Air Screw adjustment

I made a new version of my little Pictorial because of i was unable to post the pdf version here (it was 800kB big)

Pictorial - Air Screw Adjustment

Thanks for the instructions. Very easy to understand.

Thanks for the instructions.i have now problem with this.

Awesome presentation, thanks!

hello
because I can not find any of these instruments and to do a fine job, I'm interested in whether some can be by the number of revolutions of the screw do business

Here is a link to a DIY Manometer that can be used to adjust your air screws. http://www.thecubestudio.com/CrossfireHomeBuiltManometer.htm

Click on all the links in the article first because at least one of them has a good view of how the finished device should look. Based on that view it should be much easier to figure out the preceeding steps.

If it isn't mentioned in the text the finished manometer should be in the vertical position when in use. The longer you make the "U" the less apt you'll be to suck the fluid into the intake system. I used brake fluid in the device I made and my device was 1 meter tall with 1 additional meter of tubing extending on each side to reach the vacuum lines on the intake system.

Also, some of the words in that article is in "colloquial" English so some things may be down right incomprehensible.

Anyway, I hope this helps.

Tim

I made up a system like the two bottle manometer shown in the Utube video. It takes longer for an out of balance system to suck fluid into the throttle body. To make things easier and faster I bought two Harbor Freight vacuum gauges, inserted to plastic acquarium valves in line with each gauge so that I could adjust for minimum needle flutter and used that for a fine gauge type balancer for less than $20 total. Before using the first time I T'd the two gauges together so I could connect them to the same vacuum source to make sure the two gauges registered the same or needed a correction factor. The two gauges I had were the same within less than a 1/2" of mercury which is more than sufficient for balance. Actually once the throttle plates are open more than 25-30% throttle body balance doesn't have much effect on the engine operation. You may hear a metallic knocking sound if the bodies are way out of balance but usually only as you open the throttle and the engine begins to pick up the load. This happens because one cylinder is taking up most of the load which sets up vibrations due to the unbalance. The sound and vibes will go away as the throttle is opened and engine speed rises. You can do a good job balancing four cylinder engines with a two bottle or gauge system as well. One just balances a pair of cylinders at a time then T two cylinders together on each guage and balance the two banks together. A bit slower than using four gauges but works just fine. Having owned a '57 MGA with side draft SU carbs I got pretty good balancing the things. On that car it seemed to need it about once a month to keep it running smooth.

https://www.youtube.com/watch?v=MbiI5CbKoWo

thx you very much i m gona try this.

hello,

does someone have a tutorial or pics of the air screw adjustment?
i can not open the link above.
thanks in advance.

https://www.youtube.com/watch?v=Y_WDF6glD5k&app=desktop

The air screws are accessed under the maintenance cover under the seat. There are two hoses teed together coming off the top of the intake manifolds, remove these and connect the manometer tubes to the nipples. Whichever side has a the higher vacuum, screw the adjuster out counterclockwise until both sides have the same reading. This is to be done with the motor fully warmed, and at 1300 rpm. The idle speed adjuster screw is right in between the air-screws.

thanks for the info. so the vacuum for the 2 cilinders is the same?
because in the manual they say vacuum difference 20mm HG. or do they mean sommething else?
thanks in advance.

Ideally the vacuum should be the same, up to 20mm Hg difference is acceptable.

thanks very much for the info.
greetings.

As background; if you are old enough to remember the pre-FI days of carbs, the synchronization was to set the throttle butterflies so that they flowed the same amount of air at idle (as measured by the intake vacuum). The FI system in the Wing uses fully closed butterflies and starter valves to set idle speed. The starter valves are a controlled bypass for air around the butterfly. Individually the starter valves can be screw adjusted relative to each other so they flow the same air volume. The starter valves rest on a common plate which rests on the idle screw; when you adjust that, it moves both stater valves. When cold, the wax unit lifts the starter valve plate to open them for more airflow (= fast idle), and when warm the wax unit lets the starter valve plate relax back to the idle screw.