Easy noob question - vacuum
Race Director
Joined: Nov 1999
Posts: 10,643
Likes: 8
From: Foxfield CO 1970 Convertible
Proper engine operation should result in an even vacuum reading from 15 inches to 20 inches of vacuum with 15 inches of Mercury being more appropriate for high performance type engines. 10 inches would be on the low side... 
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
For a properly tuned L-48 at idle, you should see 17 to 20" hg. Variations can be attributed to ignition timing, cam timing, cylinder pressure, and carb adjustment just to name the usual suspects.
