The Ford V-8 Engine Workshop
5.0 High Output

1985 5.0 High Output, Holley 4V Carburetor 1994 5.0 Mass Air EFI
In the early '80s the horsepower wars were back. Ford's entry in this race was the new Fox chassis based Mustang powered by the newest member of the Small Block family, the 5.0 High Output.

Fed initially by a 2V carburetor in 1982, followed by a Holley 4V carburetor, later by speed-density fuel injection, and ultimately by a mass airflow injection system, the 5.0 inched its way up from around 157 HP in 1982 to 225 HP in 1987. The 1985 and later engines feature roller tappet camshafts and factory short-tube headers; 1986 and later engines feature a ram-tuned intake system.

The 1993 5.0 Cobra featured SVO GT-40 heads and intake manifold, better flowing exhaust, and a recalibrated EEC-IV computer. 235 HP.

5.0 High Output -- Chronology of Changes

1982 -- 157 HP @ 4200

  • Introduction of the 5.0 High Output engine
  • Lighter (120 lb.) thin wall 302 block, with old-style 2-piece rear main bearing seal
  • Reciprocating assembly changed to utilize 50 oz.-in. unbalance flywheel and 34 oz.-in. damper
  • Cast pistons, 8.4:1 C.R.
  • Heads with smaller "high velocity" ports and valves
  • "1973 Torino" profile flat tappet camshaft, duration 260 intake, 278 exhaust, lift of .416" intake, .444" exhaust
  • Double row roller timing chain
  • Aluminum intake manifold
  • 369 cfm Motorcraft 2-barrel carburetor
  • Dual snorkel, high dome cover, low restriction element, air cleaner
  • Cast iron exhaust manifold with a 2" outlet, 2.25" Y-pipe

1983 -- 175 HP @ 4200

  • Same camshaft, exhaust manifolds, and pistons as 1982
  • 600 cfm Holley 4180C 4-barrel carburetor and aluminum intake manifold
  • New block and crankshaft to use a one piece main seal introduced mid-year

1984 -- 175 HP @ 4200

  • Generally the same as 1983
  • Redesigned choke, eliminating heat tubes from the manifolds

1985 -- 210 HP @ 4400

  • Hydraulic roller tappet camshaft introduced. 266' duration, .444 valve lift
  • Revised block (122 lb.) with two retainer bosses for roller tappets.
  • New cylinder heads, revised to allow service removal of the roller tappets
  • Distributor drive gear material changed to be compatible with steel camshaft
  • Forged pistons with low tension rings and thicker ring lands. Compression remained at 8.4:1
  • Holley 4180C carburetor, with improved secondary metering
  • Water pump impeller diameter increased to 4.4" for increased flow
  • Stainless steel tubular headers

1986 -- 200 HP @ 4000

  • Stronger block (126 lb.) incorporating "squared bores" for better oil control.
  • Compression increased to 9.2:1 with flat-top pistons
  • Masked intake valve, high-swirl cylinder heads, casting # E6AE-AA. This head was also used on 1986/91 normal passenger car engines.
  • Roller cam same as 1985
  • First year for multi-port speed density fuel injection, 58 mm throttle body, 19 lbs/hr. injectors
  • Dropped cold start exhaust control valve, header outlet size changed to 2 1/4"
  • New water pump with exit scroll and more efficient impeller.

1987/88 -- 225 HP @ 4000

  • Same Camshaft, exhaust manifolds, and block as 1986
  • Truck casting wedge cylinder heads with revised combustion chamber, casting # E7TE-AA, used through '95
  • 9.0:1 compression forged pistons with valve eyebrows
  • Speed Density EFI with same intake runners, larger crossover duct, and 60 mm throttle body

1989/92 -- 225 HP @ 4000

  • Same block, heads, intake and exhaust manifolds as 1987
  • Introduction of the 55 mm Mass Airflow fuel injection system. Since this system measures the actual air flowing into the engine, high performance camshafts may be used.
  • These engines offer the greatest performance potential of all the 5.0 H.O. series

1993 H.O. -- 215 HP @ 4200

  • Mostly indentical to 1989/92 engines
  • New cast hypereutectic aluminum pistons, lighter weight and greater hot strength
  • Same performance, but advertised horsepower dropped due to new correction method

1993 Cobra -- 235 HP

  • Same cast pistons as 5.0 H.O.
  • Cast iron GT-40 heads
  • Shorter duration, higher lift camshaft
  • 1.72:1 ratio rocker arms
  • Cast aluminum GT-40 style intake
  • 65 mm throttle body, 24 lbs-hr injectors, 70mm mass air meter
  • Special type exhaust manifolds
  • Specially programmed EEC-IV

Small Block Balance Considerations
Small block reciprocating assemblies have external balance. The crankshaft itself does not carry enough counterweights to achieve zero balance. Extra counterweighting is cast into the flywheel and harmonic balancer bring the entire assembly into neutral balance. Early engines use 28.2 oz.-in. external balance, while 1982 and later engines use 50 oz.-in. at the flywheel and 34 oz.-in. at the damper.

Automatic transmission flexplates have a welded-on weight plus a cutaway window on the opposite side. Rivets are used to fine-tune the balance.

28 oz. in imbalance flywheel 50 oz. in imbalance flywheel
Note the small counterweight on this 28.2 oz.-in. flywheel. This flywheel from a 1965/68 Mustang 289 has a 157 tooth ring gear. There are (6) 5/16"-18 pressure plate attaching bolts on an 11-3/8" circle. This holds a 10" clutch. Part # C3AZ-6375-J identified by casting # C6ZE-A and stamped engineering # C7ZE-B. Note the larger counterweight on this 50 oz.-in. flywheel. Ford Motorsports part # M-6375-B302. This flywheel from a 5.0 High Output engine also has a 157 tooth ring gear. This holds a 10.5" clutch, accurately centered with alignment dowels and attached with metric bolts.

5.0 H.O. harmonic balancer Notice the missing section on the rim of this late model harmonic balancer. The part that isn't missing is the counterweight.

When converting from automatic to a manual transmission, be sure to use the correct flywheel bolts. Those specified for use with an automatic transmission flexplate and stiffener are not long enough.
Flywheel bolts D2AZ-6379-B Flywheel bolts B8AZ-6379-A
Current Ford Master Parts Catalogs specify part # D2AZ-6379-B bolts for both flexplates and flywheels. They are not long enough to properly clamp a manual transmission flywheel to the crankshaft. Don't trust 'em. Obsolete but still available part # B8AZ-6379-A is the correct grip length. These bolts come with thread sealant pre-applied.

The cast iron GT-40 cylinder heads may be identified by casting marks shown here. These GT-40 heads are casting # F3ZE-AA. Small block cylinder head casting numbers are found on the underside of the part, between the pushrod holes.
GT-40 casting marks
"GT" is cast in two places on the exhaust side of the head.
GT-40 casting marks
Three vertical ribs are found on the front face of the right-hand head.

Modified: November 7, 2003 37874 hits since June 14, 1997