I talked to one of our experts at work a while back, he sayd one of the best designs is a type of a ball valve with a V opening in the ball instead of a round hole. Thats how he described it, l havent seen it in person. But for a DIY way l think a gate valve is your best bet.
Some update. I had a problem with the filter sack lately, the support cage in the sack collapsed and it shut off more thain half the sack, engine strugled to draw trugh it. I fixed it and cleaned the entire system, then went to work. Fast startup, but then the system run WAY too rich. I thod the reason is the automixer opened 100% and since the system is fresh and breathable, the opening in the valve is too small. But no, the plunger valve was allmost closed! What is going on???
Anyway, l had to drive on manual.