1968 Mustang Engine Information – 428 cubic inch V-8 (7.0 L Cobra Jet V8)
The 428 CID engine was developed in 1966 to replace the 390 used in the larger cars. 1969 was the first year that Ford installed a 428 cu inch engine in a Mustang. In designing the engine, the engineers used some parts from the 427, added some new parts and produced the 428. The engine was an awesome performer and is still prized as a premium muscle car engine today. They are getting harder and harder to find.
The 428 Cobra Jet engine used a nodular cast iron block and crankshaft, forged steel piston rods and aluminum pistons. The 428 Cobra Jet used an external oil cooler as well.
During the mid-1968 model year, a drag racer for the street could be ordered with this optional 428 cu in (7.0 L) Cobra Jet engine which was officially rated at 335 hp all of these Mustangs were issued R codes on their VINs.
Engine Basics
Year |
1968 |
bbl |
4 |
Cylinders |
8 |
Power (hp) |
335 hp @ 5,400 RPM |
Torque (lb/ft) |
440 lb/ft @ 3,400 RPM |
Compression |
10.6:1 |
Displacement |
428 cu / 7.0 liters |
Bore x Stroke |
4.130 x 3.984 |
Engine Torque Specifications
All torque specifications provided in this table are those recommended by FORD. If you use special bolts, follow the torque specifications provided by the manufacturer. I recommend that you use the 3 step torque technique where you torque down the bolts in three equal steps. Once you have reached the maximum recommended torque setting, go around one more time. Do not torque in a circular pattern. Always torque cross to cross.
Head bolts |
80-90 |
Main cap bolts |
95-105 |
Rod bolts |
53-58 |
Intake bolts |
32-35 |
Exhaust manifold bolts |
18-24 |
Harmonic damper |
70-90 |
A/C Compressor mounts |
|
Engine fan |
|
Motor mounts to engine |
|
Bellhousing bolts |
25 |
Trans to bellhousing |
|
Flywheel to Crankshaft |
75-85 |
Oil pan bolts |
12 |
Valve cover bolts |
10 |
Carburetor mount bolts |
|
Oil pump |
15 |
Spark plugs |
|
Trans. inspection plate |
|
Water pump bolts |
20 |
Clutch pressure plate |
35 |
Water pump |
|
Upper cam gear |
40 |
Rocker arms |
45 |
Main cap cross bolts |
40 |
Crankshaft Bearing Journal Specifications
Main Bearing Journal (inches)
Journal Diameter |
2.7484 – 2.7492 |
Oil Clearance |
0.0010 – 0.0020 |
Shaft end play |
0.004 – 0.010 |
Thrust on number |
3 |
Connecting Rod Journals
Journal Diameter |
2.4380 – 2.4388 |
Oil Clearance |
0.010 – 0.0030 |
Side clearance |
0.010 – 0.020 |
Piston Ring Specifications
Comp Ring Width
Top |
0.0774 – 0.0781 |
Bottom |
0.077 – 0.078 |
Ring side clearance
Top |
0.002 – 0.004 |
Bottom |
0.002 – 0.004 |
Oil ring |
Snug |
Ring gap width
Top |
0.010 – 0.020 |
Bottom |
0.010 – 0.020 |
Oil Ring |
0.015 – 0.035 |
Piston Specifications
Code Red |
4.1284 – 4.1290 |
Code Blue |
4.1296 – 4.1302 |
0.003 Oversize |
4.1308 – 4.1314 |
Piston to Cyl. Bore clearance |
0.0015 – 0.0023 |
Piston Pin Bore Dia. |
0.9752 – 0.9755 |
Valve Specifications
Year |
1968 |
Seat angle |
Intake 30, Exhaust 45 |
Face angle |
Intake 29, Exhaust 44 |
Valve spring pressure lbs/inches |
268 @ 1.31 |
Valve spring installed height (in) |
1 13/16 |
Stem guide clearance (in) – Intake |
0.0010 – 0.0027 |
Stem guide clearance (in) – Exhaust |
0.0015 – 0.0033 |
Stem Diameter (in) – Intake |
0.3715 |
Stem Diameter (in) – Exhaust |
0.3710 |