1991 LX Suspension MODS

[Chuck Boone]

I have some questions regarding Fox Mustang front and rear suspension, transmission, exhaust, and structure that some of you out there may be able to answer.

I'm building a '91 5.0 LX and am following some of the modifications in a book, "Mustang Performance Manual, Vol. 2" by Wm. Mathis.

Front Suspension:
The book details modifications the K-member including moving it forward 5/8" in the car; moving the motor mounts back 1 5/8" (resulting in a net 1" engine set-back); moving the lower control arm pivot points inward 3/4" and moving them up 1/4" in front and 3/4" in the rear; using '78 T-Bird control arms (3/4" longer than Mustang control arms); and milling .250" off the steering rack mounting bosses.

The end result is better front-to-rear weight distribution, more favorable camber change during spring compression, increased caster, improved Ackerman steering, and increased anti-dive. Have any of you done this modification, and if so, did you have any problems with header-to-firewall clearance or clearance problems around the bellhousing caused by moving the engine back 1"?

Transmission:
I will use a Tremec T56 transmission and a shortened drive shaft. I realize that the shifter will be a little further back on the transmission tunnel. Do any of you have experience putting a T56 in a Fox Mustang?

Rear Suspension:
I will install a Steeda 5-Link rear suspension. It involves relocating the upper trailing arm pick-up points on the chassis and installing new upper trailing arm mounting brackets on the axle housing tubes outboard of the diff center section. It includes a panhard bar. There is no room to run exhaust tubes over the axle housing. Steeda recommends using turn-downs or side exhaust pipes.
I bought a Bassani side exhaust system that is designed for '79-'93 Fox Mustangs. The intermediate pipes enter and exit at the front end of the mufflers, and the side pipes exit the car at 45 degree angles in front of the rear wheels.

It appears that the side pipes will interfere with sub-frame connectors. I'd like to buy or fabricate subs, but do not want to do so if I can't use them. Do any of you have experience with the Bassani side pipe system and subfame connectors?

Structure:
As I said, I want to install some sort of subframe connectors on the car. I also plan on putting in a roll cage with bars coming off the top rear hoop that will touch down at the points where the upper and lower rear trailing arms attach to the car; and upper and lower bars on each side connecting the rear hoop to the front hoop (the hoop that goes up the A-pillars and over the windshield).

Will the roll cage take the place of subframe connectors and adequately reduce flex in the Mustang's flimsy structure?

I've torn the car down and am ready to weld the cage in, paint the car, and put it back together using the new and modified parts. I thought it would be smart to see if anyone else has done the same mods to their cars, and if so, hear about any problems they encountered. Thanks for your input.

ChuckB

[NO SLO PK]

That's a lot of questions. I own the same car, and happen to own the same book you have quoted. IMO, I think some of the information in that book is dated since more advanced suspension components have become available after the book's publishing.

These are my suggestions on some of the ideas in the book:

Engine set back -

This is a serious mod, usually performed for an all-out road race effort. I can't think of anyone here who has done this. If you want better weight distribution, I'd start by using aluminum heads (cuts 50 lbs. off the nose) and relocate the battery to the hatch area. Also consider a tubular k-member and a coil-over conversion with tubular arms -- not only will this reduce front end weight, but also the coil overs and tubular control arms will reduce unsprung weight.

Rear suspension -

Steeda makes excellent suspension components, but if you are going to spend the money (and it sounds like money is not an issue) I would look seriously at converting to the Cobra Mustang's IRS (independent rear suspension). Specific years to look for are Cobras from '99, '01, and '03. With IRS you can use a rear-exit exhaust and won't have to worry about CO poisoning.

Structure -

I would install both the cage and the subframes. The subframes tie everything together and can help prevent the floor pan from separating in the seat area.

Again, just my suggestions based on a little reading, research, and personal experience. Hope this helps!

Russ

[Miss Mischief]

This is a serious mod, usually performed for an all-out road race effort. I can't think of anyone here who has done this. If you want better weight distribution, I'd start by using aluminum heads (cuts 50 lbs. off the nose) and relocate the battery to the hatch area.

Those Mods The Heads Battery Relocation and Bealive this Or Not Lead weights Under the Rear seat Gain Positive balance and achieve Better Take Off, and With the Right Rubber Is Much less a hand Full of Car In Cornering. I got the Lead weights Idea from a SVT wrench Who Weighted My cars Nose "Front wheels" and Back side "Rear wheels"at a Truck weighting station He then Bolted Flat Lead weights Under The Rear seat even with the sleeper 15" Frost white rims I can Get a whole Shot in First with only a slight bark and very Low to No Nose lift.