5 Components to a 12 Second NA Mustang GT

[Bill Putnam]

Although this is old news to most now but I get asked for this document all the time so here it is.

Let me preface by saying this article is basically geared towards drag racers not your average looking for 12s on street tires with no real changes to the car. No that it can't be applied to someone looking for that but this for the racers out there wanting to hit this goal and aren't afriad to work for it.

1.) Power - if you listen to some old school drag racers they may say you need at least 300+RWHP to hit 12's in most cars. In some heavier cars that may be true but fact is suspensions are more refined this days and cars don't weigh 4,000lbs. Most PI headed cars will hit the 245-255RWHP mark with basic mods (Pulleys, Timing Adjuster or Chip/Tune, O/R H or X, K&N or other type of high flow filter, and although not a power mod...gears 4.10's or 4.30's..Don't Fear the Gear!). For a bolt on GT this is enough power to get the car into the 12's after you follow the remaining steps. Keep in mind the more power will make it easier to reach your goal or help offset more weight (see next section) such as a convertible.

2.) Weight - Your basic 5 speed coupe without driver weights 3,250lbs (99-04 GT, 01 Bullitt, 96-98 GT add 100lbs). So with an average driver weighing about 180lbs that puts your race weight at 3,430lbs. At that weight and a power to weight ratio of .075 you would need 258RWHP to hit 12's. Power to weight is the power of your car (rear wheel) divided by race weight of the car. Using my car when I broke into the 12's the first tiem I was making 246RWHP and had a race weight of 3,250lbs, which worked out to a .075 power to weight ratio or .075RWHP per pound of the car. From what I've seen a car can get into the 12's with a .075 to .080 P/W ratio. So if your race weight is 3,430lbs then 3430 X .075 = 257.25RWHP. As long as you keep this ratio in the .075 to .080 range you are fine. Plus keep in mind you can drop weight instead of adding power. An example of this is a car with a 3,000lbs race weight could break into the 12's w/ 225RWHP (close to stock power of a GT).

Now I'm sure some of you are asking about weight reduction. Basic weight reduction would be rear seat delete, removal of spare tire/jack/tire iron and these would knock a good 70-80lbs from your car. Add a set of welds or light weight race wheels and you are looking at another 60-80lbs. For more specifics on weights and more ideas look here.
http://www.modularrevolution.com/forums/weight.php

3.) Suspension - I feel that this component has the most leeway so to speak. I've seen near stock suspension cars get good weight transfer. I honestly believe a car that meets the other requirements could hit 12's on the stock suspension. However those of you that want to get an edge should read on. First thing I would do is look at springs since most of us want a better stance but still weight transfer. For that look at fox body 4cyl springs I usually look at the junkyards for these but most buy stock replacements at a local shop (avoid Moog brand though they are taller than stock specs). For the rear end I go with fox body v8 rear springs cut anywhere from 1/4 to 1 coil to level out the car. Just keep in mind that it's easier to cut too little than too much spring and have to start over with another pair of springs.

Next I would highly reocmmend a pair of sub-frame connectors welded in to tie the chassis together. Hard launches on slicks will twist the body and this will help keep it straight. Last piece to really help out is struts, I went with Lakewoods because they are readily available and affordable but adjustables can be used as well if you have the budget for them. 70/30's and 90/10's both work well and I stick with fox body specific struts since the car is lowered. Fox body specific springs are 3/4" shorter than stock SN-95 springs so the lower Fox body specific struts are shorter. There are some companies that now make shorter struts specifically for lowered SN-95 cars.

4.) Traction - I'll cut to the chase here and just skip over street tires and drag radials and go right on to slicks. Not that it can't be done on these tires but it will take more power, more patience and much more writing on my part so we'll stick to slicks. Cars in this weight range and power level only need a 26x8.5x15 ET Drag for traction. It's close to stock tire height and is more than enough to make our cars hook at the track. A better suspension will result in better 60 foot times but even on stock suspension a good burnout on slicks will not spin unless the track is poorly prepped or fluids are on the track. Some people opt for cheap steel wheels which I don't necessarily recommend since you are keeping extra weight on the axles by doing so. This opens you up for possible breakage so I would go with a weld wheel instead even if it's a pair of used ones for track only purposes. Regarless a 15x8 with 5 on 4.5 bolt pattern and 5.5" backspacing will fit perfect, or if you insist on a winder tire like a 10" then a 15x10 with the same bolt batter and 6.5" backspacing will also work on these cars.

5.) Practice - This is one component you can't buy at the store. You can't learn it from a text book and you can't ask your friends about it. You simply have to get out there and do it. I'm not saying everyone should be like me and hit teh track every test and tune but don't expect to make one trip and bingo your in the 12's. I race on slicks for 3 months before hitting my first 12 second pass. Going on slicks alone was a big change that I had to adjust to before I goet the hang of it and learned to shift better, etc... Take your time, get comfortable in the car and have fun with it. Do that and you'll achieve your goal.

Now that you know the key components to getting into the 12's you just have to keep it all together. In the above situation I would also highly recommend an aftermarket shifter just to help keep the transmission alive longer. The biggest weakness is the differential and axles. Not to say they can't take some abuse because they can, mine went almost a full year of launches on slicks before breaking. I would look at a set of 31 spline axles and a Ford 31 spline differential beefed up to keep the back end in one piece or a spool if you can live with the cons of such a bullet proof piece (see spool article).

Bill