Any suggestions on what else to try appreciated!

I just got done doing a retro-roller conversion on my 400. It's a Comp XE288HR cam. 236/242 duration at .050, .510/.540 lift, 110 LSA.

I've got a 650 Speed Demon mechanical secondary carb with "idle eeze". It's never been right. It idles pig rich to the point the car smokes and burns your eyes. I've tried adjusting it according to the "Idle eeze" instructions:

1. Set primary throttle blade transfer slots at .020 (square)
2. adjusted the secondary throttle blade to just barelt hide the transfer slot.
3. adjusted the "idle eeze" screw in the air cleaner stud hole to 1 1/2 turns open.
4. Adjusted all 4 mixture screws 1 1/2 turns out from seated.
5. Float levels at or below midway in sight glass on fuel bowls.

I put the carb on the car, and start the car. Idle is at 1200-1300 rpms. I adjust each mixture screw in 1/4 turn at a time, continuing if rpms increase. I continue to adjust each screw in a little at a time until I can hear the engine starting to sputter and rpms decrease, then I screw out 1/4 turn and sputtering stops and it runs smooth again.

I then try to adjust the "idle eeze" screw in to lower down to idle rpm (Looking for 800-900 rpms) - but - I can screw the idle eeze all the way in until it's seated, and I can't get the rpm to go below 1000-1100 rpm's!! - And it still seems to run rich!

What am I doing wrong???

I've made sure the squirter arms are adjusted right, see no fuel pouring in anywhere when it's running, set timing at 19-20 degrees advanced (where it runs smoothest), and even tried backing timing off - same results.

Off idle and WOT it's got a TON of power, but at idle it's a bug sprayer!! I'm at wit's end with this "Demon" carb......to the point that I'm ready to send it back to them. - HELP!!

 

No one huh???

 

Well this probably doesn help much, but after fighting with my car the last couple months, I finally bit the bullet and took it into a local shop that I knew worked on older musclecars. Couple hundred bucks later the car runs the best it ever has. By far the best money I ever spent on the car. It's an absolute beast right now.

I know for mine he had to rejet the carb to 72/72. I think from the factory the Demon was 70/78.

 

Well, you may not believe this, but that's just what I was thinking....just take it somewhere it can get tuned right. 200 is a bargain if it runs right - to me at least. I had 80/94 jets in the carb when I got it!! Thx for the response though...nice ride BTW!!

 

yes it probly dose run great, but do you get the rpms you should with those 72 jets? the reason I ask is because that is not realy a steet cam I have a solid in a 327 that will not rev out if I idle below 2500 rpms, as the power band drops in at 4200 rpms.

just

Gb

rick king

 

are you sure that the carb is a 650. 80/94 jetting is very big for a 650. my 825 mighty demon had high 70s jets in the primaries and low 80s in the secondaries. judging from the jetting i would say its a 950.

 

If the main jets affected your idle, you had something seriously wrong.

I'm not familiar with Demons and their idle eeze, but the main vs. idle circuits concept is the same regardless of the carb.

 

Yeah, I realize the jets have nothing to do with the idle circuit....I was pointing out the lack of tune the carb was in when I got it. It's a 650 allright.

It had those huge jets in it when it was originally dynoed. It may have somehow made power with those huge orfices then, but I had to seriously jet it down when I dropped it in my car.

If it would just idle w/o dumping gas, I'd be happy with it....

 

how much vaccum do you have? is it a possibility that the power valve is the wrong size? im not a carb expert, but on my 600 holley I ran it about 2 turns out on the idle adjustment screws... I say if the car runs good with idle mixture and idle ez screw at factory spec, just lower the idle by the throttle position screw... as far as the richness.. screwing the idle and idle ez screws in is going to allow less air in right? if your eyes are burning from gas fumes shouldnt you be adjusting them outward? I would try 2 turns out on all 4 corners, then idle ez at factory and changing the throttle position screw..
good luck hope that helps-chris

 

Jeff I have acctually have the same idle problem you have and I can not figure it out. I agree on the whole shop thing and I called dons and talked to jason. He is willing to do the tuning in or out of work but needs 2 weeks to do it out of work and if you wanna do it at the shop weekends are best. He told me it would cost roughly $100 not sure if that is home or shop price though. This is the way Im gona go cause this demon is driving me nutz! Every time i get one thing right on the carb somthing else is wrong on it.

Through reading a few tech artices and some of the print on demon and holley carbs I read it says to set the transfer slots equaly for cars with an idle of 1000 rpms or more and unequal for a lower idle. I dont really remember how it said to do the unequal adjustments though but I will give you a call sunday afternoon to discuss what I re-read.

 

that "idl-eeze" option on the demons is BS anyway, it only helps a little on extreme (and i mean EXTREME!) camshafts.

discussed recently on camaros.net, had the same problems over there.

even their advertisement says something about big cams.

WARNING, those demons always have metal waste in the carbs, clean them out first before using.

the final check at demons is plain out ridiculous.

Not just my experience, many ppl complained about it.

 

Yes, I finally found that info in the "Added Idle-eeze info" while checking thier website. You won't find it in the main instructions. That "added info" instruction didn't come with my carb when I got it. Turned out it doesn't matter anyway. I set the primary transfer slots at .020", and barely have the secondaries shut off like it says to with the idle eeze open one turn. I adjust the 4 corner air/fuel mix screws at each corner about 1/4 turn at a time until I get a raise in rpm's. Then I back down 1/4 turn. I end up idling at about 1400 rpms, I then screw the silly "idle eeze screw in and it doesn't do anything. I can fully shut it. My only option at that point is to screw with the the transfer slot setting and close it a bit in hopes I can get a reasonable idle - say 800-900 rpm's.

When I do that, it either dies, or every time I blip the throttle, it won't return to idle and die instead. I run around 14" of vacuum, 17-19 adv. base timing at idle and have a 6.5 PV in it now. I spoke with Tony a week or so ago. Just got back in town and calling them tomorrow to check this Demon POS out..... Something's gotta give.....either this carb is gonna work or it ain't, then I'll get something that will work. I have WAY too many hours tweaking this and getting NO WHERE..

EDIT: BTW, thx for the suggestions all, but I've tried different PV's, float level settings etc. and no difference. And I've tried adjusting the carb with the idle eeze open or closed and it doesn't seem to do much.

 

I don't know which demon you guys are running but i have a speed demon 750. lol after removing the base plate to break the idle eze screw loose so i could adjust it i too have found no difference ( negligable) in its adjustment.

for what its worth i find that the larger the cam you have the high idle this carb likes.

my lu-snot-i cam with 234*/244* duration @ .050 liked to idle no less than 1000rpms and still keep throttle response. Any lower and my car would back fire, black smoke, stumble and die

 

what i said...