to 300C & D owners.

John & Arlys Chesnutt, Portland, OR. 300C