Chevrolet DB90 Series, Service Manual

Page: 126 / 242

r
S ec. 6Y -120
Ignition sy ste m inform ation applicable to v e ­
h ic le s cov ered by this supplem ent rem ain s the
sa m e as covered under “ IGNITION SYSTEM" in
ENGINE ELECTRICAL (SEC. 6Y) in S e rv ic e Man­
u a ls ST 135-70 and S T 332-71, excep t a s follow s:
GENERAL
The ignition sy ste m c o n sists of the so u rce of
pow er (battery or generator) ignition sw itch, ig n i­
tion c o il, d istrib u tor, condenser, spark p lugs, and
high and low tension w ir e s.
A 1.52 OHM r e sista n c e w ire is in sta lle d in the
engine w iring h a rn ess on a ll v e h ic le s • equipped
w ith the V6 or V8 gasolin e engine (except S e r ie s
R M -70). T his w ire is in sta lled betw een the ig n i­
tion term in al on the ignition sw itch and the (+)
term in al on the ignition c o il.
On S e r ie s R M -7500, a 1.52 OHM ignition r e ­
sista n c e unit, mounted on the rear e le c tr ic a l equip­
ment control panel, is connected between the ign i­
tion coil (+) term inal and the engine control sw itch.
The r e sista n c e w ire or unit is used to in cre a se
ignition co il efficien cy and lengthen distributor
point life . If re sista n c e w ire b ecom es damaged,
rep lace with w ire of sam e gauge s iz e and length.
IMPORTANT: DO NOT u se copper w ire in
p la ce of the r e sista n c e w ire. When replacing a r e ­
sista n c e w ire or r e sista n c e unit, u se recom m ended
p a rts.
IGNITION TIMING
Inform ation applicable to ignition tim ing r e ­
m ains the sam e as coveredunder "IgnitionT im ing”
in "IGNITION SYSTEM" in ENGINE ELECTRICAL
(SEC. 6Y) in S ervice Manuals ST 135-70 and
ST332-71 except as follows:
On the V6 401M engine, se t tim ing to 7^u b e­
fo re u p p er-d ead -cen ter (BUDC) with engine running
a tQ525 rpm. On the V6 478M engine, se t tim ing to
1 / BUDC with engine running at 525 rpm; and on
the V8 637 engine, se t tim ing to 5 ° BUDC with
engine running at 475 rpm.
NOTE: If tim ing mark does not align with
pointer, loosen distributor mounting clam p cap
sc r e w and rotate distributor body a s required to
synchronize tim ing light fla sh es with tim ing mark
on engine crankshaft pulley. Tighten distributor
mounting clam p cap scre w after adjustm ent is
made.
IGNITION SYSTEM SPECIFICATIONS
ENGINE
DISTRIBUTOR
401M & 478M 478SN 637
Make ........................................................................................
Delco-Remy Delco-Remy Delco-Remy
Model No....................................................................................
1110478
1110451 1111985
Rotation (Viewed at Rotor) .......................................................
CW CW CW
Point Opening (In.) .................................................................... 0.016
Cam Angle (Degrees) (1) ........................................................... 31-34
31-34'” 28-32
Centrifugal Advance (2)
Start (Degrees) ......................................................................
0-2 0-3 1-3
R.P.M .................................................................................
510 450 550
Intermediate (Degrees) .........................................................
4-6 2.3-5.4
R.P.M ................................................................................. 750
530
Intermediate (Degrees) ......................................................... 6.5-8.5 3.6-5.6
5-7
R.P.M ...............................................................................
1100 570
800
Maximum (Degrees) ............................................................... 10-12
10-12 13-15
R.P.M ................................................................................. 1750
1800 1600
Firing Order .............................................................................. 1-6-5-4-3-2 1-6-5-4-3-2
i 8 i 3 6 5 / 2
Ignition Timing Point
Degrees .................................................................................
7 1 .2 ° BUDC 7 1/2° BUDC 5° BUDC
R.P.M. (Engine) ...................................................................... 525
500 475
(1) Set with vacuum advance line disconnected and plugged.
(2) Satisfactory Range. When adjusting set to 30 degrees. (Gives 0.016 point opening).
(3) Reconnect hose to opposite side of vacuum unit & adjust cam angle w-vac. full retard.
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