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Carb adjustments……… At wit’s end.. >

Carb adjustments……… At wit’s end..

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Carb adjustments……… At wit’s end..

Old 09-27-2009, 01:32 PM
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When I adjusted them last summer I did half.. Wanted to try something different.. went to 3/4. I adjust them in fire order 1-8-4-3-6-5-7-2 each a 90 degree turn on the crank starting at TDC..

Going to go with a VAC gauge in an hour or so to check idle vac.
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Old 09-27-2009, 01:47 PM
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John cranes method works pretty good also i always set hyd rollers at 1/2 turn but 3/4 should be fine as long as you were on the heel of the cam. what kind of exhaust you got on the motor
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Old 09-27-2009, 02:01 PM
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ok i have reread the thread have you checked the floot leavel if it is to high it can cause the carb to drip at low rpm and load the motor up with fuel. bottom line i am with Eddie you will find it with the vacum gage and o2. i would try the vacum gage first and see where the vacum goes in gear you may want to pick up some 4.5 power valves to try something tells me the vacum is falling to where the power valve may be starting to open
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Old 09-27-2009, 02:15 PM
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Thanks Mike.. Just waitng for the wife to get back and I am off to Kings Point to look.. I will post the VAC in and OUT of gear when done..
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Old 09-27-2009, 06:33 PM
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Vac at idle (900 RPMS) was 12-14.. in gear at 650 @8 or so.. then started to drop as the rpms started to drop.. but it back into neutral rpms went back to 800.. sounds like it is loading up.. running rough.. then rpms climb to 850.. then 900.. back into gear same thing over and over.. no matter what I do with idle mixture screws.. is 8 a normal vac in gear??
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Old 09-27-2009, 07:04 PM
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John check the float level and make sure it is good if you have 5.5 power valves you should be ok. has the motor ever backfired throiugh the carb
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Old 09-27-2009, 07:24 PM
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The way i understand power valves is if your showing 8 on the gauge you would need a #4 power valve. I think the most imporant thing would be to keep the power valve shut at idle.
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Old 09-27-2009, 07:31 PM
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The motor never fire back through the carb.. and this carb just came back from Nickerson last week.. Just ran it once.. on friday for tuning.. it HAS been to Nickerson each year for the last 3 or 4 years.. Always a great carb.. NEVER idled right.. never. not even before it went to Nickerson..
I think they put in a 5 power valve.. looks like it is stamped 50 on the side of it.. what exactly does that mean? Also the vac flickers up and down a bit on the gauge at idle.. never a solid reading.. I had always thought this was normal though.. 8 is about the highest I get in gear. @ 650.. I can get it closer to 9 if I adjust the mixture screw in to only 1 turn BUT the idle jumps to 700-750 in gear.. then comes closer to 1000/1100 in neutral..Should I try a #4 or a #3.5?

Last edited by JohnSchiavarelli; 09-27-2009 at 07:54 PM.
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Old 09-27-2009, 09:18 PM
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Dude, I feel your pain!!! I have an extensive history working with Carbs from Drag racing to Marine applications.
I have motors very similuar to yours with even more cam shaft. I had bought two new 1050 Demons, ran them on the dyno and made excellent power..They ideled great, pulled strong numbers and I was thrilled..
I put the motors in the boat at Riggs Marine. We went out to sea trial and we could not get the motors to idle with the Demon carbourators. Neither motor would idle properly. So knowing what I know about Carbs I began fine tuning them. I spent numerous hours on the phone with Demon on a daily basis.
The end result??? We could not make them work.
I promised Demon that I would not bad mouth them on the web, but this happened 1 1/2 years ago and I hate to see anyone go through the headaches I went thru..What is weird about this is that I know several people that have the marine carburators and have not had a wink of problems -- Go figure!!
So the rest of the story?? I sent the carbs back and they (Barry grant) agreed to give me a fulll refund. I now run Holley Marine 1050 Dominators. All I did was change the power valve and contoured the idle airbleeds. I am going on 2 years of flawless running - Now go figure that one...LT
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Old 09-27-2009, 09:40 PM
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Little Tommy, my friend has a similar problem with a Deamon a few years ago. In the end he took the carb to a local Race and Barry happened to be at the booth and tore down the carb. Turns out one of the bowls was improperly machined and was causing the carb to leak down, no matter where you set the bowl height.

Getting back to the carb. There's no doubt an 02 sensor is the easiest way to check the idle to see what's happening. There's also your eyes, ears, nose and other senses that can work pretty well!

Take the flame arrestor off and look down into the venturies at idle and see if you see fuel dripping from any of the boosters. then put the engine in gear and check again to see if you see fuel dripping from the boosters. this would be one of the first things I'd check for.

All these years I've never actually used an 02 sensor to set my idle mixtures and most of the time don't even need a vacuum gauge. Just ask anyone who's been on my boats how they idle.
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