Performance upgrades 1989 mustang gt conv

[sterah1]

I recently purchased a 1989 mustang gt convertable. The car has cat back flowmasters, 4 wheel disc brakes, and bracing bars in the hood and elsewhere to compensate for the convertable. It also has been converted to a 5 speed. The existing rear end is 2.73? which I plan to upgrade to a 3.55 or a 3.73.

I appreciate some suggestions on how to add about 50 horsepower for the least amount of money. I have done some research and am considering the following:

1. Long tube headers and H pipe- Does my stock catalytic converter stay in the same place.
2. Cold air induction system
3. 76mm mass air meter. Do I even need this?
4. Typhoon EFI intake manifold
5. Power throttle body What size?
6. Underdrive pulley

Should I add or take away any items? How much horsepower would I gain? --Thanks

[speedfreak]

Your rear gears are very likely 2.73s with 3.08 being optional for 5-speed cars. I'm not sure, but automatics may have been available with 3.27s also. If you drive alot on the highway at 55mph+, then 3.55s might be ideal, but you have a heavier 'vert, so I'd lean toward the 3.73s. There is only like a 200rpm difference at 70mph in 5th.

For the mods you listed:

1. Long tube headers are great. They are harder to install and you need a special H-pipe. If the H-pipe is not custom made with cats, I dont know of an aftermarket one that has them.

2. Dont bother with a "cold air" intake unless you want it for looks. Your stock one already is a cold air intake. At the most get under the fender and pull out the silencer box. Maybe get a K&N drop-in filter.

3. A 76mm MAF will in fact help. Your stock one is smaller than the throttle body.

4. Typhoon intake will give the most gains, but will really shine with a TB, MAF, and cam. Doing a port clean up on it will help also as they are a little lower quality than Edelbrocks. Also worth mentioning is a Cobra or Explorer intake. The Explorer flows the same as the cobra and can be had for less than $250 used.

5. 65-70mm TB will be about right. 75 is better matched to a stroker or blown car.

6.Underdrives are a good idea, but its possible you'll have ide-speed charging problems since the alternator will be spinning slower. Dont plan on an electric fan unless you get a 130 amp 3G alternator conversion.

You might also consider an E-303 or B-303 Motorsport cams. They seem to work well with stock heads and provide some room to grow. The biggest bottleneck in your engine will be the E7 heads.

I suck at guesstimating power, so I'll just say that with the mods in my sig, I expect 270rwhp which is equal to your crankshaft goal. Keep in mind I have heads, but not an intake.

[stang_racer20]

Sounds alright to me, but beware of the alphabet cams as they tend to idle funky. TF Stage 1 is better IMO, but of course you wont see nothing big with those stock heads on there. I'd say maybe 250 -260 bhp.

[351wStang]

Ya the Trick Flow cams are nice. I to would suggest the Trick Flow stage I cam over any alphabet cam. May just be careful of the .510 lift at your exhaust valve.

[Drevil]

1. No when using long tube headers you'll need a different h-pipe. You have the choice of going with an offroad h-pipe or a catalytic h-pipe. There are a number of companies that sell short versions of catalytic h-pipes for long tube headers.

2. Cold air induction system... Like somebody just said, a CAI kit wont really do much for power. On my 92 i felt a slight increase in power in the mid range but nothing worth really mentioning. Definately get rid of the silencer behind your stock airbox and at the very least buy a K&N filter. IMHO for the price of a regular K&N panel filter you might as well just spend another $10-20 and get an ebay (procarparts) CAI kit. I bought one for my cobra and its actually better quality than the MAC cold air kit i had on my last car.

3. 76mm mass air meter.... On my 94 Cobra i DID notice a power gain from adding a 75mm Pro M MAF and a 65mm TB at the same time. I've never owned any other MAF's but from what i've heard about some other brands i'd suggest sticking with Pro-M.

4. Typhoon EFI intake manifold... Won't add much power without changing the heads but every little bit counts. I'd suggest waiting until you are ready to goto aftermarket heads and a cam for this mod. (do all three together)

5. Power throttle body... Stick with 65mm unless you are going to be "highly" modifying the car, or if you are adding some type of forced induction (supercharger/turbo). If you are going with a set of high rpm heads, cam, intake then go with a 70mm, but for a bolt on engine dont go over 65mm.

6. Underdrive pulley.... Other than gears, this is probably the best bang for the buck you can get. Definately get yourself a set of underdrive pulleys!!! I've heard of people having charging problems in the past but have never actually known one person who has had this problem. I believe its more of something that will make a problem worse. Such as if you have an alternator/battery that isnt in good condition adding underdrive pulleys may make that problem noticable.

Definately go with a set of 3.73 gears, you'll love them!

Hope that helps

[sterah1]

Thanks for the help. Your replies are much appreciated.