[Fot] Type A OD pressure test

[Jack Wheeler]

Hi Greg.  Here is a tip for you.  When I used to rebuild A-Type overdrives, I would "lap in" the surface that the ball sits on.  I had a spare ball of the correct size, and I welded a small rod to it (about 3/16" diam.).  Then I put a bit of valve grinding compound on the ball, inserted it down into the hole, then turned it back and forth, thus lapping the surface that the ball sits on.  This is a tip that Hardy Prentice gave me years ago, when we were both racing, and obviously the purpose was to minimize any leakage past the ball.  This may be to late in your case, as you would have to do this while the unit is apart, so that you can carefully clean all of the grinding compoound out of the housing after the lapping.  Maybe this will help you next time.  Good luck.

Jack Wheeler
 

    On Monday, March 5, 2018, 12:12:29 AM EST, Greg Blake via Fot <fot at autox.team.net> wrote:  
 
 All knowing FOT

Attached is a video of my Type A OD unit ready to bolt up to the transmission. I decided to do a pressure test with 120psi of compressed air plumbed into the operating vale port. 

The engagement seems to work well when I move the operating lever. But I am concerned about the amount of air that can be heard leaking. I believe it is going past the relief valve. Is this abnormal amount of leaking?

I noticed upon tear down that the nonreturn valve had a 1/4" ball instead of the 5/16" this unit should have had. The test you see in the video is with a new 5/16" ball. I am sure on a previous rebuild someone mistakenly used the later style 1/4". 

Just wanted opinions before I buttoned this up to the transmission for some bench testing. 

Thanks. 

Greg

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