TM 5-3825-226-24
BASIC BLOCK
CYLINDER BLOCK HONING
The following preliminary check is essential to
determine if honing is necessary, and if so, the size to
hone.
Measure all cylinder bores during disassembly
using the 1P3537 Bore Gauging Group. This group
includes a 1P3535 Dial Bore Gauge Group and a
1P3536 Size Setting Fixture Group. The bore gauging
group provides more accurate measurements than other
methods, such as inside micrometers. When setting the
gauge, always be sure the gauge pin has sufficient
travel to measure the points of maximum wear in the
bore. In a cylinder bore, maximum wear is usually
across the diameter perpendicular to the crankshaft
centerline, either at the top or bottom of ring travel.
Normal wear usually will not exceed .020 in. (0.51 mm);
however, if bore wear is greater than .020 in. (0.51
mm), hone the block .040 in. (1.02 mm) oversize. The
fact that the block can be honed both .020 in. (0.51
mm) and .040 in. (1.02 mm) oversize will allow a block
to be reconditioned twice under normal wear conditions.
The standard bore size is 4.5000 to 4.5015 in. (114.300
to 114.338 mm).
1P3537 BORE GAUGING GROUP
When reconditioning an engine, the bore size is
the determining factor as to the necessity of honing the
bores. If bores are worn .006 in. (0.15 mm) more than
the standard size, the block should be honed. However,
additional service may be obtained without honing if
wear does not exceed the maximum wear limit of .0085
in. (0.216 mm)
Before honing, inspect the bottom of each
cylinder bore adjacent to the main bearing saddle or
web. Some of the saddles may overlap the edge of
cylinder bores enough to interfere with honing. Where
overlap exists, machine a relief in the saddle to provide
clearance for the honing tool. The radius of the relief
must be concentric with the cylinder bore and .030 ±
.005 in. (0.76 ± 0.13 mm) larger than the bore radius.
The relief extends .62 in. (15.7 mm) beyond the bottom
of the bore, as shown. This provides adequate
clearance for honing.
RELIEF IN SADDLES and CHAMFER AFTER
HONING
When honing, check bore size at several
locations in the length of the bore and around the
circumference.
Specifically
measure
at
points
perpendicular to the crankshaft centerline at locations
.25 in. (6.4 mm) from each end and at center of bore.
These three specific locations are primary gauge points
during and after honing.
PRIMARY GAUGING POINTS
3-365
