Steering won't self-center

[Aracer]

Max. Caster is set by turning the rear offsets in towards the engine till horizontal, they go around and don't stop like the A body's, the fronts the opposite direction, out ward till level.
     Now check the wheel with a digital level, by setting on various areas of the wheel or dust cap on mags, the camber needs to be in at the top towards the engine and will read 89.8*, for the E- body handling with wide tires.
       So you get this by FIRST adjusting (loosen the 3/4" nut) the rear upper control arm cam (offsets) outward until you get the camber back to (in towards the engine, at the top of tire) 89.6-8*. This gives the max. possible  caster, aprox 3.5*.
      In some cases on the pass. side, the front cam will end up slightly in, on the down side, and in on the up side direction on the drivers side (because my car is higher in the back than stock), this may happen when the cars drivers side is lightened by removing a power steering gear and power brake booster for aluminum m. cyl., or else the drivers height adj. screw may have to be set in  the lower control arm much deeper than the pass.. My E body rear adj. cams are all the way in towards the engine.   
      My car's rear cam offset, did not need a second adj. , only the front cams did, to remove an excessive, "out at the top of tire" camber setting.
     The car has to sit level and all parts , left to right have to be mirrored in height to floor, for example the idler arm, to gear arm attachment and the center link level. Check on bigblockdart.com for Riely's advice.

[Cuda Gooding]

I think the caster is not like on a shopping trolley, it's the other way round, like on a motorcycle.

The caster on the front wheel of a shopping cart is basically the same as the caster on the front wheel of a motorcycle.  If you project a line through the steer tube (or the pivot on a shopping cart caster) it will hit the ground in front of where the wheel contacts the ground.  The further forward that imaginary point is relative to the tire contact patch, the more caster you have and the more return to center effect you will have.

Lifting the rear end of the car will shorten the distance from that imaginary point to the wheel contact patch.

[Aracer]

Lifting the rear end of the car will shorten the distance from that imaginary point to the wheel contact patch.
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The caster goes away when you jack up the rear, so you have to add more; you will also get more toe in from the rear rise, so you have to remove some. that's why the old straight axle pick ups handled worse when loaded to the gills; due to less toe in,  they wander left and right. Too much toe in and they wear out the fronts when unloaded.

[Skunkworks Challenger]

Lifting the rear end of the car will shorten the distance from that imaginary point to the wheel contact patch.

The caster goes away when you jack up the rear, so you have to add more, you also add more toe in. that's why the old straight axle pick ups handled worse when loaded to the gills; due to less toe in,  they wander left and right. Too much toe in and they wear out the fronts when unloaded.

I'm happy to see somebody finally explained what I was saying about caster being affected by lifting the rear for rake.  PK