I have adjusted hundreds of these over the years, but I have always used the special tools and dial indicator to adjust the valves. The 2 return valves get adjusted to about .021" clearance and the pressure valves about .060". You need to have some method of holding the valve you are adjusting firmly on it's seat while adjusting. A tech manual would be a must here, trying to explain the correct procedure without photos is near impossible. I'm not saying adjusting without special tools is impossible, but I have never done it. I always had access to the proper tools. How were the valve seats on the valves and in the housing? Most times the seats in housing need regrinding to get a good seat and the valves have Teflon seats that get dirt embedded in them requiring replacement of valves for proper operation.