CarburetorsCarb discussion and questions. Upgrading a Third Gen carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
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I currently have a .029 idle feed restrictor in my 650 mighty demon. I need to decrease it by .002 which would bring it to .027. Im trying to find these on the web and its a pita and one of the only things that come close are the air bleeds. Are these the same part just used in different places. Any help would be appreciated.
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Havent called BG yet just called the local speed shop and they said good luck getting aftermarket parts from him. I looked in summit and jegs but didnt find anything in the size I need nor do i know if holley or quick fuel is interchangable with demon.
From what I can see in the on-line Mighty Demon manual, the metering blocks look pretty much like billet Holley metering blocks. Further down, under "Tuning Parts and Accessories", is "Blank Idle Feed Restrictors (10pk) 200083". Meaning you need jeweler's drill bits to make your own .027" restrictors. Whether those are the same as available from QFT, for instance, I have no idea.
Out of curiosity, how do you know you need .027" idle feed restrictors?
I bought a demon tuning book and im trouble shooting a rich condition. I cant get my carb idle screws to lean out and i have to open the butterflies more than the .020 on the primary and secondary for it to idle right. The book says in this case i have to down size the idle feed restrictors from my stock .029 to .027 so the circut returns back to normal and i can adjust my idle and fuel with the idle screws again.
It does have removeable air bleeds and i havent touched them yet. Right now im just going by what the book says. Why should i change the air bleeds before the idle restrictors?
i would be changing idle air bleeds before restrictors IMO since they're more readily available and easier to swap without taking the carb apart to change.
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I will get .071 and .072 for air bleeds and see which one works better. And I will also pickup a .028 idle feed restrictor just in case all else fails. Something has to work.
It does have removeable air bleeds and i havent touched them yet. Right now im just going by what the book says. Why should i change the air bleeds before the idle restrictors?
it is easy to do and it worked for me, I had to tune my 1090 for the idle circut and found a .001 change in the restrictor was not enough change to fix the problem, mine actually poured fuel from the idle feeds under the plates. I went from a .046 idle air bleed up to a .070 to clean it up. Very easy way to tell is find another set of air bleeds that are larger in the intermediate circut if you have one and swap them. mine had .040 stock in the idle .070 in the intermediate and .029 in the high speed circuts..so I just swapped until it ran good at idle then drilled my stockers to .070
So are you telling me I have to get a kit of 30 different air bleed sizes and swap them all until one of the works the best. Going up 1 or 2 sizes isnt gonna cut it?
buy one air bleed set and slowly drill it up, when you find the size that works best just buy that one.
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So are you telling me I have to get a kit of 30 different air bleed sizes and swap them all until one of the works the best. Going up 1 or 2 sizes isnt gonna cut it?
no..I`m telling you to swap the bleeds from another circut to verify the results..as long as the bleeds are bigger it will make a difference in the mixture screws. In my barry grant tuner book it is page 82-85 roughly that talks about tunning the bleeds and restrictors, that section is for the kings but it applies to all holley based BG carbs, the book I`ll admit is lack in direction and difficult to follow but the info is there.
I havent tried swaping anything yet I just bought some air bleeds from BG and Im going to try .071's and .072's and see if that helps out. I also noticed that after my car has been sitting the fuel bowls look like there empty. So im thinking maybe I have a blown power valve that might have been leaking this whole time and creating my rich condition also. Im geting to the point where im just going get a rebuild kit and go threw it myself because BG guys suck at assembling these carbs. That is sad when the carb only has 100 miles on it.
I just stepped the air bleeds up to .071 and I got a little more adjustablity out of the idle screws and now I can use the idle eze alittle bit. I also have the idle screws out 3/4 on all 4 corners. I think im going to step up the air bleeds to a .073 and see what happens.
Another quick question. Right now I have my fuel bowls set in the middle of the sight glass right at the 2nd line. Would dropping the the floats down to the 1/4 mark or 1st line of the sight glass lean out the carb ?
I'm folloing in your footsteps I think. Any luck with the idle air bleeds or idle feed restrictors?
Yes i have had alot of progress since last year. I first tore the carb down and found nothing wrong internally so I just replaced the metering block gaskets and delt with it. I tried changing the floats to the first mark and the car idled better but driveability suffered greatly.I put both pri and sec back to the middle mark and the changed out the idle air bleeds. That helped and i got more feedback out of the idle screws. After that i tried the idle eze again which wasnt a help before but now is. The last thing i did was replace my base plate gasket and it was like having a different carb. Everything worked 10 times better. Car still idles slightly rich but nothing like before. I have drove the car for all of 2009 and just put it away. I have no complaints about my 650 mighty demon.
Hmmm...the base plate gasket? Sounds like I need a complete overhaul for good measure. Don't see how this remanufactured/refurb from eBay could have problems since I purposly didn't buy a new Demon due to the QC issues but one thing I have learned is you can never assume.
These Demon's seem to be just pig rich from the factory. I know the idle air bleeds are a big part of this so that is something I must change. I am running a cam with a good amount of overlap adding fuel to the fire (so to speak).
Unfortunatly, I am running a Speed Demon so that entails drilling them out. If I went to all this trouble I would just want to heli-coil them or something so I could run the screw intype. (Is this even possible??)
Did you ever mess with the idle feed restrictors at all??
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I got this rebuild kit if it helps http://www.jegs.com/i/Barry+Grant/132/190004/10002/-1
I also have a large cam with a ton of over lap so I know how you feel.Are you sure you dont have replaceable air bleeds ?And just a thought I think you have a 750 speed demon if I remeber right ? If you do i think its too big for your application. A 650 might have worked better.
Well, I enlarged the IAB's a bit and put a strand of speaker wire in the IFR's to restrict them a bit more and it has seemed to help only a small amount. I need to tune it very much so, however, it is still smelly rich at idle. Now I have a few more hesitation problems (which I 100% expected) during normal driving.
Might have to take it back apart and go bigger on the IAB's.
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