Low Vacuum

[sputnik 440]

How about the level of fuel in the float bowls? I run my DP850 4150 with the level just slightly above the center mark. If it is too high, you will run rich. In my experience, this had an effect on the vacuum. It is always the first thing I look at and set. You might check to be sure your floats are fitting properly and not deformed or leaking.

 

[StreetWedge65]

Found several issues that caused the low vacuum. Looks as though the Demon carb gaskets compress significantly more than the Holley gaskets. All most to the point of restricted flow. The secondaries were slightly open. The secondary set screw was set from the factory about 0.028" open. Re-set initial timing to 23°. At 18° vacuum was 4"-4.5"Hg. At 23° it is a steady 6"Hg vacuum. 6"Hg seems low but with the over cam lap, I guess it is what it is.