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This is true, but is more of a function of the cam profile than the carb itself. Demon makes different carbs depending on your cam profile. If you have a big cam with a large amount of overlap, Demon recommends running as much initial timing as you can in order to clean up the idle. On my old Demon carb'd engine, I ran 17 degrees initial plus 18 mechanical for a total of 35 degrees. It really did help clean up the idle and the lower rpm. Probably applies equally to Holleys as well.
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My 351-W is in a street car,maybe 350hp, hydraulic flat tappet cam,carb didn't need much tuning to get it right on......
The 331 stroker is in a road race car, cam is 620+ lift,solid roller,not sure exactly how much overlap this cam has, would have to pull the cam card, but, tuning the carb took all of one day at the track with few changes.....
One thing I've noticed is the Demon carbs run better with the floats a little higher than how you would normally set them on a Holley.....
The thread starter may be "over carbed" with his combo, I've seen this all too many times........
Holley and others use this rule of thumb for calculating cfm of a specific engine combo,as follows:
max rpms X cubic inches, divided by 3456 X vol.efficency....then add 50 cfm to that final number......
On my 351-W, I'm dead on with this formula, on my race car, I'm about 40 cfm short.....but it runs like a bat outa hell........
David