Shown....10" Vacuum at dead idle.
At 1500 R's it dropped to 7-8"
That seems low, but I've never put a vac gauge on a single cyl either.
The reading was quite irratic at idle,.....0-15 and stabilized some at 1500 R's, ...like 8-12. The restrictor in the gauge was .030, so I added a .020 in the hose, and now it is perfectly normal w/ reaction time still ok. I'll try it at speed when the weather warms a little. But if it fails to serve the purpose, I have another place for the gauge, and my custom made ss mount will hold a tach just fine.