'67 Dart drag car with a rack and pinion swap needs some geometry help

-

wahzinaplymouth

Well-Known Member
Joined
Jan 24, 2006
Messages
103
Reaction score
15
Location
SLC Utah
I have a '67 Dart that is drag only that has been swapped to a rack by a previous owner. It has the '73-'76 disc set up with the lower ball joints swapped side to side so tie rod attaches in front of the wheels. The rack is connected to the LBJs via a factory tie-rod end. Knowing that there are really only 2 ways to fix this(back to stock steering or a full K frame/steering swap), I am really wanting to make the thing turn halfway decent until I can save up the coin to do a k frame swap. The angle of the front wheels with the wheel turned to the right will cause the tire to rub the top of the fender on the drivers side unless I set the torsion bars up higher than preferred. Turning radius leaves a bit to be desired as well. The car drives arrow straight and since it is a drag car, I'm not looking to mess that up or for anything crazy in the turning world, I would just like to improve it's functionality some for those back and forth through the pits and staging lanes. The down the road plan is to either front half the car or a k frame conversion but can't afford the cost at the moment, so lower cost improvements is the direction at the moment.
What I am hoping to find out is if anyone here has had experience using heim joints in place of the tie rod end and a spacer to lower the angle of the rack arm coming into the ball joint as this is something others have recommended. But I haven't seen pics or first hand evidence of this. So, are there are kits or am I making my own kit? Does anyone have parts and part number recommendations for this and can I truly expect any improvement by doing this?

Thanks in advance for any info!
 
Last edited:
That is what I thought, the problem is by swapping the steering link from the rear (correct geometry) to the front make it way off. The simplest way to explain it is for you to take an imaginary line from the center of the rear end to the front ball joints. Your tie rod needs to intersect that line, be it in front of rear of the ball joint. As you have experienced, your steering must be a nightmare making turns.
 
91636055_R_fcc19ed4-5d6e-4d25-a23a-cf43220631de.jpg
The biggest issue with this is it is setup for a 5/8" rod end.
You would need to find a GM (80 malibu) inner tie rod (LH thread) and the correct length swedge tube .. Look in speedway motors oval track section.
 
That only helps bump steer. Not steering geometry.

OP states two problems: steering geometry and large angle of the tie-rod to the BJ. @mod5v shows the fix for the large angle, assuming that's the angle OP references.

The swapped BJ's will give a poor ackerman angle, but that doesn't matter much for a car used mostly in straight lines. Ackerman really only helps in a zero-scrub situation anyway (parking speeds). Cars at high speed benefit from anti-ackerman or something in between depending on tire and actual cornering speed. If his car is already good at going straight, no reason to futz with it. Fixing it might help turn a little tighter at pit speeds, but it's not going to cut the turn radius in half.

Fixing the turn radius with a rack means shortening the steering arms to increase wheel angle. A custom lower BJ housing would be perfect for this, but I'm not sure they exist for dodges. Wouldn't be hard for a decent shop to fab though. Welded 1/4 or 3/8" plate with a threaded ball joint would likely do the trick, and then the height of the steering arm can be placed wherever to fix the tie-rod angle too.

Swapping the whole front end to make a drag car turn better and reduce a rub seems like a lot of money to spend versus wheels with more backspacing and rolling the front fender lips... but that's just me. I'd go with a slightly smaller tire and jack the front end up to get the same fender height and enjoy the increased clearance.
 
View attachment 1715437295The biggest issue with this is it is setup for a 5/8" rod end.
You would need to find a GM (80 malibu) inner tie rod (LH thread) and the correct length swedge tube .. Look in speedway motors oval track section.

Something like this gets sketchy as the placement of the rod end moves away from the steering arm. Adding a second plate to put the stud in double-shear would be a good idea.

See the diagram below. The 'race bump-steer kit' shows an added flange to the lower right of the tie-rod. This helps support the stud that the tie-rod is pulling on so that it doesn't twist and eventually break.
911-strut-service-diagram.jpg
 
Thanks for the input everyone. Helpful points made by all. Turning is definitely a nightmare but I only hate it at very slow speeds and from a stop or in tight quarters.
For me, the front end swap would have more benefit than just improved turning and geometry - weight reduction, improved header clearance, additional tune-ability of the front end, getting the ride height where I want it... I want to lighten the car up some and make things easier to adjust and work on so eventually this upgrade will happen.
This rack setup was a concern when I bought the car, but I wasn't too worried about it, being a drag car. If it was a street car, I'd put it back to factory. I'll investigate some wheel options for now. Thinking this might be the best option right now to buy me a little clearance. Being that it does go beautifully straight and seeing some of the responses here, it will probably remain as it is for now.
 
The double shear is always better but some times not practical. That said there are a lot of dirt track race cars out there that use the bump steer spacers. Dirt tracks are not known to be the smoothest surface to race on. I have been on tracks that resemble a freshly plowed corn field and the stock spindles with the spacers do hold up surprisingly well.
 
Thanks for the input everyone. Helpful points made by all. Turning is definitely a nightmare but I only hate it at very slow speeds and from a stop or in tight quarters.
For me, the front end swap would have more benefit than just improved turning and geometry - weight reduction, improved header clearance, additional tune-ability of the front end, getting the ride height where I want it... I want to lighten the car up some and make things easier to adjust and work on so eventually this upgrade will happen.
This rack setup was a concern when I bought the car, but I wasn't too worried about it, being a drag car. If it was a street car, I'd put it back to factory. I'll investigate some wheel options for now. Thinking this might be the best option right now to buy me a little clearance. Being that it does go beautifully straight and seeing some of the responses here, it will probably remain as it is for now.


One thing you can do to get some relief is raise the front end a little bit which will make your tie rods closer to parallel to the ground. Another aspect I forgot to mention is the tie rods pivoting at the same point as the lower control arm so they move together.
 
unfortunately, the cheapest way to make it safe to drive is put it back to stock.

Your steering / ackerman issues are caused by the builder swapping the LBJ / steering arms side to side to attempt to mimic front steer spindles. To fix this, I would recommend using front steer spindles (Mustang II) but they are not compatible with a factory (style) K.

ackerman 101.... the inside wheel turns at a tighter radius than the outside wheel and is built into your factory steering arms. When the steering arms are swapped side for side, the outside wheel NOW turns at a tighter radius than the inside causing the outside tire to scrub or try to rollover the rim....not good.


The rack and pinion placement...... up / down / forward / back in the chassis is CRITICAL. Without proper placement, expect serious bump steer issues (car dancing around) whenever there is any suspension travel. The higher the speed....the bigger the dance. This CANNOT be "fixed" by moving the outer tie rod up or down unless the rack re: inner tie rod pivots are mounted in the correct place in the first place. Otherwise it is a dog chasing his tail.

Just trying to help with explanation, MHO....others may vary.
 
Last edited:
As I read your issues they have nothing to do with the steering changes. Ackerman issues do not cause the tire to rub the fender, they cause a tire to drag on the ground at full turn. Skinnier tires, shorter tires, or different offset wheels will fix that issue. The late discs do move the wheels/tires out farther.
 
After seeing & reading this post, I would be concerned of the stress being put on the steering components being a race car only. It's probably just a matter of time before the car is launched, comes back down, & something fails. (i.e. tie rod end, ball joint, idler arm, pitman arm). If it were me, I'd garage it until I could afford to make it right. Is the thrill of racing worth risking you or someone elses life over?
 
Pic #5 is a good depiction of a bump steer correction, but your problem is probably more in the ackerman. Front steer cars have outer tie rod ends that are outside of the steering axis, whereas rear steer cars have the outer tie rod inside the steering axis. The closer the angle between the steering arm and the tie rod end to 90 degrees, the less the tire will turn. When you turn the steering wheel, the angle changes; one side goes towards 90 degrees; the other side away from 90 degrees. You always want the inside of the turn tire to turn more than the outside. I'm iso a cheap rack for my 66 Dart and my 62 Dart. I bought 95 mustang spindles and rack...but still configuring..
 
Last edited:
-
Back
Top