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 (r) Use clean fuel oil and wash the Prussian blue
the crankshaft. Examine the bearing; any high spots will be
from the crankshaft bearing surface. Place a wooden plug in
clearly indicated by blue marks left from the prussian blue. At
the crankshaft oil hole cut flush with the crankshaft bearing
least 80 percent of the bearing surface should contact the
surface. Apply a thin coat of medium grinding compound to
crankshaft bearing surface, if it does not-the bearing must be
the crankshaft bearing surface. Lap the main bearing to the
scraped to fit.
crankshaft. To remove any scratched or small digs left from
(i) Use a machinist's scraper and scrape the high
scraping, proceed as follows:
spots indicated by the Prussian blue: scrape very little at a
1. Replace shims, and bearing cap. Tighten the
time. Replace the bearing as described in (1c), (d), (e), and
bearing cap stud bolts.
(f) above.
2. Rotate the crankshaft ten complete turns
(j) Remove bearing as described in (g) and (h)
forward and ten complete turns in reverse.
above. Continue the scraping until checks show that at least
3. Remove bearing cap stud nuts, bearing cap
80 percent of the bearing area contacts the crankshaft bearing
and shims.
Tag, the shims for proper reinstallation
surface. When the bearing has a good face-to-face contact
identification.
with the crankshaft bearing surface, the blue marks will show
4. Examine the bearing surface. If the small
on the bottom of the bearing and up the sides, covering about
scratches have not been removed repeat the lapping process.
80 percent of he bearing surface.
until the bearing surface is smooth.
5. After completing the main bearing lapping
NOTE
process, wash the bearing cap and bearing in clean fuel oil to
After scraping and adjusting the bearing,
remove he grinding compound, wipe dry with a clean, lint free
clean bearing before permanently fitting it
cloth.
to crankshaft. (k) Roll the properly fitted
bearing into the bearing saddle bore and
6. Wash the crankshaft bearing surface with clean
remove the jack from under the crank web.
fuel oil and wipe dry. Rotate the crankshaft during the
cleaning process.
(l) Replace shims on both sides of the main
7. Remove the lower bearing shell as described in
bearing from which they were removed. Check to see that the
b. (4) and (5) above.
crankshaft is sufficiently coated with Prussian blue. If not
8. Wash the lower bearing in clean fuel oil and
coat the crankshaft again.
wipe dry to remove grinding compound.
(m) Position the main bearing cap on the
9. Recheck the camshaft bearing surface for signs
crankshaft and tighten main bearing stud nuts. Roll crankshaft
of grinding compound. Wash in clean fuel oil and wipe dry.
over two turns.
10. Remove the wooden plug from the crankshaft
(n) Remove stud nuts and lift the bearing cap from
lube oil hole.
crankshaft. Examine the bearing shell. Any high spots will be
clearly indicated by the blue marks left from the Prussian
CAUTION
blue. High spots will have to be scraped.
Be sure to remove the wooden plug from
the crankshaft lubricating oil hole, or
NOTE
damage will result.
High spots are the blue marks left on the
sides of the bearing shell. These high
11.
Replace the lower main bearing in saddle
spots indicate poor bearing fit.
bore.
12. Remove the small jack from under the crank
(o) Use a machinist's scraper and scrape the high
web.
spots indicated by the Prussian blue. Scrape very little at a
13. Replace main bearing shims.
time.
(p) Replace bearing cap as described in (m)
NOTE
above.
After the main bearing has been scraped
(q) Continue to scrape and fit the bearing to the
and fitted to the crankshaft the bearing
crankshaft bearing surface, until checks show that at least 80
must be checked for proper clearance.
percent of the bearing area contacts the crankshaft bearing
area contacts the crankshaft bearing surface. When the
14. Take four pieces of .015-inch soft lead wire
bearing has a good face-to-face contact with the crankshaft
and place on the crankshaft main bearing surface. The lead
bearing surface, the blue marks, left from the Prussian blue,
wires can be held in place by grease.
will show on the top of the bearing and down the sides,
15. Replace main bearing cap and bearing shell.
covering about 80 percent of the bearing surface.
Tighten main bearing studs nuts evenly. Check to see that the
main bearing cap is drawn down evenly on the shims.
NOTE
16. Remove the main bearing cap, do not disturb
After scraping and adjusting the bearing
shims.
cap, clean bearing before fitting it to
crankshaft.
3-63
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