Adjustable upper control arm opinions.

72bluNblu said
There can definitely be some debate about this, because there are of course different philosophies on what makes for better handling. And some of it will be driver preference and the rest of the car set up too.

Absolutely.

72bluNblu said
I'm curious though, since you measured everything, what the difference is between the center to center on the UCA and LCA pivots vs the centers of the upper and lower ball joints with the A body or FMJ body spindles. Does a level LCA (pivot to center of ball joint) actually put the upper ball joint above the UCA pivots?

A-Body:

F-Body:

Note that the inside upper pivot height is dependent on caster and such. Because it is a sloped mount, the effective height is where the UBJ is at 90 degrees to the two mounts. Here is a side view of the F-Body spindle:

So less caster would move the UBJ forward and effectively raise inner upper mount height.

72bluNblu said
Regardless, not everyone runs the LCA parallel to the ground, because that's a pretty low ride height. I don't think Peter runs his that low.

Agreed, and no one should feel like they have to have to run their car that low. Frankly, I can't say for sure that I am that low with my '74. It's more of the ideal in my mind, since it get's the RC as low as possible.

72bluNblu said
In which case, you would need the taller upper ball joint to put that angle on the UCA.

True.

To be clear though, the slope of the UCA needs to be up to the UBJ when the LCA is flat. If the LCA is not flat but instead slopes down to the LBJ, I wouldn't want the UCA sloping up to the UBJ as the RC would actually climb then.

Here are some examples.

A stock A-Body ride height has a static RC of 6.3".

With the F-Body spindle and 1" longer UBJ, the RC is over 10".

This is using the stock alignment specs, don't miss that.

So, in my inexperienced opinion, regardless of ride height, an F-Body Spindle and 1" longer UBJ would be a detriment in all cases (in theory) because the RC would be higher and jacking forces greater.