marc9889

I have a ’72 with a big block. In the last 2 months, I’ve replaced the upper and lower control arms with Vansteel units, as well as the springs, which are 550lb Vansteel. It has new Bilstein shocks on the front. It has a new power steering pump, new control valve from CSSB, and new hoses. Ball joints and tie rod ends are also new. Car was put on the ground and upper control arm bushing bolts were tightened as close to torque specifications as possible (it’s not possible to get a torque wrench on all 4 bolts with the car on the ground). The control valve seems to be adjusted properly. I had a 4 wheel alignment done last Saturday. Literally, everything in the front end is new, except for the power steering cylinder, the Pitman arm, and the steering box. In the rear, trailing arms are new, as well as all the bushings that connect links, etc.
Problem: I hit a significant bump, and the car lunges to the left. Afterward, it continuously pulls to the left. A quick jerk of the wheel to the right will “correct” it and eliminate the pull to the left.
Could this be something as simple as a sway bar adjustment?
Will wear in a cylinder allow enough fluid to get by the piston to allow a lunge like that?
On a positive note, not one drop of power steering fluid has hit my garage floor since it was finished. I never thought I’d see it happen…

Big2Bird

A few items to check.

Air in the system will do that.
Control valve not adjusted properly.
Alignment is not correct.

marc9889

After the new control valve and power steering pump were installed, I filled the reservoir with fluid, and turned the wheel left and right, stop to stop about 20 times, then took the car off the jack stands and drove it around for about an hour. Is there a better way to purge air?

Big2Bird

You should do that twice, and then shut it off for 30 minutes to allow air bubbles to dissipate.

You sound okay there.

Jack it up, disconnect the ram, and see what it does while the wheel is straight. There are other threads about adjusting the valve.

If not these, then the alignment is wrong, or he left something loose.

Bloodzone

How much caster are you running?

marc9889

Caster + 2 1/2, or so I was told.

Disconnect the RAM from the bracket that attaches to the frame, correct? (the end where the rod attaches)

Big2Bird

Yes. With the valve in neutral, engine running, the ram should not move on its own, and you can gently push/pull it in and out.

marc9889

I have not tried that, but I'll put it on my list.

Big2Bird

When you align a Vette, you do it while settled. If the guy jacked it up at all when attaching the alignment lasers, he doesn't know how to do it correctly. Seen this before.
I do my own old school with strings, but that's another thread.

marc9889

When he did the alignment, it was planted on all 4 tires and under it's full weight, so I think we are good there.

On the subject of alignment, is a caster adjustment performed by adding/removing shims to the space between the frame and upper control arms?

Big2Bird

Yes. Camber add/remove equal shims. Castor, move shims from front to rear/vice versa.
Toe in, adjust steering rods. You should be slightly toed in. No toe in is darty. Toed out, and it will do as described.

Rear, shims are moved from inside to outside to adjust toe in. Full shim pack when tightened.
It MUST have a slight toe in here. Camber is adjusting the rear struts till vertical. I have a 16" level for this.

Again, anything loose, ball joints, sleeves, shims,nuts, anything loose will do stupid stuff.

marc9889

So in the case of my new trailing arms, a full set of new shims is all that is required to get the ideal toe-in, aside from moving the shims to one side of the trailing arm or the other, correct? I ask because my alignment guy told me that "he didn't have any shims for the trailing arms". When I mentioned that the car already had a full set of new ones, he told me that it was already very close to perfect, but bring it back if it did anything funny. Looks like I'll be measuring it myself...

Big2Bird

Yes. If its toed out at all, you will get bump steer, and it will crawl sideways when accelerating or decelerating. I would shoot for 1/16" both sides for 1/8" total.
Front, maybe 3/16" total.

marc9889

Excellent info, thank you. If you ever have the misfortune of being in Alabama, I insist on buying you a beer or two.

Big2Bird

Your very kind,.

marc9889

You were exactly right. Yesterday afternoon, I unbolted the cylinder rod from the bracket and started the car. Sure enough, the rod slowly started moving to it's fully extended position. I shut the engine off long enough to pop the cover off the end of the control valve and find a tool to turn the adjustment nut. I restarted the car and adjusted the nut so that the rod was neither extending nor retracting, then pushed the rod back in far enough to put it back into the bracket and bolt it back up. The whole process took about 15 minutes.

I also checked my tire pressure and found that each front tire needed about 6 more psi, which I took care of. Afterward, I adjusted my sway bar end links so that the driver and passenger side has as close to the same number of bolt threads exposed as possible.

I took the car out on the same stretch of road that revealed the problem in the first place, and what an amazing difference. No lunge, no steering pull, and a great, smooth ride. Thanks again for the help.