[RLM61]

imported post

first off thanks for help on bench sync carbs as they were definitly out of adj.my question is,what does air cut off valves do and how do they work. also working on vacum gauges and was wondering, ive seen damper valves placed on intake and on gauge side. was wondering which side should they b on.:waiting: also, would it pay to search welding shops for 5mm nipples or just order from dealer. thanks RLM61

 

[DaveO430]

imported post

The air cut offs block an air passage to the low speed jets until high vacuum( deceleration) opens the passage and allows air to enter above the jet and effectively shut the fuel off to prevent backfiring.
Don't quite get what you mean by the damper valves but I assume you mean valves to reduce the flow to stabelize the gauges. I don't think it matters much where in the line they are placed.
For the nipples get a length of 3/16 or 5mm steel brake line cut in pieces 2 or 3 inches long and thread one end 5x.8 mm.

 

[RLM61]

imported post

thanks,info helps alot. so if engine does not backfire upon deceleration,air cut off valves are working properly. also will be using brake line for fittings. do you seal threads with teflon tape or use small washer and oring. i am also going to calibrate all gauges to #3 carb as to get accurate readings on gauges before carb sync because ive heard even though same gauges. may not be calibrated the same. RLM61 THANKS

 

[DaveO430]

imported post

The air cut off diaphragms can go bad and cause a vacuum leak but it would not necessarily cause a backfire.
Some type of seal on the adapters is good, either teflon tape or a nut and o-ring.
Good idea on calibrating the gauges.