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, 65 mm TB, 24# injectors, 70 mm MAF and a recalibrated EEC-IV computer. Conservatively rated at 235 HP (was actually around 265 FWHP).
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
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 the 5.0 H.O. series
In stock trim, the small 55 mm MAF & revised camshaft actually limited breathing, so it was no longer producing 225 HP.
1993 H.O. -- 215 HP @ 4200
Mostly indentical to 1989/92 engines
New cast hypereutectic aluminum pistons, lighter weightand greater hot strength
Hi-torque, mini starter
Advertised horsepower dropped due to the incremental changes.
1993 Cobra -- 235 HP
Same cast pistons as 5.0 H.O.
Cast iron GT-40 heads
Shorter duration, higher lift camshaft
1.7:1 ratio roller 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. 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. 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.
Some corrections and additions... additonal info provided by FoxChassis
1982
Rotating assembly imbalance changed in '81, not '82.
1984
When automatic (AOD) transmission was ordered, the H.O. engine's induction was CFI instead of 4V and HP was 165.
1985
Same AOD/CFI combo as '84, and same 165 HP, but only early in the year. This combo later received the same exhaust system as the 4V/T5 combo and HP jumped to 180.
1987 (and later)
Pistons also had a slight dish.
1988
Camshaft changed slighty late in the model year to reduce valvetrain nose. New part number for the cam. Power dropped slightly but was not reflected in the rating.
1991
Cam changed again (dowel) and got a new part number. Specs remained the same and no power change.
1992
Hypereutectic pistons late in the year.
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GT40 heads have F1ZE, then F3ZZ, and finally F4ZZ casting number.
Your welcome buddy. I'm pretty sure this is the most accurate information I can find right now, and if I find proof of anything else being better I'll be sure to post it up too.
so in 86 ford introduced the flat top pistons.are these found on 87-88 motors too? Is it possible to use the gt 40 heads or aftermarket heads whith these flat pistons?
Most HO motors produced between 87-93 were RATED at 275-300 torque. Remember, this is just a rating, it is not an accurate measurement of torque. 86- and earlier were rated at 245-260 I believe. For instance, the 2005-08 Mustang GT is rated at 300 horsepower. You put it on the dyno, it would probably only put out 270-75 horsepower. The 300 hp rating was a selling point. Some cars are over-rated while some are under-rated. It's a hit and miss on the actual numbers when a person buys a new car.
How come the 94-95 had higher hp and torque ratings than the 93's. Is it cause of the electric fan and 70mm maf?
Because Ford lied to put it simple. Ford dropped the ratings in 1993 so people would not be upset with a lesser HP rating when the new design came out. 1993 and 1992 where the same except Ford put the new hypertonic pistons inside the block in '93.
so in 86 ford introduced the flat top pistons.are these found on 87-88 motors too? Is it possible to use the gt 40 heads or aftermarket heads whith these flat pistons?
No, 1986 was the only year to have these pistons. I have heard people getting away with GT40 heads on 1986's, but it is not the norm. (I personally do not know anyone who has done this...I have just heard it's been done.) 1987 and up are notched and heads can be swapped right on.
93' Cobra was like 265 hp, even though they rated it at 235.
