1968 Mustang Engine Information – 390 cubic inch V-8 (6.4 L FE V8)
10,494 mustangs were produced and sold with 390 cubic inch engines. The engine came standard with a 490 Autolite carburetor rather than the Holly installed in previous years. 1969 was the last year a 390 would be installed in a Mustang by Ford. All future years used 427’s, 428’s and 429’s for the large block power plants.
Engine Basics
| Year |
1968 |
1968 |
| bbl |
2 |
4 |
| Cylinders |
8 |
8 |
| Displacement |
390 cu / 6.4 liters) |
390 cu / 6.4 liters) |
| Power (hp) |
265 hp @ 4,400 RPM |
|
| Torque (lb/ft) |
390 lb/ft @ 2,600 RPM |
|
| Compression |
9.5:1 |
10.5:1 |
| Bore x Stroke |
4.05 x 3.784 |
4.05 x 3.784 |
Engine Specs (390 cid V8)
Clutch information. All 390 engines with either a 3 or 4 speed have the same clutch specs. The pressure plate is 11.5″ with 12 springs. The disc is 11.5″ with 8 springs
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 end bolts |
40-45 |
| 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 |
30 |
| Flywheel to Crankshaft |
75-85 |
| Oil pan bolts |
12 |
| Valve cover bolts |
10 |
| Carburetor mount bolts |
10 |
| Oil pump |
15 |
| Spark plugs |
|
| Trans. inspection plate |
|
| Water pump bolts |
20 |
| Clutch pressure plate |
35 |
| Upper cam gear |
40 |
| Rocker arms |
45 |
| Main cap cross bolts |
|
Crankshaft Bearing Journal Specifications
Main Bearing Journal (inches)
| Journal Diameter |
2.7484 – 2.7492 |
| Oil Clearance |
0.0008 – 0.0020 |
| Shaft end play |
0.004 – 0.010 |
| Thrust on number |
3 |
Connecting Rod Journals
| Journal Diameter |
2.4380 – 2.4388 |
| Oil Clearance |
0.008 – 0.0030 |
| Side clearance |
0.010 – 0.020 |
Piston Ring Specifications
Comp Ring Width
| Top |
0.077 – 0.078 |
| Bottom |
0.093 – 0.094 |
Ring side clearance
| Top |
0.002 – 0.004 |
| Bottom |
0.002 – 0.004 |
| Oil ring |
Snug |
Ring gap width
| Top |
—– |
| Bottom |
—– |
| Oil Ring |
0.015 – 0.055 |
Piston Specifications
| Code Red |
3.9984 – 3.3990 |
3.9978 -3.9984 (HP) |
| Code Blue |
3.9996 – 4.0002 |
3.9990 – 3.9996 (HP) |
| 0.003 Oversize |
4.0008 – 4.0014 |
4.0002 – 4.0008 (HP) |
| Piston to Cyl. Bore clearance |
0.0018 – 0.0026 |
0.003 – 0.0038 (HP) |
| Piston Pin Bore Dia. |
0.9123 – 0.9126 |
0.9123 – 0.9126 (HP) |
Valve Specifications
| Year |
1968 |
1968 GT |
| Seat angle |
45 |
45 |
| Face angle |
44 |
44 |
| Valve spring pressure lbs/inches |
228 @ 1.38 |
268 @ 1.31 |
| Valve spring installed height (in) |
1 13/16 |
1 13/16 |
| Stem guide clearance (in) – Intake |
0.0010 – 0.0024 |
0.0010 – 0.0024 |
| Stem guide clearance (in) – Exhaust |
0.0010 – 0.0024 |
0.0010 – 0.0024 |
| Stem Diameter (in) – Intake |
0.3715 |
0.371 |
| Stem Diameter (in) – Exhaust |
0.3715 |
0.371 |
