Chevrolet CAMARO 1979 Service Manual page 524

647"18 Even Fire V-6
be replac€d. Oversize pins âre not practical due to the pin
being â press lit in th€ connecting rod. Piston pins must fit
lhe piston with an easy finger push ât 70'F (21'C)(.0004"
to .0007" clearance).
13. Exâmine all piston rings for scores, chips or cfâcks.
Check compression rings for tension bycomparingwith new
rings. Check gap of compresnon rings by placing rings in
bore at botlom of ring travel. Measure gap with feeler gage.
Gap should be between .010" and .020". If gaps âre
excessive (over.020") it indicates the rings have worn
consid€rably and should be replaced. Bore wear should be
checked before ings âre replâced, .005' bore weâr will
result in .015" increâse in ring gâp.
R E B O R I N G C Y L I N D E R A N D F I Î T I N G N E W
P I S T O N S
If on€ or mo!€ cylind€r bores are rough, scored, or
worn beyond limits, it will be necessary ro smooth or tru€
up such bores to fit new pistons.
If relatively few bores requir€ correction it will not be
necersar) ro rebofe all cylinders ro the rame oversrTe rn
order to mâintain engine balance, since all oversize service
pistonsâre held to the same weights as standârd size pistons.
Standard size service pistons are high limit (maximum
diameter); therefore, they can usually be used with a slight
amount of honing to correct Jighl \coring or excessive
clearânces in engines having relatively low mileage. All
service pistons are diâmond bored and selectively fitted with
p,slon pins: pi\rons are nor furni.hed withour pins.
No attempt should be made to cul down oversize
pistons to fit cylinder bores âs this will destroy the surface
treâtment ând affect the weight. The smallest possbile
oversize service pistons should be used and the cylinder
bores should be honed to size for prcper clearances.
Before the honing or reboring operation is started,
meâsure âll new pistons with micrometer contacting a
ooints exactly 90'to piston pin (Fig.6A7-36) then seiect the
smallest piston for the first fitting. The slight variâtion
usuâlly found between pistons in a set mây provide for
correction in case the first piston is fitted too f.ee.
If wear ât iop ofcylinder does not exc€ed .005" on the
diameter or exceed .003/ out-of-round, honing is
recommended for truing the bore. If wear or out-of-ûrnd
exceeds lhese limits, the bore should be trued up with a
boring bar of the fly cutter type, then finish honed.
When reboring cylinders, â11 crankshaft bearing caps
must be in piace ând tightened to proper torque to avoid
distortion of bores in finâl âssembly. Always be sure the
crankshâft is out oftheway of the boring cutter when boring
€ach cylinder. When taking the final cut with boring bâr,
leave.001" on ihe diameter for finish honing to give the
required clearance speciff ed.
When honing cylinders, use cleân sharp stones of
propet grade for the âmount of metâl to be removed, in
accordance with instructions of the hone manufacturer.
Dull or dirty stones cut unevenly and generate excessive
heat. When using coarse or medium grade stones use cârê
to leave sulnci€nt metal so thât all stone marks may be
removed with the fine stones used for finishing to provide
When finish honing, pass the hone through the entir€
lenglh ofcylinder ai the rate ofapproximately 60 cycles per
minute. This should produce ihe desired 45 degree cross
F g 6 A 7 J 7 P o s n r o n ' n 9 P i s l o n i n B o ' e
hâtch patiern on cylinder wâlls which will nÉure lrlaxrnum
ring life ând minimun oil consumption.
It is ofthe greatest importânce that refinished cyiinder
bores are trued up to have not over .0005" out-of-round or
tâper. Each bore must be final honed to remove all stone
or cutter marks and provide a smooth surface. During flnâi
honing, each piston must be fitt€d individually to th€ bore
in which it will be instâlled and should be rnarked to insure
correct instâllation.
After finâl honing ând before the piston is checked for
fit, eâch cylinder bore must be thoroughly wash€cl to remove
all trâces of âbrâsive and then d.ied thoroughly. Tbe dry
boreshould then bebrushed clean with a power-driven liber
brush. Ifall trac€s ofabrasive are not removed, rapid wear
of new pistons and rings will result. A satisfactory method
of fitting pistons is as follows:
L Remove âll rings from pistons which wiil be fitted.
It is not necessâry to separate rods from pistons, Ifan excess
amount of vamish or carbon appears as a ridge âr the top
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