Anyone Running a Demon carb?
09-26-2007, 06:57 PM
#1
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Anyone Running a Demon carb?
Any carb experts?I've got a 650 Race demon carb .Its running Rich at idle despite fuel screw mixture changes,new power valve, 2.5...talked to a few others and seems to be common...Just wondering if anyone has this problem and if anyones knows a fix...The Idle Air Bleedscrews are .070's...need larger ,smaller?
09-26-2007, 07:02 PM
#2
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RE: Anyone Running a Demon carb?
I ran a 650 mighty demon on my 86. Out of the box it ran pretty good at idle with very few adjustments. Part of the problem maybe that the race demon comes out of the box setup for large duration camshafts.
09-27-2007, 06:07 AM
#3
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RE: Anyone Running a Demon carb?
How much vacuum do you have at idle? You need to hook up a vacuum gauge and set you idle air control screw to get most vacuum, they must all be set the same. Vacuum at idle is how you determine your PV. Adjust to get highest vacuum and divide that vacuum reading in half to get proper PV.
09-27-2007, 04:54 PM
#4
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RE: Anyone Running a Demon carb?
ORIGINAL: FASTBLACK
How much vacuum do you have at idle? You need to hook up a vacuum gauge and set you idle air control screw to get most vacuum, they must all be set the same. Vacuum at idle is how you determine your PV. Adjust to get highest vacuum and divide that vacuum reading in half to get proper PV.
How much vacuum do you have at idle? You need to hook up a vacuum gauge and set you idle air control screw to get most vacuum, they must all be set the same. Vacuum at idle is how you determine your PV. Adjust to get highest vacuum and divide that vacuum reading in half to get proper PV.
09-27-2007, 07:48 PM
#6
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RE: Anyone Running a Demon carb?
ORIGINAL: 67mustang302
What's your fuel pressure, and have you set your floats? If you have too much fuel pressure or the float level is too high it will cause the same problem
What's your fuel pressure, and have you set your floats? If you have too much fuel pressure or the float level is too high it will cause the same problem
09-27-2007, 07:53 PM
#7
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RE: Anyone Running a Demon carb?
Guess my next q? is,anyone know how the Idle Feed Restrictors work(in the metering blocks)and theIdle Air Bleeds?If I remember correctly the holleys,larger Idle Air Bleeds to lean it out @ Idle(outside bleed screws)....Demons...unsure..Thanks for the responses guys...
09-27-2007, 07:59 PM
#8
D.R. THE PATHETIC DORK
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RE: Anyone Running a Demon carb?
how do you know your rich???? Ihave a friend with a 68 cougar that I tuned a 650 demon carb for them and it smelled rich out the tail pipe but when we did the afr test on the dyno at idle to our suprise afr was 13.5 to 1 not to bad for a street strip car have you done an afr test and if you think it's way to rich then jet it back also if you only have 6 in hg of vaccum then you must have one lumpy idle/camshaft with alot of duration....in that case then the power valve may not work like it's intended to if you don't have the correct size in as vaccum is what holds it shut...if you had a 6.5 like a holley stock has you'd need about a 3 to 3.5 to make it work correctly with the afore mentioned vaccum reading you have.
09-27-2007, 08:06 PM
#9
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RE: Anyone Running a Demon carb?
ORIGINAL: mjr46
how do you know your rich???? Ihave a friend with a 68 cougar that I tuned a 650 demon carb for them and it smelled rich out the tail pipe but when we did the afr test on the dyno at idle to our suprise afr was 13.5 to 1 not to bad for a street strip car have you done an afr test and if you think it's way to rich then jet it back also if you only have 6 in hg of vaccum then you must have one lumpy idle/camshaft with alot of duration....in that case then the power valve may not work like it's intended to if you don't have the correct size in as vaccum is what holds it shut...if you had a 6.5 like a holley stock has you'd need about a 3 to 3.5 to make it work correctly with the afore mentioned vaccum reading you have.
how do you know your rich???? Ihave a friend with a 68 cougar that I tuned a 650 demon carb for them and it smelled rich out the tail pipe but when we did the afr test on the dyno at idle to our suprise afr was 13.5 to 1 not to bad for a street strip car have you done an afr test and if you think it's way to rich then jet it back also if you only have 6 in hg of vaccum then you must have one lumpy idle/camshaft with alot of duration....in that case then the power valve may not work like it's intended to if you don't have the correct size in as vaccum is what holds it shut...if you had a 6.5 like a holley stock has you'd need about a 3 to 3.5 to make it work correctly with the afore mentioned vaccum reading you have.
....and smoke abit..My dominator 8896-3 on my sbc 422 C.Ididnt run this damn rich..I'm really starting to dislike demon carbs...
09-27-2007, 08:07 PM
#10
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RE: Anyone Running a Demon carb?
ORIGINAL: 8banger
A solid 6 inches @ 1000 rpm(usually go 2 inches below that but no 4's so 3.5.but anyways)..did the vaccum set..Now have a pv block in the front.and itso much more responsive on the revs..but still runs a tad rich at idle..think I need tomess with the Idle Feed Restrictors or the Idle Bleed screws in the top........
ORIGINAL: FASTBLACK
How much vacuum do you have at idle? You need to hook up a vacuum gauge and set you idle air control screw to get most vacuum, they must all be set the same. Vacuum at idle is how you determine your PV. Adjust to get highest vacuum and divide that vacuum reading in half to get proper PV.
How much vacuum do you have at idle? You need to hook up a vacuum gauge and set you idle air control screw to get most vacuum, they must all be set the same. Vacuum at idle is how you determine your PV. Adjust to get highest vacuum and divide that vacuum reading in half to get proper PV.
