VN 54 | APRIL – JUNE 2019 15
HONING
PERFECTION
Federal-Mogul Engine Expertise shares some insight on
honing – the finishing touch for the perfect cylinder bore.
Cylinder bore honing is a highly effective way to improve the bottom end of an engine. It is an
essential step after an engine re-bore, as a “tidying-up” procedure. Cylinder bore honing is also
effectively remedy’s an engine that is over-consuming oil or causing excessive smoke.
Federal-Mogul offers an overview of honing and how to accomplish it correctly, first time.
STEP-BY-STEP HONING
Step 1: Bore the Cylinders Step 4: Plateau Honing
The main bearing cap should always be
torqued into position. Using correctly
sharpened boring tools, it is important
to avoid removing too much material. If
too much has been removed, it cannot be
replaced. Rule of thumb is to leave at least
0.03mm each side for honing. To create smooth plateaus for the rings
to bed in and seal, peaks from the bore
surface need to be removed by honing
with 600 grit stones. Once completed,
the deeper valleys left after Step 3 can
still be seen. These are essential for oil
retention, to reduce ring and piston wear.
Meanwhile, the plateaus help to control
oil consumption through positive ring
sealing. For this step, one should hone
for at least 30 seconds in each bore – still
keeping the cross-hatch angle at 120°.
Step 2: Oil it Up
Honing needs done be done in several
stages to achieve the optimum finish.
Honing oil should be continuously applied
at all stages to cool the cutting surface,
while flushing away debris and maintain
the sharpness of honing stones. Use only
recommended honing oils – filtered
when possible to remove grit and debris.
Starting with 70 grit stones to remove
0.04mm, leaving 0.02 for finish honing –
at this stage, all boring tool marks would
have been removed to achieve a cross-
hatch finish.
Step 5: Cleaning Up
Bores need to be cleaned thoroughly after
honing. Hand-cleaning with hot soapy
water and a nylon bristle brush work best
as solvents or pressure washers are simply
not effective enough. A thoroughly clean
bore will come out stain-free after a lint-
free rag is wiped around the cylinder walls.
Step 6: Dry & Coat
Step 3: Working Your Way Down
Using 220 grit stones, the cylinder bore
needs to be honed down to the required
finished size. This involves removing at
least 0.02mm of extra bore material from
the previous stage. Be sure that the cross-
hatch angle of 120° is maintained and the
bore taper is controlled.
Dry the bores and coat them with oil.
After engine assembly, clean the bores
once more to remove any new dust
and grit. This creates a honed cylinder
which should help the engine to pass any
emissions test it takes.
FPS stocks everything you need to achieve the perfect honing, speak to your local FPS representative for full details.