Procedure - od165180020

Welding Operations, I
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engine blocks.

When using the shielded metal-arc method of

repair, a welding rod with a high nickel content of at least 50

to 60 percent must be used. Cracks in a cast iron engine block

must be properly prepared prior to welding, otherwise (after

cooling), the weld deposit shrinks, which pulls the crack

together and results in the formation of internal stress.

This

stress finally relieves itself by cracking due to continued

vibration during engine operation. Subsequent paragraphs provide

the steps that should be followed to eliminate this stress and

effectively repair the crack.

1 Drill a 1/8 inch diameter hole 1/4 inch beyond each end of

the crack as shown in figure 3, view A, on the previous page.

2 Clean and groove the crack and remove the "as cast" surface

or skin by grinding or machining.

3 Preheat the casting by baking or locally heating the

casting at 1000 Fahrenheit for a few minutes to remove all

moisture.

(It is imperative that all moisture be removed,

otherwise the weld will not adhere to the base metal.)

4 Drill and tap a hole to receive a 1/4 inch bolt in the

center of the crack as shown in figure 3, view B.

Screw and

tighten a bolt slightly deeper than the thickness of the base

metal. Stake the sides of the bolt with a center punch so that

it will not back out, and cut off the bolt as shown in figure 3,

view C.

5 Weld the crack using the backstep method shown in figure 3,

view D, and peen each bead with a round nose tool.

6 The minimum preheat and interpass temperature should not be

below 400 to 500 F when using a nickel rod, and the weld should

not be allowed to cool when applying more than one pass. If all

the impregnated oil or gas is not eliminated during preheating,

the first pass will usually be too porous and must be removed and

the weld repeated until a sound first pass is obtained.

7 Allow the completed weld to cool

slowly

placing

asbestos blanket over the welded area.