Here is a link to a thread on adjusting the steering box for a 510. http://www.the510realm.com/viewtopic.ph ... ent#p99775
This is the meat of the thread:
Roll the car forward a few feet, to make sure the wheels are pointing forward.
Then, take a wrench and loosen the jam nut on the top of the steering box, AT THE SAME TIME, put a slotted screw driver into the slot in the top of the screw, AND HOLD IT IN THAT POSITION! Now, carefully screw the screw down in the box, till you feel some resistance. ( you may have to back the nut off a hair more, to keep it from tightening up) Then, go grab the steering wheel and wiggle it back and forth, WHILE WATCHING THE WHEELS. You want to see the wheels move, with the steering wheel movement. IF not, tighten a bit more. When it seems ok, hold the screw in that EXACT position, and then you tighten the jam nut!
Now, this is whre you find out if your worm and sector gears are bagged beyond adjustment. You have to drive the car, to see if it wants to return to center, AFTER you try to turn a corner. IF it is sluggish, or just plain TOO TIGHT, you have to back OFF the adjustment, till it turns ok, but, if you loose the on-center tightness...YOUR BOX is dead. You will either have to live with that vague steering, try and find a better box, or, try to find a good HL510 box and put that on.
So try a few points , test drive.....GOOD LUCK!
While you can turn the wheels statically, I do recommend you actually drive the car to really see how it's working, and BE CAREFUL when you first turn, as you may be surprised at how tight the box can become, past the on-center feel.
I've recommended too, that the stock oil needs to be cleaned out, and a gear oil put in, with some Moly-G. If the box has survived, you want to keep it in good shape, and give it the better lubrication.
Be very careful, when you test drive...as the steering could be sooooo...tight, that you might have to reef on it to get it to come back. A PERFECT box, is one that has virtually NO on-center slop, turns well, and, depending on castor, should come back to center by itself, if you let go of the wheel.