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Discussion Starter #1
AAAARGH:mad: I bought a motometer synchronizer for my weber 45s. Previously I had synchronized them manually by the inspection holes (maybe that is not what they are called but they are a plug that when removed reveals two tiny holes that you can shine a light down and see the throttle plates) and all was running well.

Last week I adjusted the float level to spec (8.5mm) and the car was running really well. The synchronizer came without the adapter for the Alfa airbox, so I removed it and just stuck it straight into the throat. I was surprised that the meter was showing a 2 kg/hr difference in the airflow rate:eek:
Well, I adjusted them until they are even and readjusted the idle mixture and I immediately noticed that I now have a miss on #2:mad: ***!!
I then pulled the plugs and cleaned them with my fine gauge wire wheel. They were a little fouled, but not horrific. So I put them back in and got the mixture adjusted so that we are firing on all 4 and took it out for a drive. It drove fine...until I pulled into the driveway when it started to miss again!!

I don't get it:confused::mad:
 

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The synchronizer came without the adapter for the Alfa airbox, so I removed it and just stuck it straight into the throat.
Assuming that the carbs are softmounted, then herein lies the problem. The airbox, along with the carb support rod, act to hold the carbs in a fixed position relative to each other. With the airbox removed, the carbs can 'flex' independent of each other which makes proper synchronization virtually impossible since reinstallation of the airbox will affect the carb sync. In other words, proper syncing of the carbs without the airbox (or other permenant carb support device) installed can't be done.

I use the cylinder drop method to sync the carbs. This requires nothing more than a screwdriver and a good ear (or an electronic tach). With the valve clearances, cam timing, dwell and ignition timing in spec, warm the engine and note the idle RPM. Close the mixture screw for cylinder #2 on the front carb (counting the turns) and note the change in RPM of the engine. Return the screw to it's original position. Do the same for cyl. #3 mixture screw on the rear carb. The RPM drop needs to be the same for both cylinders. If it is not, slightly turn the carb sync screw toward the carb that has the lesser effect on RPM. In other words, if the RPM drop on cyl. #2 is 100 RPM and the drop on cyl. #3 is 20 RPM, the front carb is doing more work. Turn the sync screw counterclockwise (toward the rear carb) then repeat the drop test. When the RPM drops are the same, the carbs are sync'd.
 

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You might try synching the way Luigi and Marcello used to do it.

Special tool required = piece of 3/8" heater hose about 14" long.

Stick one end of hose in one ear, and the other end in each of the four carb intakes (successively).

It's REAL obvious from the sound when things are right, a LOT faster than any other methods, and likely as accurate as any method.

Greg
 

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Discussion Starter #4
Papajam, the carbs are indeed rubber mounted. I never thought of that effectng the reading, but obviously I was wrong.....

To update the situation, I unscrewed the progression hole plug and shone my 21 LED flashlight (daylight in your hand) and watched the throttle plates. I adjusted them until I could see that they were all passing at the exact same time. Bearbvd, I think that this is probably just as fast as the old hose method. I have heard of doing that for SU carbs on limey cars;)

Long story short, I spent some time with it yesterday and now it is running better than ever:D:D
I still might order the adapter to use the motometer on the Alfa airbox. I doubt it will make a huge difference, but I think that there are still variables like throttle plate seat wear and the like that could be corrected for with the use of the airflow meter.
 
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