Pontiac tempest 1968 Service Manual page 294

V-8 E N G I N E
6-77
Pistons
Material Tin-PIated Aluminum Alloy
Type
o
Cam and Contour Ground - Slipper Skirt
Measurement Taken At . . . . .
0 0
. . . . Top of Skirt
Clearance in Cylinder
350 and 400 . .0025" - .0031"
428 .0030" - .0036"
Piston Rings
Compression Rings . . Two Cast Iron, Reverse Twist, Taper Face
Material Upper Lower
350 o . . . Channel Moly Filled Tin-PIated
400 G T O , Firebird 400 and 400 R.A Channel Moly Filled Channel Moly Filled
400 Pontiac . . .
0
. . Channel Moly Filled Tin-PIated
428 Channel Moly Filled Tin Plated
428 H . O . Channel Moly Filled Channel Moly Filled
O i l Ring Three-Piece
Material
Rails (2) Chrome-Plated Steel
Expander Stainless Steel
Ring Gap
Compression (±.010) .020"
O i l (± 020) , 035"
Side Clearance (Ring to Groove) .0015"-.005"
Piston Pin
Material Extruded SAE 1016 Steel
Diameter . . . . 9802"
Wall Thickness .38"
Length . . 3.25"
Fit in Piston 0005"-.0007"
Fit in Rod Press
Connecting Rod
Material Arma Steel
Weight (oz.) 31.7
Length (Center to Center) 6.625"
Bearings
Length . .88"
Clearance 0005"-.0025"
Material
Standard
0
Moraine 100-A
G T O Firebird 400 and 428 Moraine 400-A
Endplay on Crankshaft .006"-.011"
Timing
9777254 9779067 9779066 9779068 9785744
Intake
22° 23°
30° 31° 38°
. 67° 70° 63° 77° 83°
269° 273° 273° 288° 301°
. . . . . . . . .375"
.407" .407" -
.410" .410" .414" .413"
Exhaust
78° 77° 90° 95°
31° 25° 32° 38°
289° 282° 302°
313°
Lift
.411" .412" - -
.413"
.414"
.413"
.413"
47° 54° 55° 63° 76°
Valve Springs Standard G T O MT G T O RAM-AIR 428 H . O . MT
Pressure @ Length
PSI PSI PSI PSI
Outer . . . . . . . . . . . . . 135-145 @ 1.134" 135-145 @ 1.134" 244-260 @ 1.34" 135-145 @ 1.134"
59-65 @ 1.586" 59-65 @ 1.586" 98-108 @ 1.582" 59-65 @ 1.586"
Inner 99-105 @ 1.114" 118-128 @ 1.114" 118-128 @ 1.114"
28-34 @ 1.566" 48-53 @ 1.566" 48-53 @ 1.566"