Damaged Thread Repair

Reclaiming Cylinder Head Threads

Cylinder Head Tapped Holes:

Damaged or stripped threads in the cylinder head can be salvaged by fitting Helicoils as follows:

Holes
A - These three holes may be drilled 0.3906 in dia. x 0.937 + 0.040 in deep. Tapped with Helicoil Tap # 6 CPB or 6CS x 0.875 in (min) deep (3/8 UNC 1.5D insert).
B - These eight holes may be drilled 0.3906 in dia. x 0.812 + 0.040 in deep. Tapped with Helicoil Tap # 6 CBB 0.749 in (min) deep (3/8 UNC 1.5D insert).
C - These four holes may be drilled 0.3906 in dia x 0.937 + 0.040 in deep. Tapped with Helicoil Tap # 6 CPB or 6CS x 0.875 in (min) deep (3/8 UNC 1.5D insert).
D - These four holes may be drilled 0.261 in dia x 0.675 + 0.040 in deep. Tapped with Helicoil Tap # 4 CPB or 4CS x 0.625 in (min) deep (1/4 UNC 1.5D insert).
E - These six holes may be drilled 0.3906 in dia x 0.937 + 0.040 in deep. Tapped with Helicoil Tap # 6 CPB or 6CS x 0.875 in (min) deep (3/8 UNC 1.5D insert).

NOTE: Right-hand cylinder head illustrated.

F Exhaust manifold face
C Intake manifold face
H Front face
I Rear face
J Front of engine