GMC 4000 Series Service Manual page 275

Sec. 6A
Page 264
GASOLINE ENGINES
Except as otherwise indicated, the following specifications apply to both engine models.
EN GIN E T Y P E AND
NUM BER OF C Y L IN D E R S ............................................... In-Line, 6-Cyl.
CO M PRESSIO N RA TIO
250 En g in e........................................................................................ 8.5:1
292 En g in e.........................................................................................8.0:1
CYLIN D ER CO M PRESSIO N ( P S I)
At Cranking S p eed ............................................................................. 130
Max. Variation Between C y lin d e rs................................................... 20
S P A R K PLUG M A KE AND NUM BER
250 Engine................................................................................AC-R46N
292 En gine............................................................................. AC-CR44N
S p ark Plug Gap ( A l l) .................................................................... 0.035"
Plug Tightening Torque (F t .- L b s .).................................................... 25
IGN ITIO N D IS T R IB U T O R
Dwell Angle (D e g re es)................................................................... 31-34
Point Gap (N e w )............................................................................ 0.019"
Point Gap (U s e d )........................................................................... 0.016"
Contact Lever Spring Tension (O z .) ........................................... 19-23
T Y P E AND NUM BER
OF C Y L IN D E R S .............................................................................. 60°, V-6
CO M PRESSIO N RA TIO
305E, 305C En g ines....................................................................... 7.75:1
351C, 351M En g in es...................................................................... 7.50:1
C YLIN D E R CO M PRESSIO N ( P S I)
At Cranking Sp eed ............................................................................. 125
Max. Variation Between C y l............................................................... 30
S P A R K PLUGS
M ak e...................................................................................................... AC
Type and Gap
3 05 C ........................................................................ CR 44 NS, 0.040"
3 0 5 E ........................................................................ CR 45 NS, 0.035"
351C & 3 5 1 M ......................................................... C R 4 3 N,
Tightening Torque (F t .- L b s .)......................................................... 32
*At idling speed, with vacuum advance line disconnected and plugged.
**No-Load settings are approximately 200 rpm more than full-load settings.
G M C S E R V I C E M A N U A L
SPECIFICATIONS
IN -LIN E ENGINE TUNE-UP CHART
V -6 ENGINE TUNE-UP CHART
Specifications apply to all engines listed above unless otherwise indicated.
0.035"
FIR IN G O R D ER .........................................................................1-5-3-6-2-4
IG N ITIO N T IM IN G * .......................................... Refer to Chart (Fig . 17)
V A LV E L A S H ........................................................................................ Zero
N O TE: Valve lifters are hydraulic type. Refer to "C ylin d er
Head Bolt Torque and Valve Lash A d justm ent"
in this section for instructions.
EN GIN E ID LE SP EED (R P M )..........................Refer to Chart (Fig . 17)
FU EL PUMP P R ESSU R E ( P S I ) ...................................................
C Y LIN D E R HEAD BO LT
TORQUE ( F T .- L B S .) ................................................................................ 95
*A t engine idling speed, with vacuum advance line disconnected
and plugged.
IGN ITIO N D IS T R IB U T O R
Dwell Angle (D e g re es)...................................................................31-34
Point Gap (N e w )............................................................................ 0.019"
Point Gap (U se d )........................................................................... 0.016"
Contact Lever Spring Tension (O z .)........................................... 19-23
FIR IN G O RD ER......................................................................... 1-6-5-4-3-2
IGN ITIO N T IM IN G * .......................................... Refer to Chart (Fig. 17)
VA LV E LASH
In ta k e .............................................................................................. 0.012"
Exh au st............................................................................................ 0.018"
EN GIN E GOVERNOR S E T T IN G (Fu ll Load R P M )**
3 05 E& 305C ...................................................................................... 3400
351C .......................................................................................... 3600
351M ................................................................................................... 3400
EN GIN E IDLIN G SP E ED (R P M )..................... Refer to Chart (Fig . 17)
FU EL PUMP PR ES S U R E ( P S I ) ........................................................... 5-6
C YLIN D E R HEAD BO LT TORQUE ( F T .- L B S .)
W i- V /i
............................ 6 0-65