Pontiac FIREBIRD 1972 Service Manual page 612

6-100 1972 PONTIAC SERVICE MANUAL
SPECIFICATIONS
-
6 CYL. ENGINE
Type
..................................................................
In-Line 6
Valve Arrangement
..........................................
In Head
Bore and Stroke
......................................
3.87"
X
3.53"
Piston Displacement
......................................
250 cu. in.
....................................................
Taxable Horsepower 36
..................................................
Compression Ratio 8.5: 1
Horsepower
........................................
145
@
4200 rpm
Torque
......................................
230 lb. ft. @ 1600 rpm
Compression Pressure at Cranking Speed
Wide-Open Throttle
..................
140 psi @ 160 rpm
Firing Order
..................................................
1-5-3-6-2-4
............
Production Engine Number Pad at Right Front
Side by Distributor Shaft Hole
................
Cylinder Numbers-Front to Rear 1-2-3-4-5-6
CAMSHAFT
MateriaLCamshaft
..........
Hardened Alloy Cast Iron
..............................
Material-Cam Bearings High Lead
Steel Backed Babbitt
Journal Diameter
..........................
1.8682"
-
1.8692"
Bearing Length
..................................................
.807"
..............................
Bearing Clearance .0007"
-
.0027"
End Play
..............................................
.009"
-
.013"
CONNECTING RODS
Material-Connecting Rods
..........
Drop Forged Steel
Material-Rod Bearings
..........
Copper Lead Alloy or
Sintered Copper Nickel
Length, center to center
....................................
5.70"
Bearing Clearance on Crankpin-Limits
When New
.....................................
.0007"
-
.0027"
End Play of Connecting Rod on
Crankpin
............................................
.009"
-
.014"
CRANKSHAFT
Material-Crankshaft
....................
Cast Nodular Iron
Material-Crankshaft Main Bearings
......
Durex 100-A
Steel Backed
Journal Diameter
..........................
2.2983"
-
2.2993"
Bearing Length-Overall
1-2-3-4-5-6
......................................................
.752"
7
......................................................................
.76OV
Thrust Taken On
..................................................
#7
Crankpin Journal Diameter
..............
1.999"
-
2.000"
Pin Maximum Out of Round (New)
................
.002"
Pin Maximum Taper (New)
............................
.0003"
End Play-Limits When New
................
.002"
-
.006"
Main Bearing Clearance-Limits
When New
......................................
.0003"
-
.0029"
FLYWHEEL
Teeth on Ring
..................................................
153
Teeth on Starter Pinion
............................................
9
PISTONS AND CYLINDERS
Cylinder Bore Diameter
................
3.8745"
-
3.8775"
Cylinder Bore Out-of-Round
When New
........................................
.0005" (max.)
Cylinder Bore Taper When New
........
.0005" (max.)
Piston Material
......................
Cast Aluminum Alloy
............
Piston Clearance in Cylinder
.0005"
-
.0015"
Piston Ring Gap
Compression Rings
...............I
.............
.01O0
-
.020"
Oil Ring Segments
............................
.015"
-
.055"
Piston Ring to Groove Clearance
Compression Rings
Upper
..........................................
.0012"
-
.0027"
Lower
..........................................
.0012"
-
.0032"
Oil Ring Assembly
..........................
.000lV
-
.005"
PISTON PINS
Piston Pin Material
..........................
Chromium Steel
........................
Fit in Piston .00015"
-
.00025" loose
with piston and pin at 70" F.
Fit in Rod
....................................................
Press Fit
..........................
Diameter (Selective) .927OV
-
.9273"
................................................
Length 2.990"
-
3.010"
SPROCKETS
Camshaft-Material
....................
Bakelite and Fabric
Composition with Steel Hub
-Number of Teeth
...............................................
54
Crankshaft-Material
..........
Steel, Sintered Iron Hub
-Number of Teeth
................................................
27
VALVE TIMING (In Crankshaft Degrees)
............................
Camshaft (without A.I.R.) 3864497
Intake
Opens
......................................................
25" BTC
..................................................
Closes 237" ATC
.....................................................
Duration 262"
Lift (@ Zero Lash)
....................................
.388"
Exhaust
....................................................
Opens 236" BTC
....................................................
Closes 26" ATC
......................................................
Duration 262"
Lift
(@
Zero Lash)
....................................
.388"
Valve Overlap
......................................
.289" inches