Need some help with P/S

Working on a 29 Dodge 4 passenger coupe that has been set up with Mustang II suspension with power rack, it has a Chevy 350. The problem is when I start the eng the steering thrashes back and forth on its own.I have replaced the p/s pressure valve with one that is suited for the mustang rack (supposedly) to create less pressure. Any other Ideas other than being Demon Possessed Thanks Guys... Bob
I also checked to make sure it is not hooked up backwards.

 

I know you said the lines were hooked up correctly, but that is usually what causes this. Or the hard lines on the rack itself are backwards.

 

Sounds like the rack has an internal problem.

 

THE HARD LINES ON THE RACK WHERE HOOKED UP BACKWARDS! THANKS MAN

 

I always enjoy reading these. Never too old to learn something, if I can just remember it at this stage of the game. Tom S. in Tn.

 

I had the same thing happen. Had to ask the same question.

 

Sounds like you solved your problem, but when you open up a system for new hoses/pump/rack; it is good to turn the wheel back and forth numerous times with engine off to help purge air out of the system. Sometimes the air can cause the rack to slam to one side. Purging first will minimize this problem.

 

You are absolutely correct, and I did purge the system this time. I was surprised at how much air was trapped in the system.