Hi all, just brought my first mustang, its being delivered at the end of the month, it's a 1994 v6 auto, and i was wondering if anyone could give me some ideas for making power with it. Not expecting 500+hp, hoping to go for more low to mid 200s, just to give it a bit more spirit. And if anyone can give me advice on the differential and gearbox, would like limited slip at some point in the near future, and a manual swap is a definite for me. I'm based in the uk too.
Thanks in advance for the help!
You'll want to give this a watch -
Getting 200hp worth of air to pass through single port 3.8 heads without help from a blower is a
big ask. 15+ years ago (and in the USA) the most prudent way to get there was heads and manifold from a Windstar minivan but I think now that's pointless when truck 4.2's are abundant and if you're properly evolved can go under a new edge manifold and thereby under your stock hood without doing dumb stuff.
However given you're across a body of water I suppose heavy parts from wrecking yards are going to be prohibitive.
Look, you already make ~215 ft-lbs of torque (291Nm) and math says if you keep doing that all the way to 5252 rpm that means you make 215 horsepower. The only reason you don't make 215 horsepower is you can't get enough air into, through and out of the engine above ~3000 rpm so torque drops off as rev's climb and horsepower remains down in the 140's.
I am going to assume that since you're in the UK and can't just pop down to a wrecking yard full of American cars, that you probably want to go with things you can do with your existing engine including its existing cylinder heads.
First is exhaust, I see you already have dual outlets - is it dual all the way from the cats or does it come together in that awful 3-way cork the factory installed? If it still uses the miserable stock "Y", pipe it true dual. These are alternate bank fire engines so it doesn't matter if you do true divorced duals, H, X, loop-de-loop, christmas tree shaped... whatever.
Don't worry about headers, nothing to gain there unless you're going long tubes. Then I guess go long tubes. But don't waste money on short headers if you're not doing long tubes.
As for the heads themselves they're a mega bottleneck so if you're staying with the single port heads your only real option is a cam or high ratio rockers.
If cost is a concern then do high ratio rockers since that's a lot less expensive than a cam* and hilariously easy to install. High ratio rockers basically just amplify whatever your camshaft is doing, effectively increasing duration and lift. The total time that the valves are open increases a tiny bit so air has more time to get in & because the effective closed time for the valves becomes shorter (because that moment when the valve just barely opens up happens more quickly) that keeps the air charge moving and has the effect of increasing the tuned peak rpm of the intake runners.
If cost is less of a concern then a performance cam + improved valve springs + stock ratio roller rockers will give you max effort performance on stock heads. Or just order a whole power pack from super six motorsports and go nuts
Again if you're staying single port and
AFTER you do the above stuff porting your whole upper + lower intake manifold is about the only other thing you can do short of finding a pre-84 carb manifold and running 3rd party TBI..
Don't waste a dime (er.. a 10p?) on any kind of throttle body or air filter nonsense or on any "chip". People sell and buy those things because they're easy wishful thinking not because they actually work.
For the differential, if you've got the stock V6 rear axle it is possible to get a 7.5" limited slip - they were stock in 80's thunderbird turbo coupes and in a variety of ford rangers. It's just a clutch type LSD, nothing sophisticated. That's probably the lowest cost option and I don't think spline count changed on the axle shafts.
If you can afford it the coolest axle swaps are either IRS assembly from a Cobra or a complete axle from a 03/04 Mach 1, which gives you LSD, 3.55 gears, big vented brakes and the ability to run quad shocks if you want to, plus it's 40mm wider to better fill out your wheel wells. Either one is mostly bolt-in.. if you aren't too strict about what bolt-in means. I can't imagine what it would cost to get that on a boat though..
Regarding gear ratio choices remember that until you significantly improve breathing on that engine it's not going to do anything for you over 4k rpm so high ratio diff gears on a manual transmission will be a recipe for permanent sadness. 3.27 and 3.45 are available for the 7.5" , I wouldn't suggest going any deeper than that behind an externally balanced 3.8. Even a max effort single port, externally balanced 3.8 is a buzzy mess over 5k rpm.
*(high ratio rockers cost a similar amount to just a high performance camshaft, however you can just bolt them on in an afternoon.. if you're being properly thorough maybe change your valve guide seals while you're in there... change your oil and you're done. Installing a camshaft means you really should do timing assembly and water pump and a ton more labor, gaskets, thermostat, consumables, etc so the total cost by the time you're done is 2-3x as much)
