Mustang II Crossmember Questions

I bought a universal MII cross member from Heidt's. I have a F350 (not an F1-200). My frame rails are about 1 inch taller than the F100 frames. I've tack welded the cross member in place and notice that the member sits below the top of the frame rail about 1 inch. I'm wondering if that lower Angle Arm pivot point is too low for the correct geometry. Should I channel the frame to move the cross member up? Or Drill a new hole 1 inch higher, and fill the old one?

Question two for you Gurus. The cross member also interfers with mounting the stock Y back in place. Any suggestions there?

 

The problem I would see with redrilling the "A" arm pivot hole higher is that it would throw off the relationship of the steering rack/tie rod to lower arm a bit.

Since you already have oil pan interference, raising the crossmember would seem to aggravate that situation. Have you tried mounting the lower "A" arm, leveling it (to simulate ride height), putting the spindle in place and seeing where that puts the center of the wheel/tire combo you are using?

What I am getting from your description is that you think the spacing between the upper and lower "A" arms is too great...........Once you determine the ride height with the lower arm "where is"......you may decide you need to lower the upper "A" arm mount instead.

Ray

 

I'll post a pic real quick of the gap, because from memory I think it's a little over 10 inches. But, you're right Ray, I'm worried the gap between the upper and lower angle arms would be too great. Hang tight and I'll post the pic.

 

Everything you should need to know when fabricating your own kit.

http://www.jalopyjournal.com/forum/showthread.php?t=70073

Geometry in this case is out the window. At best you should not disturb the relation between the rack and the lower control arms if you want to minimize bumpsteer. Your choices to get close to standard MII geometry is to section the crossmember up into the frame or lower the spring pocket.


You need the rear trans mounts from a Chevy 4X4, they are taller than the stock Ford mounts and a spacer for the front mount should be sufficient to raise the engine an trans for rack and pinion clearance.

 

My other concern is that the upper angle arm mounts are at 5 degrees camber (I've been under the impression that they needed to be 3 degrees). Thanks for you're input.

 

Thanks for the link.

We were also considering fabricating some type of plate to raise the mounts from the stock positions up to get the necessary clearance. It would be ideal to keep the stock motor/tranny mounts so that I know the engines set in place correctly, but, If I have to get all Chuck Norris on my truck I will.

Thanks again guys!

 

Brush up on some of your terms before you start making changes.

Alignment specs, Caster and Camber have to do with the relation of the spindle and tire to the road surface. What you are measuring is anti-dive. and five degrees is light, but not out of spec.

 

That's a Heidt's crossmember kit? Wow, have their standards gone down.

 

What looks odd about the cross member?

 

I think that you may be stuck lowering the spring pocket/upper control arm mount. You can correct the anti-dive angle in the process too.

You may be able to notch the cross member a bit for pan clearance, but the limit is going to be the rack itself. You will likely have to move the engine and trans assembly up a little. It looks like there will be room.

I believe that, if the control arm relationship is not preserved, in this case mounted farther apart, that you will have some funky, if not dangerous handling. Both wheels will go way out of proper camber when the body rolls in a turn.

 

The rack mounts are pretty basic looking, not as clean as they used to be. And the shock towers used to be a spun cone shape, they look more like Fatman parts now.

Please don't change the anti-dive angle. Your truck will be nose heavy and to lessen the anti-dive angle will void what anti-dive properties you may have.

 

Yup, if El Polacko says it is good, then it is good.

 

Thanks for the responses. I just want to make sure that I've got all my ducks in a row before I start to screw things up. I've read A LOT over the weekend and have come up with slightly different numbers. Probably opinion more than fact.

The distance from the lower angle arm horizontal center line to the top line of the shock tower should measure 9 to 9 and 1/4 of an inch in front, and 8 and 1/2 to 8 and 3/4 inches in the back.

Are those accurate numbers?

 

Sounds about right. The difference may be in the varying anti-dive settings per application.

 

As you know, New owners

 

I did know, wow. Increase profits by cutting corners, the new American way!

 

I'm thinking you need your upper A arm and lower, perpendicular from each other,in other words if you raise the upper too high when spindle is installed it may affect the up and down motion and cause the wheel to move in and out as you raise the wheel.Just my opinion.

 

I'm sorry the A arms have to run parallel from each other...Man i gotta go back to school

 

I think this is really important,mount your spindle on the A arms and set them on the frame and level the lower and then check the upper,should be level as well..

 

cutting corners. I've been out of the loop for a while whatever happened with these setup breaking?

 

Hey Mr, 33_chevy, do you have practical experience in setting these front ends up?

I have over 20 years of experience with the Mustang II suspension. I have set up and repaired more of these than I care to recall. I appreciate you trying to help, but the advice you are giving isn't helping anyone here.

Steve, Gary Heidt made good on what he had to. I did also notice after our heated discussions the fractured corners got a spot of weld and the tubing size on his control arms was upgraded. Other than the centered (not caster offset) upper control arm mounting points, his kits were becoming well made. Well, except for that single shear issue on the lower control arms.

 

Wow!...I'm sorry,but am i completely wrong by saying the arms have to be parallel from one another...By the way i have also installed a few,not near as many as you though.Again sorry for my 2 cents on the issue..I will but out..

 

Not trying to get your goat, it's just that too many cooks can spoil the soup so to speak.

I do more than install, I design, tune and adjust to my customers specifications. I challenge you to go out and look under cars that have not been modified. Notice the relation of the lower control arms to the earth. Rarely are you going to find control arms set up level to earth.

The reason why is for higher roll center and a more generous camber curve. To set up the arms level usually pulls high positive camber at rebound but lazy or little negative camber under compression. This tends to roll the outside tire under (higher slip angle) under body roll lessening grip on the outside tire while increasing grip on the unloaded tire, which does little for helping with positive steering control.

 

So. The upper and lower angle arms shouldn't necessarily be parallel to one another?

And the lower control arm also shouldn't necessarily be parallel to the earth?

I've moved it a little closer to the wheel well center, and am going to do my final welding this week. I appreciate all of you're input thus far guys!

 

Nope, parallel upper and lower arms is not good in this situation nor should the lower arms be leveled.

 

Hmmmm. Vey interesting.


In this situation, knowing what you do, what would your non-hands on guess for setting up the control arm angles? Both lower and upper. And why?

Just trying to learn.

 

It's related to the camber curve. Making the arms more parallel moves the instant center out farther toward infinity. A longer instant center slows the camber arc which leads to more understeer. In the case of the Mustang II suspension to spread the control arms to make them level to each other does some weird things with compression and rebound camber angles. In most cases I can model the wheels camber negative at full droop, this drags the inside tire around the corner like a 70's MOPAR and at full compression there is little or no negative camber. It doesn't produce a smooth and usable arc.

Also the more level the lower arm is moves the roll center lower. Lower roll center induces more body roll.

I know these cars are a bit off topic, but check out the angles of the control arms and notice the placement of them on the body.

http://www.factoryfive.com/hotrodhome.html <and click the photo gallery, you will see the bare rolling chassis flip by.

 

LOL, just reading their promo pages.

 

^^^ thats funny right there! ^^^