Anybody,

First off, I have an adjustable external wastegate. There was a set screw on top, directly in the center to adjust the boost setting. It was held in place by a nut.
Well, I just got my t70 project together, and I go for a test drive. At first the wastegate is set at like 9lbs and is working properly. Then I idle it home, and do a couple of things and go for another test drive. This time boost is uncontrollable. I was seeing 18lbs at 3800 before I would let off. SO I go home and jack up the car to diagnose and to my surprise the set screw is completely gone.
Now here is my question, I know the thread pitch and diameter of the set screw, but I have no Idea how this thing works internally. Does anyone know what I should do??? with the set screw gone, could anything have messed up internally with the wastegate??? Also, anybody know the length of the setscrew? Could something have fallen out?
I got the wastegate from ebay, it is the "HKS Style wastegate"
Any help would be appreciated.

 

The screw is a spring tensioner. It allows you to run higher boost levels by cranking up the "preload" on the wastegate valve. With it gone the wastegate should be opening at the usual 9 lbs. I've picked up a similar wastegate and have yet to try it out, but I fear this may be a case of "we got what we paid for". In this case, a cheap knock off part that seizes up when you get it a little hot from a rotary. My advise, pull the wastegate off and bench test it. Mine cracked open at 25 psi (diaphram port pressure only) which should be about right for 8 pounds of boost if you take into account the pressure the exhaust is exerting against the valve. Give the wastegate 10 lbs of air pressure and try to push open the valve. add a bit more pressure and try again. I would advise staying under 30 psi so you don't rupture the diaphram.

I think I'm still going to test out my cheapo wastegate, but I'm putting a 10 psi pop off valve on the car just in case. If I hear the pop off when I'm under boost the HKS knock-off is going in the trash.

hope this helps.

-Trent