Swapping to rack and pinion steering

Many cars suffer from poor turning radius after an R&P install.  There are 2 basic reasons.  Either the rack was placed too far left and interferes with the wheel, or no adjustment was made to the steering arms.  On a typical RB type steering box the pitman arm has a “throw” of 7 inches, side to side.  It is usually connected to steering arms effectively measuring 7 inches long.  (The 7 inches is measured from the center of the steering arm mount, where the king pin or ball joint pivots the spindle, to the center of the outer tie rod where the steering pivots.)  Typical racks (Cavalier) have 6 inches of throw and originally connected to the upper strut in a manner that represents about 5 ½ inches from center of the strut to the center of the tie rod.  Connecting the rack to the original arms causes a loss of nearly 20% of steering angle.  It is strongly recommended that this be dealt with before installing the rack.  

[[Image:Chevelle_arm_vs_chevy_arm.jpg]] 55/57 chevy arm compared to 65 chevy arm.

Our bump steer (toe in) changes less than ¼ inch at full suspension travel, and less than 1/8 inch in normal operating range.  I’ve been told additional toe in is beneficial during hard acceleration or hard braking, as it tends to stabilize the front end.

If you are going to install a power assist unit, there are still a few more issues.  The power pump for the Cavalier rack is designed to fit a cross mounted front drive 4 or v6, didn’t even try to make it fit my early 80’s SBC.  Just went with an original pump that fit the original brackets.  Piece of cake. The Rack will have a tube and O ring style connector for the high pressure hose (metric).  There are adapters available that convert that to an old fashioned flare fitting, just like the early model pump.  Because the pump and the rack sector end up so close together, you may want custom hoses made.  

Once every thing is hooked up and functioning, you can test drive your creation.  It may not feel just right. A rack is more sensitive than a RB box. Higher caster will help keep it centered. If it is simply to “light” “soft” or “over responsive” you may want to address the flow and pressure differentials between RB and R&P.  Most older GM pumps will have a pressure rating as high as 1350 pounds. 82 – 94 S10’s have the lowest at around 1100.  The Cavalier rack was designed for a pressure of +/- 1,000 PSI.  You can address this with a simple shim kit from Borgeson. The pressure relief valve is located behind the high pressure output fitting on the back of the pump. You may need a small magnet to pull it out of the recess. The shim kit comes with a tool to help with removing the end nut, a new O ring for the outer fitting, and several shims with a guide on how many shims to use to attain certain pressures. Basically, additional shims reduce the pressure on the spring, allowing the bypass to open sooner and recirculate the fluid, rather than force it to the rack.  The kit allows for reduction to about 750 pounds, suitable for a mustang rack, which allows you to get well below the normal range for a Cavalier rack. Reduce the sensitivity to your own liking. In most cases, the pressure reduction valve can be removed and replaced with the pump in the car.  Yes, you have to drain and refill the pump each time, but that’s pretty minor.  The second adjustment available is flow rate. Determined by the size of the hole in the high pressure fitting (the one you took out to get to the pressure relief valve) on the back of the pump.  The earlier pumps had an output hole of 5/32. The cavalier pump has an output hole of 1/8, (Approximately 40% less.)  I could not find a fitting with the smaller orifice to fit the older pump. (Newer GMs are metric fittings.)  Perhaps if you start with a later S10 pump, metric will not be an issue?  As an alternative, it was fairly simple to weld shut the orifice in the original fitting and re-drill it to 1/8th inch. The experts contend; reducing the pressure will reduce the amount of assist provided, which can be reduced below factory specs to give it a more heavy feel. The system is designed to give more assist the further you turn the wheel, (parking for example). You can't harm it by providing less than factory pressue. The flow rate seems to be more of a factor in the sensitivity over center, where you really don't need any assist.  Both changes were noticeable from the original test drive.

[[Image:Orifice_hole.jpg]] weld up and redrill the center hole, not the side hole.