1978 Corvette: Service Bulletin: Tamper Resistant Choke

Subject:   Tamper Resistant Choke
Model and Year:   1978 Corvette with Federal (L-48) A/C and Automatic Transmission
Source:  Chevrolet Dealer Service Information Bulletin
Bulletin No:   78-I-44
Section:    VIm
Date:   June, 1978

TO:  ALL CHEVROLET DEALERS

Some 1978 Corvettes as of March 1, 1978, are being equipped with a tamper resistant choke design to discourage readjustments of the choke cover-coil assembly.  Corvettes involved are those equipped with the Federal 350 engine and air conditioning and automatic transmission.  The carburetor with the tamper resistant choke design is P/N 17058206; this replaces carburetor P/N 17068204.

Instead of using a scribe mark for choke cover indexing, a special cut-out is machined with the choke cover at the three o’clock position, which matches a tab on one new cover retaining clip.  The three choke attaching screws have been replaced with pop-rivets.

NOTE:  The choke thermostatic cover should not be removed except during major carburetor overhaul or during replacement of cover and coil or choke housing.

Service Procedure

Removal of Choke Cover

1.  Carefully align a #21 drill (.159") on rivet head and drill only enough to remove rivet head.  Drill the two remaining rivet heads and then use a drift and a small hammer to drive the remainder of the rivets through the choke housing.

CAUTION:  Exercise care in drilling to prevent damage to choke cover or housing.

2.  Remove the three retainers, choke cover assembly and gasket from choke housing.

Installation of Choke Cover

NOTE:  Before installation of choke cover, check and, if necessary, adjust choke coil lever, choke rod (fast idle cam) and vacuum break to specifications.

1.  Start the three self-tapping screws in the choke housing, checking to make sure that screws start easily and are aligned properly, then remove screws.

NOTE:  The self-tapping screws are supplied with service kits.

2.  Place cam follower on highest step of fast idle cam.

3.  Install choke cover assembly and gasket on choke housing, make sure coil tang engages pick-up lever.

4.  Install retainer with tab at location A and align notch in cover with tab on retainers.  Install one self-tapping screw.

5.  Install the two remaining screws and tighten all three retainers securely.