91 Gt Daily... Mid 12's

Discussion in 'Fox 5.0 Mustang Tech' started by sen2two, Jul 18, 2013.

  1. I recently picked up on 91 GT fox body. This is my first V8 car in 10 years, I've been building rotary drag cars for the last decade. I have always had a soft spot for these, so I finally picked one up.

    It's a pretty stock daily driver with a few upgrades. it has a BBK 65mm throttle body, gt40p (Explorer intake manifold?) e303 cam, unknown headers and exhaust, and it has been lowered 1.5". And I have a set of draglites that I will be putting on there. 15x8 in the back and 15x3.5 in the front.

    I'm looking to keep it as my daily driver, but have it still able to pull mid 12's in the quarter. And I would like to do this on a low budget, and keep it mainly factory swappable parts. After reading and searching for hours on end for the last week or two. I have come up with a few needs to get me to that goal on top of what has already been done.

    3 inch aluminum intake pipe with good flowing filter routed to inside the fender for cold air. along with a 70 mm MAF from and 94 to 95 GT Mustang. 24# injectors and adjust the timing. Then finish it off with 3.73 gears. It has 3.08 in there now!

    From what I have read, this should get me into 12.50 range with slicks. Without slicks and really good driving, high12's are doable.

    There are a lot more things that I want to do to it in the future like valve Springs and roller rockers in GT 40 heads, subframe connectors, Ect. Ect. but I'm wondering if my research is correct. because I only know what I have read recently about these cars.

    will this combo work together and meet my goals? Is tuning needed or will the larger maf and injectors handle that?
  2. thats much heavier than i have read else where. is that because it is a 91?

    i also planned on a few free weight reduction tricks. like removing the bumer braces, gut all the extra metal behind door panels, removing the front sway bar, all airbag parts, and possibly the back seats.

    i have read and seen a few videos of 12 second foxs that where factory from throttle body to oil pan. basically gears, intake, exhaust, slicks and skinnies. they where also gutted cars though. whats a gutted fox weigh to make such a big difference?

    i do live in fl. which is pretty much below sea level as well. that helps, lol.
  3. you are going to have to hook it up and drive the :poo: out of it with stock heads on the motor. it will need slicks, axles, an axle girdle, quality upper and lower control arms, welded tq boxes or battle boxes, subframe connectors, a decent clutch and shifter and launch it off the rev limiter. and if you get lucky it will go a 12.99 with E7 heads. if it has gt40p heads it could go mid 12s in the same trim with the explorer intake. if its got draglites on it, it probably weighs 3100lbs w/o you in it. I woundnt bother gutting it. you wont get much out of that, the bumper and door braces are safety items and handling can be dangerous without a swaybar; especially with skinnies on the front. the skinnies also make the cars stop worse than a fully loaded school bus, and that's not an easy accomplishment.
  4. plenty of guys have gotten a stock motor deep into the 12s. its all about prep and weight distribution. definitely pick up a set of gt40 heads if you can score them for the right price. JY pull is the best. you can pick them for about 100 a set. if you have to spend more than 200 on them I would avoid it as by the time you get them worked and ready to install you are nearly into aluminum head territory and they have better castings and RR's already. there is or used to be a thread on corral about launching a stock engined car into the 12 second range. just keep reading. lots you can do to these cars but getting them race ready takes planning and money. I honestly miss my car in stock trim and if I had to do it over again would just find a decent stocker and freshen it up.
  5. so will the car need to be tuned, or will the sn95 maf an 24# injectors do enough to take care of that?

    it breaks up at the top end of 1st and 2nd right now. i think its leaning out. no real way to tell right now though.
  6. pick up the gt40p heads of an explorer, upgrade the valvesprings, put some et streets on her and run 12.50's
  7. I'd be weary of taking too much off the car if it's gonna be a daily driver. Also between the suck a$$ breaks on a fox and the skinnies, have fun stopping that thing on the street. Leave some of the weight for safety stuff, and buy a decent set of aluminum heads and a cam and run 12's all day long.
  8. thats exactly what i was looking for. thank you for the link.

    do you know how much the car weighed after dropping everything?
    Sharad likes this.
  9. I think with gt40 heads, intake manifold, throttle body, full exhaust, injectors and a well selected cam shaft I could see you easily around 260whp with a good tune.

    as fare as weight loss rear seat delete, spare tire, loose that heavy center arm rest, battery relocation.
  10. thats what i am unsure of right now. with the upgrades i have, will a 70mm maf from a 94-95 gt and 24# injectors take care of the "tuning" aspect?

    i been reading peoples upgrades that are similar to mine and i rarely see any tuning mentioned past a maf and larger injectors. a few people adjust timing, but not much else. will my car be safe and reliable without any real fuel tuning?
  11. those stock maf's wont change the injector calibration. to run the 24s you could run a an aftermarket maf, or a 93-95 cobra pcm (which is pointless) or have your pcm tuned if you still want to run a stock 94-95 maf with the 24s. I don't really know why you would want to run a 94-95 stock maf, but its your car.

    if you are going to be launching the car hard on sticky tires I highly recommend subframe connectors (because if you twist the subframe the car will never be right again), tq box reinforcement (because once you rip them out they are a pain in the ass and expensive to fix), decent axles (because if you break one itll likely cause body and other damage and that's more $ to fix, and the tow bill will probably cover axle cost) and if you don't want to hurt the carrier (because that will cost even more $) a good rear end girdle that preloads the caps.
  12. i wanted to run the sn95 maf because i have read they flow much better than the stock 55mm maf and are a direct swap. plus the car is breaking up at the top of 1st and 2nd gear. which i believe it to be leaning out. so i figured it might fix that problem.

    what do you mean by torque box though? i dont mean to sound like a "noob", but none of the other cars i have owned has had one.
  13. you are exactly right about that. but thats why i want the maf and 24# injectors. i believe its leaning out. and im hoping that will correct it.
  14. bigger injectors and an uncalibrated maf wont solve the problem, it will give you others. namely, it will make it run very rich. what makes you think its lean? did you check the fuel pressure? run a wideband on it? even if it has gt40p's and everything works correctly, 19s will supply enough fuel. if its lean enough to be popping and banging out u have other issues. have you checked for vacuum leaks? I had a buddy back in the day with budget deal like yours. a stock shortblock, ported cobra intake, gt40 irons, e cam, exhaust, bigger maf and it air/fueled about 12.8:1 with 19s. it actually slowed down when we swapped out mafs and put 24s in it. that's how I know its not simply an injector size issue. and if it goes lean (like a fuel pump issue) it usually wont do it in the lower gears without going so lean itll fall on its face it in the top of 3rd and 4th because that is where it has the most load and needs the most fuel. at any rate, I would suggest diagnosing the problem before throwing parts at it.
    f8tlfiveo likes this.

  15. No problem! I didn't weigh it, but it was probably around 3050 without me.
  16. So far clement has given you the best advice. Take it and run with it...
  17. i agree. i think i will check fuel pressure tomorrow and go over the basics. what should i be at, 39psi?

    also, i think the fuel pump has been upgraded. its much louder than any stock pump i have ever heard. its about as loud as the walbro 255s i have used in other cars.