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Steering Progress

Omni rack mock up

Omni rack mock up

Steering Rack Install
My dry sump configuration meant I needed to come up with a solution that would let me keep my power steering (don’t ask) and wouldn’t interfere with the oil pump drive hanging off the front of the motor. After trying a few different ideas, I settled on using an Omni rear steer rack as it gave me the best options for keeping the same steering geometry as the original car (more or less). After the rack was positioned, I mocked up a cross member in wood. The new rack member will bolt through the frame rails.

Here’s the link I used (thanks Pat McMahon) to determine my rack position and possible bump steer implications: http://www.circletrack.com/chassistech/ctrp_1001_bump_steer_explained/viewall.html

Wooden buck

Wooden buck

The Omni rack body is nearly identical in width to the MGB rack but the track width is considerably different. To get things going, I positioned the new rack on jack stands at the same height and distance from the wheel center line as the original except it was behind the wheel axis not ahead of it. Using the wooden mock up I created for the new steering cross member, I cut pieces of 2 ” x 3″, 16 gauge box beam to the appropriate lengths and angles as well as two end plates from some 1/8″ x 3″ stock I had on hand. The x-member is slightly off-set to the right to provide enough clearance for the steering shaft knuckle to clear the frame rail, but I’m not thinking it’s going to make any difference in the steering. My pal Jeremy came over and did the welding honors for me.

Complete steering x-member

Complete steering x-member

I corrected track width by buying a new set of inner tie rods, cutting them to the correct length and then rethreading them (14mm). I used a new set of aftermarket inner rods for this as they don’t have the adjusting knurls as do the OEMs and provided plenty of material to thread. An important note here, if you decide to do this, you’ll need to make sure you find an Omni rack with screw on inner rods instead of press on. Otherwise you’ll need a trip to the machine shop to replace them.

 

Rack + x-member

Rack + x-member

The Results
When everything was done, here’s what I ended up with. The overall rack width from the center of the ball joints on the outer tie-rod ends was 44″ for both racks. The critical length of the pivot for the inners is off by about 1/4″ in total width (an 1/8′ per side) at 9.75″ for the Omni rack—so not likely enough to effect the bump steer other than that inherent to the original rack. The horizontal and vertical planes of the Omni rack are identical to the MG rack—the vertical distance from the center line of the wheels is the same on both racks and the horizontal distance from the center line is also the same.. The only obvious difference is the Omni rack is rear steer (behind the center line of the wheels) and the B rack is front steer.

The last thing to be addressed was to trim the outer tie rod ends down to allow them to screw on far enough in to get the right track width—about an inch for each one (not enough to compromise the end), about the same as the stock tie rod ends. There was more than ample material to work with on the Omni ends.

The rack is secured to the cross member using the cast in mount on the driver’s side and a simple muffler clamp on the passenger side (the u-bolt variety with the scalloped clamp bar). I needed to change routing of the line that goes from boot to boot to accomplish this (just rotated it 180 degrees).

Later today or tomorrow, I’ll be installing the new rack assembly and will take some additional shots and post them up.

Oh yeah, and I’m sorry for the crappy camera phone pics but my spouse took off to visit family for a few days and the camera went with her. I promise to take some better shots and post them at a later time.

 

Modified backing plate

Modified backing plate

New Spindle Mounted Brake Ducts
The brake ducts are another story. I started out with a set of Allstar Performance spindle mounted ducts and though all was well until I installed the sway bar only to find it interfered with duct work and wasn’t going to permit the wheels to turn fully. For no known reason, I kept the original brake backing plates and I’m glad I did because they came in very handy in fabricating a second set of ducts. A little judicious trimming, some 3″ aluminum tube and, voila, new spindle ducts. Fit perfect, no interference, happiness all around.

 

New spindle mounted duct

New spindle mounted duct

New duct

New duct installed

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