When we do motorcycle carbs and throttle bodies, we use a vacuum gauge and drop the RPM as low as possible. Synchronization affects the idle quality most.I have a specific need. I want to make adjustments to the butterflies on a 2-barrel Weber carburetor and flow each barrel separately. The idea is to synchronize the 2 barrels. The synchronizing is done at idle which is a very low flow rate. With the carbs on the engine and the engine running I use a BK 1-35 kg/h synchrometer. The reading is about 6. I’m doing this to 4 carbs. On 2 carbs the barrels are synced, one carb is slightly off and one carb more off. I am thinking of building the PTS flowbench with one blower and a variable controller to get this low flow rate. Am I going in the right direction? Thank you in advance for your comments. Now that I'm a member I will start reading all the info.
Tom
If you've got vacuum ports for each venturi of the carbs, you could use a shop vac and a home made water manometer with as many columns as you wish. Keep in mind this one fact though. You can bench synch carburetors to be equal but the doesn't mean when they're mounted on the live engine they will remain equal from cylinder to cylinder. Port velocity variances can and often do occur.
The most accurate way is to balance them on the live engine.