When strapped in the driver’s seat and the engine is lit, there are three things you can do. You can accelerate. You can stop. And you can steer. While the first two options receive all of the high-performance headlines, many consider tuning your steering for the best feel and performance a black art. That fact is especially true when dealing with a power assist system, which many enthusiasts believe to be totally non-adjustable. That opinion has never been more incorrect.
To learn more about power steering we enlisted the help of Allan Padelford (pronounced Pa-del-ford), the owner of Lee Power Steering in its new home in Valencia, California. For some, the name Lee Power Steering will be quite familiar for its dedication to highly advanced performance steering products. As we were to learn, if you deal with high-performance GM muscle cars that use the classic Saginaw steering boxes from 1965-’92, there is a huge amount of tuning that can be accomplished with these recirculating ball-type steering boxes and their pump systems. If you plan on using the stock frame clip on your project, keeping the stock steering gear system but upgrading the ratio, and especially the valve weight, will give you the feel of a rack-and-pinion system without the inherent bumpsteer, pan clearance, and mounting issues.
To learn about the potential to improve our steering, we rolled Jeff Smith’s 1967 Chevy 300 Deluxe (sister model to the more familiar Chevelle and Malibu models) up to Lee’s for an assessment of condition and ultimately a testing with a wide assortment of steering boxes with different ratios and valve weights.
What is Recirculating Ball-Type Steering?
When GM first offered up their recirculating ball steering it was an efficient and reliable way to deliver a “consistent” steering operation for these classics. While today, the change to rack-and-pinion steering may be all the rage, there is a lot of flexibility with these classic steering boxes as long as you keep the internal mechanisms clean and filter the fluid to avoid having the steering fail, or at least work in a less-than-optimum manner.
It may be surprising to note that in a steering box of this type, there is a gear inside the box called a rack-and-pinion. Its only function is to convert liner motion from the piston to rotational motion of the Pitman arm, which then moves the steering back and forth. However, it is not how the ratio of the box is determined. It is the pitch of the ball screw that creates the ratio. Very much like a course- or fine-thread bolt, it takes more turns to travel a fine thread nut down the bolt than a course nut (i.e., the courser the pitch, the faster the ratio).
Internally, the input shaft is first connected to a valve, (servo valve as it’s known in the hydraulic world), which serves two functions. First, it directs the flow to the piston in the proper direction based on the input from the steering wheel. This is a crucial part of the rebuild process that is called balancing the valve. At Lee’s, this tolerance is checked twice during the process. First, at the valve setup station and the second time during final testing of the steering gear. An unbalanced valve can cause a steering pull right or left as if the alignment is off.
Second, it regulates the amount of assist effort that is put on the piston. Integrated within the valve is a torsion bar, and the diameter of the torsion bar dictates the feel of the steering, or the amount of effort it takes to turn the steering wheel. This could also be described as the balance between power and manual steering.
Some companies refer to this steering valve feel, or effort, in torsion bar diameter. Although it’s true that a larger diameter bar creates more effort in the feel, Lee Power Steering calculates this effort as a function of torque. The amount of torque, in inch-pounds, it takes to activate the power assist. An additional note: changing the pressure at the pump can alter small amounts of effort and sensitivity, but the biggest change comes from the features in the steering box valve.
“The tolerances within a power steering box of this type are far more susceptible to dirt than your engine or even your automatic transmission,” noted Padelford. “The steering valve and the small recirculating balls that move about the channels in the ball screw can cease to function properly if any debris prohibits free movement of the balls or the valve sleeve. In addition, the power steering pump has its own tight tolerance to deal with. The clearance of the piston that regulates the pressure is 0.0002-0.0005-inch. That’s half the width of an average human hair.”
“Like anything that wears, your pump, box, and even the lines require cleaning and changing out over time,” says Padelford. “We have customers who only send us the steering box but we tell them to send the pump as well. While you may think your pump is working properly, if you don’t service the pump at the same time, you run the risk of running dirt and metal shavings through the fresh steering box.”
Padelford continues, that when you drain the fluid out of an old system, the varnish that builds up inside the power steering system that traps small dirt particles can buckle and flake off as the various parts are exposed to air and begin to dry out. As you can imagine, that material then gets dragged into the brand-new box and then back into the pump.
Even when the utmost care is taken, the smallest particle can cause the pump piston to stick in its bore, which will result in a loss of pressure. When changing out a system, even if you are just looking to swap for a different ratio box, you need to supply the pump for cleaning and maintenance and change out or be very diligent in cleaning the lines. There is no middle ground on this.
With most Saginaw power steering boxes, the input shaft is connected to the steering column through a rag joint that allows for some flex in the connection between the two shafts. The “on center” position is critical during installation, something that very few people fully understand from our small sample survey of enthusiasts. What this means is that the steering gear is simply installed in the mid-point of the steering gear to allow the same amount of steering input in both directions. Most importantly, however, is the fact that this midpoint also has a tighter tolerance between the piston rack gear and sector shaft pinion. This eliminates any play when driving in a straight line. This is different from simply aligning the steering wheel during setup.
The Lee Power Steering boxes are marked with a yellow line to denote the on-center point (where the rag joint in the steering column is connected) and another line that denotes the center point of the output shaft, which connects to the steering arm. It should be noted that the on-center point and the steering shaft can be perfectly aligned and the steering wheel still be off-center. In most cases, on-center also means the flat is facing up and the rag joint bolt is perfectly vertical. The correct alignment procedure should be to set the steering box at high center first then adjust the steering wheel and suspension alignment second. Most shops know this, but it’s always good to ask.
One more point of note: a steering box has no ability to return to center when coming out of a corner. That is a task for the frontend alignment where caster and kingpin angle cause the steering to return to center. Many early muscle cars came from the factory with very little caster and when you put a rack-and-pinion system in your ride you are actually taking away caster.
There are several aftermarket suppliers that sell upper A-arms that increase caster angle. Also, if someone has tried to take slop out of an old box by tightening the Allen stud on the top plate on the box, this can make the lash too tight and will create drag and hamper the return to center.
What’s in Play?
With regards to the tunability of a power steering box, there are two main factors involved. First is the ratio of the steering. In other words, that ratio shows the differential in full rotational turns of the steering column/wheel (360 degrees) in ratio to degrees of angle change at the tire/wheel. For example, if one complete turn of the steering wheel, 360 degrees, results in the wheels turning at an angle of 24 degrees from straight ahead, then the ratio is then calculated as 360:24 = 15:1.
Secondly, with power steering units of this type, it is fluid pressure assist that helps the power steering complete its job—or work, as engineers would be prone to stating. For our testing, the steering box in the Chevy 300 was a 12.7:1 ratio box and used a 25–in-lb pressure valve. However, this is not the original box but rather a typical wrecking yard box commonly used in these cars by performance fans.
There is a large range of tuning in the valve weight area of a steering box. Inch-pound ratings can be found as low as 5-10 for handicap vehicles (where high assist is warranted) and as high as 60-80 for dirt and sprint race cars. Lee’s recommends 35– to 40–in-lb valve setting for performance street applications. We learned this very quickly during our testing.
It was clear from the initial testing that the original Chevelle box (with 12.7:1 steering and a 25–in-lb pressure valve) felt loose and was clearly typical of the boxes found in most muscle cars of this era. Adding to the play (loose steering wheel conditions) in the steering feedback through the wheel was the fact that the system was not installed correctly, the on-center position of the steering wheel and alignment was not lined up with the high-center of the steering box. For that reason, the box was not operating to its maximum efficiency.
Our Power Steering Box Comparison
Our test compared four different Saginaw boxes in all:
|Steering Box Test|
|12.7:1||25-pound valve||Original box with worn parts|
|12.7:1||35-pound valve||High performance – street and autocross|
|16:1 variable||35-pound valve||16:1 on-center increasing to 13:1 in each direction – good street box|
|9:1||35-pound valve||Very quick steering – highest price due to custom parts. (It should be noted that this box is not used on most street applications since it uses internals that move away from the recirculating ball system, replaced with a precision acme lead screw that generates higher friction and greater wear.)|
Our testing was completed at Willow Springs Raceway in Rosamond, California. With over seven tracks available at this facility for different types of testing, we selected a course called the Balcony that is most often used for drifting due to its large, flat asphalt surface. To compare the different steering box types, we set up a straight-line slalom section with seven cones, evenly spaced and a large sweeper corner to allow use to see how it performed on a larger radius turn. In addition, we took the car on the highway to note on-center steering control and whether it was easy to control in straight-line driving.
To prepare for the on-track test, we removed the full power steering system from the car the day before and cleaned the box and replaced the original pump with a new Lee Power Steering pump. The new pump had an output of 1,450 psi, which is perfect for street-driven Saginaw steering boxes. For racing applications, pumps with different outputs are offered. We also replaced the lines (2,600-psi high-pressure side lines and 250-psi return lines) and included a Lee’s filter that would keep our fluids clean. With a removable internal element that will remove debris down to 10 microns, we were assured that the system would retain its integrity long term.
We made a point not to repair the original box so that it would be indicative of many boxes currently in use on these types of cars. We simply cleaned it so it would perform as well as could be expected for a worn unit—tightening the steering box arm-retaining nut that was finger tight. Yep, this Chevy was about to lose total steering control.
It should be noted that our test was not a timed test, but rather a purely subjective analysis of each steering box by Jeff Smith, the owner of the 1967 300 Deluxe. Jeff is not only a longtime car enthusiast and former service station tech (a long time ago), he’s a former editor of Car Craft and Hot Rod magazines and was tech editor for a long list of magazines and currently submits tech pieces for this magazine. With 40+ years of automotive experience, he was a great choice for analyzing and speaking eloquently about the differences in each steering box.
The following are the comments we heard from each of the four steering boxes we tested. Original box with 12.7:1 and 25–in-lb. pressure valve:
The system felt very loose overall. The wheel required a crossing over of hands to be able to navigate the cone section. There was play in the wheel when at rest and the assist was over-modulated and vague. Lee Power Steering 12.7:1 box with a 35–in-lb pressure valve:
While the ratio seemed quite similar, requiring the same manipulation of the wheel to make the sharpest corner, the overall feel was like night and day. By virtue of the increased feel, the car just felt like it was much more under control and delivered higher confidence in the car’s handling. On-center feel was good but required more driver attention.
Lee Power Steering 16:1 variable (13:1 ratio at corners) box with 35–in-lb pressure valve:
Overall, it was surprisingly similar to the 12.7:1 system with the 35-lb valve due to the 13:1 ratio steering at the ends of the steering wheel sweep. Slightly more rushed input off center due to the 16:1 ratio but nearly the same crossover on the hands. On-center feel was more relaxing due to the slower steering ratio in the middle of the steering input range.
Lee Power Steering 9:1 box with 35–in-lb pressure value (fully custom box):
Overall feel was dramatically different and when compared to the 12.7:1 box, wheel rotation was cut in half with the 9:1 box. Whereas the 12.7:1 box required crossing over of the hands, the 9:1 box was a quick quarter turn to negotiate the line of cones. The on-center feel—running down the highway—required considerably more input and attention, as you might suspect with a high ratio box such as this. The 35–in-lb pressure valve delivered the same positive feedback through the wheel.
We learned a few things as noted here:
In the end, it was clear that the 35–in-lb pressure valve made a huge difference in the feel and feedback when driving. That alone is something that we found most performance enthusiasts were clueless about. Make certain that the steering system is operating correctly, which means a rebuild at the very least and perhaps a completely new system for most. Understanding the tolerances found in these systems—Padelford noted that the tolerance between the housing and the piston is about the thickness of a human hair—and any system with five or more years of service is probably in need of a rebuild. Also, that $99 core replacement steering box at the corner auto parts store is probably not going to make you happy.
There is a huge amount of tunability to be found within a power steering system. With a number of ratios available ranging from daily driver and competition-level steering systems, you don’t have to stick with one size fit all power steering science.
Our testing revealed the wide variety of power steering options available for owners running the classic Saginaw power steering box and pump. Through the use of optional gearing ratios and valves to adjust the internal leverage point, we changed the speed with which the wheel turned as well as the feedback delivered to the driver. With the additional support items included in our Lee Power Steering system, we created a system that was bulletproof and would deliver years of service. CHP
Photography by Cam Benty