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My car is 1966 Coronet street cruiser that will make an occasional pass down the drag strip. At best it will be a high 14 second car. Vehicle will maintain stock front end ride height. Slightly raised in the rear.
My question is; if I were to use a stock upper control arm, with the taller spindles, what are the potential safety issues? I guess I am not quite understanding what the 3/8 in. of height in the spindle does to the front end geometry to a point it becomes dangerous and under what driving conditions will it become risky? If someone can explain the cause/effect of the mechanical side of things, I can make an sound decision for my application. Spending the $350 isn't a big deal for the FFI tube control arms if this prevents me from hurting myself or someone else. On the other hand, I don't want to spend $350 for UPA's where the stockers will be OK for my application.
Thanks for all of the replies, lots of good info.

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you're fine using your stockers, IMHO (I'm an engineer, too

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Vehicle will maintain stock front end ride height. Slightly raised in the rear.
My question is; if I were to use a stock upper control arm, with the taller spindles, what are the potential safety issues? I guess I am not quite understanding what the 3/8 in. of height in the spindle does to the front end geometry to a point it becomes dangerous and under what driving conditions will it become risky? If someone can explain the cause/effect of the mechanical side of things, I can make an sound decision for my application. Spending the $350 isn't a big deal for the FFI tube control arms if this prevents me from hurting myself or someone else. On the other hand, I don't want to spend $350 for UPA's where the stockers will be OK for my application.
Thanks for all of the replies, lots of good info.

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potential problems
1 Running out of travel on upper ball joint. Especially if you're running stock or undersized (6cyl) T-bars. This is a legend that has been perpetuated by Eberg, et al. I was concerned so I checked travel on my car before using. I found the stock original equipment 30+ year old joints were FINE. However, I'm dealing with an A-body. For your peace of mind check to make sure your UBJ setup doesn't bind thoughout full suspension travel. Best done with T-bars removed. If it does-easily remedied with FFI upper arms.

2 Bumpsteer/toe change-- What torsion bars are you planning to run? With stock T-bars you will see many inches of suspension travel. The bumpsteer or change in toe will be more evident. What does this mean? You may need to make a minor steering correction to keep the car on your intended path. Will it feel worse than a 1966 Coronet did when it left the showroom on bias ply tires, I doubt it...
I'm running 1.20 bars on my car and G-Machine is also running much larger bars. And we're both at much lower than stock ride height. Our suspension travel is greatly reduced compared to stock so for me... bumpsteer has not been an issue. YMMV

my qualifications
BS in engineering
former professional driving instructor
20+ years racing and autocrossing
4 top 10 finishes at SoloII nationals

Remember all the advice over the internet is free, you get what you pay for. Hopefully you have the info you need to make your own decision. I was not encouraging nor discouraging use of alternate spindles, merely explaning what you get when you use them.

Montclaire - you're almost enough to make me go back to GM products

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Everyone seems to have different opinions about this subject. What I'd like to know is: what qualifications does everyone posting here have, so that way we can know the education or experience everyone has when it comes to auto repairs/racing/engineering, etc.?

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-BS engineering Iowa State University
-SAE Mini Formula Design team suspension design and team leader for scratch built race car.
-Autocross 68 Barracuda with A-body disk brake conversion:
-Completed many suspension design seminars and classes
-own extensive suspension design resource library

-Created the first website dedicated to technical aspect of Mopar suspension modifications http://hometown.aol.com/pwall5/cars/2cudapag.html
-One of the founding fathers of the Mopax web group uniting Mopar owners that autocross and road race their cars.
-Draw from and contribute to the knowledge base in the Mopax web group that has some of the top performing Mopar race cars in the country.

-16 years suspension design on stock based suspension then 90% fabricated suspension design
-Suspension design as member of 2005 Nascar track championship team
-Most wins in class during last 3 years
-Race team is prototype “house” car for leading chassis builder
-During and before championship season performed many suspension geometry changes with actual recorded geometry measurements before and after AND complete on track performance analysis and measurements.
-Changed roll centers, camber curves, effective spindle heights, UCA angles, lengths, dive angle…. on and on… And those were the more common changes.
-Trained on various computer suspension design programs like the one Reilly uses.
-Trained and access to $10K shock dyno, computer weight scales, bump steer gauges, tire pyrometers, tire humidity, and other suspension analysis equipment.


I agree with what Autoxr says and has found by experience. Tall spindles ok and not mandatory to have tubular uppers. I have found the same to be true in my testing.

I have seen and witnessed the Moog K772 upper ball joint take a ton of abuse with no failure in sheering and braking. These are the same UBJ used in allmost all the Nascar suspensions. They are used because they are such stout pieces.

I have seen the K772 not fail when:
-the tubular upper control arm was pretzel'd by a 100 mph concrete wall impact
-tubular steer tie rod sleeves were snapped in half
-lower control arms were pretzel'd
-tubular upper control arm to frame shafts were sheared off
-whole suspension was shoved up into the chassis and the ball joint pin was WAY over extended to the degree that the tubular A-arm to ball joint ring was shared off. The rim ended up higher than the fender

I have seen the K772 ball joint pins get bent and the socket not move freely after a hard hit.

I have seen the K772 fail in shear or pulling the socket out on rare occasion with accidents that were so bad that it would not matter if it was still connected. The entire suspensions were smashed into and "stuck" into the chassis in those cases.

All that said, I do understand a magazine and factory engineers not approving this "swap". A swap is for everything equal. This is not everything equal and thus not technically a "swap". IMHO, the tall spindle issue is sooo closely related and "assumed" to a disk brake "swap" people are afraid of the liability issues.

Although a carb change is not a swap either. There was a carb shop that specialized in carter carbs in Missouri that wound not sell you jets unless you sent a letter to them telling your car was not street driven.

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My taller spindles have been on since 1992. Zero problems of any kind. Getting it aligned was no problem ...

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AutoX, I hope you haven't taken any of my opinions on this personally, and I've tried to always show that the main problem I have with this idea is to present it as a 'swap', as you've said.

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Go drive an F, J, or M-body fast on an undulating rural two-lane. Now do the same on a good, stock A, '62-'72 B, or E-body. Anyone who's been there and done that will instantly agree that bump-steer - which the static alignment will never see - is nasty.

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I can't see why anyone would want to risk buiding an ill-handling car. Esp. when properly-forged repros of the right knuckles are readily available.

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BTW, I can't believe this is still being discussed. Jeez!

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This says to me that the problem with bump steer is inherent to the F/J/M suspension design, not (necessarily) the extra height of the spindle. Unless, of course, swapping, er, chagning an F/J/M spindle out for a 73+ A-body spindle corrects the bump steer. If that's the case, this is a detail I have somehow missed until now.

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Where can I get repros of the A-body knuckles? Unless they're crazy expensive, it might be worth just getting those for a future project rather than scrounging up another pair of the correct A's.
Clair

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A "tall-spindle on a so equipped factory car isn't going to give you the same "bumpsteer" affect as putting them on an E-body, A-body or pre-72 B-body. The "points in space" are not the same (geometry is different). IIRC the taller spindle was required to compensate for the body insulator/Isolator/biscuit that arrived in the 73 B-body and F/J/M.

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This says to me that the problem with bump steer is inherent to the F/J/M suspension design, not (necessarily) the extra height of the spindle. Unless, of course, swapping, er, chagning an F/J/M spindle out for a 73+ A-body spindle corrects the bump steer. If that's the case, this is a detail I have somehow missed until now.

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I think Rick was using it as an example of bumpsteer, as those cars were known to have bad bouts of it due to the oddly shaped t-bars. The point is that the taller spindles cause changes in bumpsteer through travel, causing similar habits as those of an F body. Not that the taller spindle is the cause of bumpsteer in an F.

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From the measurement I have seen, the taller spindle is “taller” from the spindle axis to the upper ball joint. Everything else is the same. That shouldn’t effect bump steer.

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