my one buddy has a 58 impala [and yes, i blame any and ALL his problems on his make of choice ! ] with a somewhat odd steering feel, if you will, at center, going down the road.
it is always tight, and if you make a slight correction, as is necessary, it seems to want to keep making that correction, thereby forcing you to correct in the opposite direction.
in other words, you are always "driving" the car, which gets very tiresome quickly.
this car has a new 500 series power box [3 1/2 turns lock to lock], along with ball joints, tierod ends, idler arm and ALL bushings, front and rear.
there is absolutely no slop anywhere.
it has 6 degrees of caster [average], negative camber, and 1/8" toe in.
we have loosened up the adjuster on the top of the box three turns, but saw no difference.
this phenomenon is apparent at all speeds, on most road surfaces, and since the box is lots quicker than the manual box it replaced, gets pretty "interesting" at interstate speeds.
there are new tires on it, but this was present with the old ones as well.
we are leaning toward suspecting the box having a problem, but are baffled as well, as this is not our first time converting early GM vehicles to power steering.
what are we missing here ?
the alignment sheet is attached.
Thanks in advance guys ! our OLD eyeballs and brains are getting worse by the day it seems.

So mopars have an issue where the assist valve can be off and cause it to power the steering on its own.
I don't know anything about this box, but you might put the front end in the air and see if it is self assisting.
might just be barely balanced and force it to lock on its own.
vs being an aligment issue.
I mean it could be, but is a simple check.

Why so much negative camber?

My old 58 had a control valve off the pitman arm. Does this have it or is it some sort of retro fit kit?

i was wondering that myself. the upper and lower arms are heavy duty tube replacements, and the measurements [other than the toe] are what the arms had without any shims.
when we were under at the alignment rack, i think it was mentioned that the way the arms mount, you could not insert shims to bring just the camber back.
i think if some of the caster was taken out, the camber would return to a better position. i'll have to dive under again to see how the upper arms are mounted.

the factory specs according to chiltons [the first book i grabbed, and did no searching on line] are : caster - 1/2n to 1/2p, camber - 0 to 1p, and toe - 1/16 to 3/16

another thing i don't know is what spindles were used. this thing has discs on the front, but i don't know if the conversion utilized the stock 58 spindles, or another year spindle was used.

good point about jacking the front off the ground and seeing if the box wants to "self steer". that is something we haven't done.
another item is the pump used. i don't remember what that is off of, so i'll have to find that out. it may be an issue or not, output pressure wise.

keep the ideas coming guys. very much appreciated !

this is a retro fit box. the car was a manual steer before.
i know the old system you are referring to.
that entire system was used from a 63 chevy with the original straight axle and parallel leaf springs on his 32 chevy coupe. that car was built way back in 69 or so, and was the car that introduced him to me back in 1970. it's been down hill from there, he tries to teach me things from brand X i don't wanna know !

I too question the camber, but I see nothing to indicate the problem he's having. That much caster should make the steering virtually self centering. I suspect the box despite the adjustment attempts.

To me I would have it aligned to 3 positive caster, 1/2 positive camber and 1/16 on the toe. If that does not help the gear box may be the issue.

we are going to take out some caster and see where the camber falls, then see how it acts.
i'm afraid the box is bad, or too fast of a ratio for this type of suspension on an "X" frame, which is known to be very flexy in operation.

my wife ended up in the hospital, so this is on a temporary hold for now.
she is ok and doing good, but will be in for a couple more days.

i did find out the pump with a remote reservoir used was from a pontiac something or other.
i wonder what the pressure is, and if maybe it's too much for the box ?