Part vendors make unsubstantiated claims. Other improvements move the horsepower way up in the rpm's so the car may actually feel slower around town. And since your engine is a system you may not realize the full potential of a particular upgrade until you do something else. All that said, here's a shot at estimates of horsepower increases for some popular modifications:
Underdrive pulleys -- 5 to 10 hp Cat-back exhaust -- 10 hp Headers -- 10 hp H-pipe -- 5 hp K&N-type air filter and remove air silencer-- 5 hp Throttle body -- 5 to 10 hp Intake manifold -- 15 hp Don't forget about gears. No HP increase, of course, but the most performance bang-for-the-buck
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Reggie
Real Racers Don't Street Race
PERIOD.......
'88 LX Hatch With A Little Of This & A Little Of That...... 10.39 @128 MPH Soon to be faster....
Agree with most of the above with the exception of:
Throttle body: No more than 3hp unless it's a 331 or 347. Maybe nothing on a near-stock 5.0.
Headers: Shorties ~5hp, Long Tubes ~10hp.
Intake manifold: Depends on the replacement unit. GT40 good for ~10hp.
Underdrive pulleys: Crank pulley only ~5hp, complete pulley set ~10hp.
1.7 roller rockers: ~5hp.
C&L 76mm MAF: ~5hp (~10hp with cold air kit)
the purpose was to show the comparison of real and advertised hp gains...
Absolutely right. We know that the claimed HP gains from most parts manufacturers are grossly overinflated (the claimed 20hp from the Helix Power Tower probably takes the cake). Fortunately the 5.0 has been around for a long time so the myths have been busted by real dyno numbers.
Maybe the moderators could stick this thread so that Mustang newbies can have a reference when it comes to starter mods. I think it would be fair to say that you would gain about 40-45rwhp from a package of traditional basic bolt-ons consisting of CAI/MAF/TB/pulleys/LT headers/midpipe/catbacks/1.7 roller rockers on a previously bone stock 5.0.
Heads/cam/intake are certainly cost effective but you still need the basic "stage 1" bolt-on stuff to make them work. You could consider H/C/I as "stage 2" either after you've done the basic bolt-ons or do the whole lot at the same time if money allows.
Eagle, I'm sure I could dig around and find some HP gains for heads or H/C/I packages.
Might be sliding off topic here - What about a reduction in chassis flex and better weight transfer?
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'66 Mustang Coupe: V-code Emberglo, C-code 289, Pony interior, typical go-fast parts, T5, 3.80 gear '93 LX 5.0 Vert: Soon to be 5.8 vert '00 F250: Its 8400 lbs, its loud and its fast
Might be sliding off topic here - What about a reduction in chassis flex and better weight transfer?
once again very good this doesnt give u more power but this allows more power to get were u need it by applying pressure in the right areas allowing for better tracktion and less wheel slippage
before i did anything big, i did the suspension. i noticed a huge difference. I went from losing to my friend from the start and by 6-7 carlengths by 3 gear to being in front through 1st and 2nd and only losing by 2-4 carlenths depending on the race. I also did the basic bolt-ons at the same time at the HCI combo, but I picked up most of the parts for very little. It worked out great for me.
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1988 red GT AOD. Mods: Ported GT40P Heads, 3-Angle Valve Job, E303 Cam, Edlebrock Performer 5.0 Intake, 65mm BBK EGR, Professional Products 65mm TB, MAC CAI, 80mm MAF, 24lb Injectors, 255lph Federal Mogul Fuel H.O. Fuel Pump, BBK Shorties, O/R H-pipe, Flowmasters, Dumps, Timing-16*, Shift kit, 4.10 gear, Sub-frames, Aluminum racing radiator, B&M Trans cooler, Pro-Form Upper and Lower Control Arms, Energy Suspension Urethane Suspension Components Recent: MSD 6AL Ignition, Battery Relocation
Very good idea. I'd start by posting some of the proven dyno test done by MM & FF. They've done the heads, intakes and various engine combonations (sizes and levels of builds).
Dave
ignition, engine cooling?, transmission gearing, hell even tire size/type? MAF, I'm sure theres fractions of HP between different performance mufflers even
i dunno... just typing whatever i could think of that others havent
True Horsepower gains for popular mods..... 
