Info From Barry Grant Tech
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Melting Slicks
Joined: Apr 2000
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From: Ft. Walton Beach, Fl USA
Info From Barry Grant Tech
I have a Mighty Demon 750 annular w/mech secondaries. I could not find the specs anywhere including his site and their air bleeds aren't stamped. So I called tech and he gave me the following: IFR-.036 IAB-.070 HSAB-.039 main jet-67 sec jet-75. Does that jetting seem a bit small for that carb? I haven't taken it apart yet because I wanted to get the bleed info. If it indeed does have that jetting I'll be very surprised.
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
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Melting Slicks
Joined: Apr 2000
Posts: 2,145
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From: Ft. Walton Beach, Fl USA
Tech Contributor
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From: At my Bar drinking and wrenching in Lafayette Colorado
The jetting on the annular carbs is significantly smaller than the downleg carbs - AD carbs typically have jetting at least 5 sizes smaller than the downleg carbs.
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I switched over to annular boosters on my 825 Race Demon. I have an LM-1 and the carb is tuned about as good as it gets for idle, cruise and WOT, the jetting is 76/82. Out of the box with downleg boosters it is 76/84, I could probably go to 84 on the secondary side and it wouldn't make much difference.
IMHO if those are the jets shipped with the carb they are overcompensating for the annular boosters.
IMHO if those are the jets shipped with the carb they are overcompensating for the annular boosters.
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Melting Slicks
Joined: Apr 2000
Posts: 2,145
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From: Ft. Walton Beach, Fl USA
I experimented with the IAB's going progressively smaller, .069, .067,
.065. With each cahnge the low speed hesitation got better. .065 was the smallest I have and the hesitation is almost gone. I haven't opened the carb up yet because I wanted to see what changing the IAB's would do. Acceleration (2000+) with each change was still very good.
Before the IAB experimentation I put a .035 squirter and hollow screw in and it did not help the matter at all.
Sometimes I talk too much but to make a long story short other than the slow speed hesitation under light throttle it runs extremly well.
Melting Slicks
Joined: May 2002
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From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
I am tuning with narrow band meters, they are good enough to tell you what is going on. They are deffenantly better than nothing at all.
tip in stumble is usally a lean condition or an out of adjustment pump. Try backing out on the idle screws 1/2 turn, and take a drive see if this gets rid of the stumble. The moves on the IAB is the right move to help.
Neal
tip in stumble is usally a lean condition or an out of adjustment pump. Try backing out on the idle screws 1/2 turn, and take a drive see if this gets rid of the stumble. The moves on the IAB is the right move to help.
Neal
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Drifting
Joined: Oct 2004
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From: Ontario
I just bought the same carb, 750 Annular Mighty demon. I was surprised to see the jetting so low. Right out of the box it came with 70/78. I put it on my 383 with a 248 roller cam and it ran rich! I have a wide band LM1 to montor the AF.. it smelt rich and read 12 AFR at 3500 RPM. My previous 750 holley ran with 73/81 and 13.8 AFR.
Bottom line, Lars must be correct again, annular needs less jet size.
I will downsize jets tomorrow. Even with my current rich condition I can feel the increased responsiveness of the annular immediatly.
Bottom line, Lars must be correct again, annular needs less jet size.
I will downsize jets tomorrow. Even with my current rich condition I can feel the increased responsiveness of the annular immediatly.
Last edited by Retro78; Apr 23, 2008 at 11:46 PM.
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
What is the reading at idle ? Lean it out with the idle mixture screws first to 13.5:1 and then see what it is at cruise before changing jets
Drifting
Joined: Oct 2004
Posts: 1,259
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From: Ontario
Thanks Motorhead. With the screws only 3/4 open the best I get at idle is 12.2. I cannot get it any higher. Should I try downsizing the IFR's first?
