Leaking Prop valve

[Cautrell05]

Been having issues with leaking proportioning valves on multiple vehicles. One is a 65 Impala with a power disk conversion and the other is a 64 C10 with the same conversion. The Impala has had 3 different valves on it now. So far the third is holding. The 64 Pu came in the shop this morning leaking from the same place. I dont like this pattern. Is there a better source to get them from? The impala kit came from classic industries and the Pu kit came from Classic performance products. All of them have been leaking from the rubber plug on the front end that covers the little metal button. Any ideas here?


Thanks
Nick