Trying to synchronize the weber carbs on my '76 308 and the synchrometer is reading very high (10 or more). My understanding is that it should read about 3.5 to 5. But I just discovered that the STE SK Synchrometer is reading 7 while its just sitting upright on the bench. No matter where I place it, it still reads 7. If I tilt it upside down then it goes to zero. Shouldn't it read zero when sitting upright on the bench? How do I calibrate this thing? Or do I have to throw it away and buy another one? Mine has the #118 extender.