It provides drivetrain stability and reduces flexion and vibration

 

Wow,
That car your building looks like fun. Is that a 600cc street bike engine? I'll bet it will get with the program. Is teh flaming Riiver unit for your Mustang or the project car?

 

Yes, it's basic structural support. It's not usually highly stressed. Several VMFers have bought and driven cars for some time without one. Not a good idea, but the rack installation should be a sufficient substitute.
I ran into a guy with a '70 who has adapted bars from a 87-93 convertible Mustang to his. One goes from each end of the radiator support to a metal tab on the crossmember, then two more on the back (another tab) of the crossmember that run to each torque box. The end result is without an engine, the engine bay viewed from above would be filled by an "X". Probably not the best description but stick your head under one of the 87+ Fox convertibles and you'll see what I mean right off.
It would seem a simple enough project, but I'm not sure whether it's worth the trouble. The Fox and the older Mustangs differ quite a bit in unibody and front suspension design.

 

Yep, Honda 600cc bike motor with Haltech programmable EFI. I've finally found a purpose for my latptop /forums/images/icons/smile.gif
The car goes 0-60 ~ 4 seconds. I haven't attempted top speed as of yet, but once we get the new Torsen differential and bracket in place, we'll be testing in a couple weeks. We still have to build a body, tune the suspension and EFI, and then we'll be taking some runs.

The rack is for my car. The SAE car has a center steer unit shown here. This view is from the front of the car, looking down on top of the pedals/steering. The steering is dead on accurate as you can see from the box, and the car is only 500 lb, so it's very easy to steer. It's only 1 turn lock to lock. When the only part of your torso that you can move is your wrists, you need that quick ratio!

 

I'm planning on ditching my cross member. I'm putting struts on my front end that'll connect to my roll cage. I think I can run them underneath the fender so I can save engine compartment room. In fact, it looks as if the A-pillar bar of the cage is perfectly lined up so the struts will go through the firewall just outside the inner fender.

The struts should hold the front end together just fine. I'm going to run them as close to the inner fender as possible for tire clearance and because I'm also going to use them as mounting locations for the top of my coil overs. I can't stand those damn shock towers, they're in the way. If I can get a good enough angle on the shocks, I'll be able to completely eliminate the towers and weld in flat sheet metal.

I'll have some say in the mounting angle of the shocks because I'm building my lower control arms and I can mount them very close to the spindle so I can move the upper mount further out toward the tire.
I know you do a lot of custom work. If you want more info on my suspension, PM me. I'm building my uppers, lowers, and a rear coil over suspension.

 

It is just support for the chassis flexing. The Falcon/Comet doesn't have that lower crossmember even though they are pretty close to the same car as a Mustang. My theory on that is that they felt they needed the additional support on a "sporty" car that would get driven harder. Also the Falcon/Comet's shock tower braces are welded to the shock tower and cowl where the Mustangs are bolted in. Mustangs have a slightly narrower engine compartment so they needed to be able to remove the supports to be able to get the engine in/out.

If you are already welding together a suspension, why not just use one of the Mustang II crossmembers that so many people are making these days? It makes getting parts for the suspension easy a few years from now when something breaks and you don't have time or inclination to make a new one.. You can buy the crossmember for $350 or you can make your own if you are so inclined. I bought the crossmember alone for my Comet and am piecing the rest together from various speed shops/junkyards. If you do the tubular arms with the crossmember you don't need strut rods and it sure looks a lot cleaner.. If you want to see pics of this going in you can click on the link in my sig, go to the Comet and they are in the last few pages of pics.

PS your Formula car looks like it is shaping up pretty nice. The modern 600cc sportbike engines are just amazing these days.. I read in one of the motorcycle magazines that Suzuki is showing a 4 wheeled 2 seater based around a gsxr 600 powerplant to gauge interest in a car like that.

 

Mike old buddy....

Were you planning on installing the Mustang II rack in front of the front wheels? The TCP, Taurus and GM J car all mount behind the wheels.

What this means is that you would need to turn the Mustang II rack's steering wheel in the opposite direction than in other cars. IE to go right you would need to turn left.

Sure it would impress your friends but it would be dangerous!!!

 

No problem...so I'll mount it behind the wheels. I see how it works. Are you saying I should get the Omni rack?

 

Mike, I haven't followed all your posts. How are you mounting the inner lower control arm pivot points. The lower cross member was a production fix (Falcon to Mustang) to try and stabilze the lower control arm mount under cornering loads. The factory TransAm's had a modified cross brace than tied the factory points into the lower control arm pivots. Since you are welding/fabbing, I would think a similiar setup would be benefical (and less stress on the rack. Bob.

 

Bob,
You haven't missed anything, this is my first post about building control arms and setting up R&P. Since I've been working on the SAE team and doing a lot of fabricating, I've acquired the skills to do it. I've even got access to a TIG, full machine shop including a Bridgeport and a CNC machine. I'm not going to make anything great...I was just thinking of copying TCP's design*. I've sourced the steel tubing and Kevlar injected rod ends, I just need to figure out how to incorporate the ball joint.

* I want to eliminate the strut rods, so I was thiking of building a lower arm with two inner pivots. I think I'm getting ahead of myself a little though. I could probably do it, but I don't know if it's worth it. That's why I'm also considering a MII kit. Thing is, I don't mind cutting up the car (ie roll cage, MII kit) but I don't want to start doing one offs like designing my own control arms because, although I can physically do it, I don't trust that it'll be good enough to drive on every couple of days. If this were a dedicated race car, I would try anything, but I don't want to end up with a wheel flying off on the highway. One I get more practice and another car in the future, I'll try my own designs. As for now, it's either a copy of TCP or a MII kit.

If I don't do a MII kit, I'm going to do the brace as you suggested.

 

I'll that some flack for this, but remember that a Mustang II is just that (this is from a low period of Ford design/quality built for Lopo 4 bangers). When most of the rodders use the design, the parts are so heavily upgraded that it's not a MII anymore. If you don't need the fender clearance, I personally wouldn't do.

I don't think I would fab a double pivot lower control arm either. Have you checked out the Coleman catalog. They sell a number of circle track arms (upper and lower) cheaply. Most of the uppers come with 6" mounting whole centers, but I'm not sure that's a big issue to modify. Welding in mounting tabs for the lower spring perch should't be to difficult.

Pay attention to the difference between a front steer vs. rear steer rack and good luck. Bob.

 

The Mustang II is just a convenient standard for where to put the bolt holes and how the spindles mount up. Everybody runs tubular stuff which won't even bolt up to an actual MII since the lower control arm mounts on the outside of the crossmember instead of inside for increased rigidity.

The only reason it is called a Mustang II front suspension anymore is since it uses MII rack, spindles, springs and shocks... And actually not always even that since I have seen kits that let you choose which side of the crossmember to put the rack on so they are obviously using different racks for the behind-the-wheels type.