1968 Mustang Engine Information & Specs - 390 Cubic Inch V-8

1968 Mustang Engine Information & Specs – 390 FE V8 (6.4 L)

390 FE V8 Technical Specs & Data

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
325 hp @ 4,800 RPM
Torque (lb/ft) 390 lb/ft @ 2,600 RPM
427 lb/ft @ 3,200 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

 

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