A double pumper is a race carb with 2 fuel pumps, most carbs only have a single fuel pump. Mechanical secondary's means all 4 barrels open from the pedal. The alternative is vacuum secondary's where 2 barrels open with the pedal and the other 2 barrels open with vacuum.
they call them double pumpers because of the dual accelerator pumps..not because of the mechanical secondaries..double pumpers also come with vacuum secondaries
No double pumper has vacuum secondaries. Vacuum secondaries don't have a second accelerator pump thus being a double pumper. I make 900+who with a demon and have not had issues you other guys speak of and have sold a few hundred in my shop over the years. This is not a holley in any comparison.
From mighty demon web site on this exact carb: nstallation Designed for moderate 289 - 327 & mild 350 - 406 cid engines Mild 350-406. So if your running a SC on a 400 seems to me you undersized that carb. Would have been great to do that on a 327.
+starbattles1 smaller cfm carbs pull fuel faster that a larger cfm carb.. the signal is stronger to the booster because the venturi is smaller = higher velocity..
The perspective is up front: for the guy with one foot on the street, one on the track. The annular boosters lend themselves to part throttle responsiveness, and not living at w.o.t. We can assume the cam selection supports this goal as well [living below 6500 rpm]. So... for a 400, the 750 is a good choice, especially since as a blow through it will see higher flow numbers with a hair dryer force feeding it. Wish they dyno'd this to show what real flow numbers are, but I doubt he needs to tip past 780cfm.
Demon carbs are crap....many speed shops won't even stock them anymore because people complained so much about....my friend had a Demon 850 on his BBF powered Mustang....I loaned him a 850 Holler I built out of a box of parts I traded a gearset for....jetted it the same as his....car went .21 faster all night with better mph...ran both carbs back to back....
