1955 - 1956 Corvette: Service Bulletin: Inlet Manifold Oil Guards

This bulletin covers all 1955 Corvettes except the small number of 1955 Corvettes built with V-6 engines. The number of 1955 Corvettes built with V-6 engines is believe to be less than 10 units. With the date of 6/15/56 given in this bulletin, the oil guard redesign took place in 1956 Corvette serial number range 2,080 to serial number 3,467.

Subject:    Inlet Manifold Heat Requirement
Model and Year:  265 V-8 Truck and Passenger Engines - 1955-1956
Source: Chevrolet Technical Service Bulletin
Bulletin Number: DR #253, Section VI
Date:   June 29, 1956

TO:  ALL CHEVROLET DEALERS

In heavy-duty truck operations where ring plugging, inlet manifold crossover filling and malfunctioning of tappets is experienced due to localized hot spots, as covered in TSB #391 - DR #244, dated March 30, 1956, an Inlet Manifold Oil Guard is in production and available in service to further minimize this condition.

The oil guard entered production on engines, both truck and passenger at the Flint Engine Plant on June 15, 1956.

PARTS DATA

SERVICE INSTALLATION PROCEDURE

Remove old guard by cutting off the heads of four drive studs which hold the guard in place.  This may be accomplished by using a cold chisel.  The remaining part of the stud is to be left in to seal up the hold.

NOTE:  A careful inspection should be made to determine that the remaining shank of the drive rivet is tight in the manifold.  Should one of the drive rivets fall out, a leak would occur which would permit exhaust gasses to enter the tappet deck and exit through the oil separator at a rate which might cause oil pull-over.

Place the new #3735442 guard in place on the underside of the manifold.  Since the new guard will locate itself when laid in place, it may be used as a template for locating the four holes to be drilled for attachment.  Outer four (4) holes are for service attachment - one located at each corner.

On early engines having long ventilator (oil separator) it will be necessary to cut a relief in the guard.  When short ventilators are available in Parts Stock the ventilator may be changed.

Prick Punch the location of the outer holes and using a #29 or 9/64" drill, drill the holes in the passages.

NOTE:  Care should be taken to drill the holes as straight as possible with a minimum amount of wallowing.

The guard is held in place by four #456819 round head grooved drive studs.  These should be coated using a sealing substance, such as, Gas-Oila, Perma-Tex #1 or some similar substance.

V-8 TRUCK ENGINE CARBURETOR TO MANIFOLD GASKET

As a means of further heat reduction at the carburetor and elimination of hard starting a new carburetor to manifold gasket which restricts heat to the carburetor base is now in production and available in service for use on trucks.

E.L. Harrig
Manager, Service and Mechanical Department