Had this carb for a few months now, but recently the symptoms have gone from bad to worse. I rebuilt it right before I put it on, so nothing is in old condition.

Symptoms:
idle extremely high (1500-1800)
hunting idle, especially when cold
hesitation, especially when cold, especially in lower revvs
tries to die when stopping suddenly (idle problem or auto trans problem?)
above idle, things are pretty good, top end feels great, might be more waiting to be discovered though...

Not a problem now that it's hot, but I think the choke 'disengages' too fast, should I put a resistor in the wire? The idle hunting is screaming vacuum leak to me but I tried spraying starting fluid at potential leak spots and came up with nothing (spraying directly in the carb made it want to die.) The vac system is isolated from interior stuff and headlight stuff, so only: distributor, PCV and, modulator valve.

Disconnecting the distributor didn't affect idle, but I guess that's normal since there would be no ported vacuum at idle.

Any clues? It's really hard to diagnose anything when it's idling at almost 2 grand. Idle screws are pretty far in... if I'm not mistaken, do I need the next jet size down to gain useable mixture-screws? Or simple as lower float level?? Speaking of which, is it normal that setting float level is very difficult because it takes forever to come down when adjusting downward? (i.e. never! even when revved)

Was going to put it off for Tuning for Beer in VA, but it's degrading enough that I won't be able to make it at this rate! Really becoming a not-fun daily driver.

-Chris

 

Try disconnecting your head light system and see if the idle improves. There are alot of places in that system to get a vacuum leak. Just a thought.

 

[QUOTE= Or simple as lower float level?? Speaking of which, is it normal that setting float level is very difficult because it takes forever to come down when adjusting downward? (i.e. never! even when revved)



-Chris[/QUOTE]

you got alot going on there lets start with float levels and transition slots....adjust floats so they are at the middle rib and no it shouldn't take forever to come down,a drive around the block should do it....and your transition slots are set to what? a good starting point for idle mixture screws is 3/4 turn out from closed, mine are at 5/8 out. and you do not have the fast idle screw under the choke set to give you a fast idle to you? perhaps it set incorrectly...try backing off on that all the way.

 

Transition slots are at .020 (square) as per Lars paper. I originally set the float levels to the lower slot (also Lars paper rec.) but I should probably double check that they're still there.

 

According to bg inst. video a high idle that wont go down indicates a lean condition. Check transfer slots are square/.002 and richen idle mixture. Lowering bowl level to bottom line helped mine also.

 

[QUOTE=bobs77vet]Bob, do you have mechanical or vacuum secondaries on your speed demon?, and what adjustment screw are you adjusting when you check the transfer slot on the secondaries for .020 to match the primaries for balanced four corner metering. My float levels are at the bottom line and in talking with Lars, the Eze Idle through the carb stud should be closed and not used, seems to make adjustments more confusing....

 

vacuum secondaries , the adjustment screw for the secondaries is a set screw that is hidden under the electric choke, and yes close the idle eze ....i have moved back up to just below the middle rib in the float site glass

really the adjustments are kind of straight forward but you need to repeat them twice in order to get stuff squared away,. the first time is rough settings the second time is for fine tuning and the last thing you do once all a/f ratios are correct is fine tune idle by adjusting the transition slots equally for final idle speed

 

I know this may sound a little strange, but what CFM of carb are you running...? And what are the cubic inches (and a quick summary) of your cam profile???

 

Dave (Cali, 68) has been chasing Demons out of his Demon since he got it. Maybe he can tip you on this.

 

Speed Demon 750cfm no IdleEez vac secondaries, 350ci (a little over 9 CR), CompCams 268HE (.454/.454 218/218) I'll include my signature, I think that contains some useful info.

"Too much carb!" I'm sure some will shout, but I'm of the school of thought that there's no reason I can't tune it to work for my combo. I believe Lars would back me up on that.

I just wish I had a waking hour of the day to devote to tuning my car. Full time student plus full time job plus 2 weekend work trips in a row equal very little sleep.

-Chris

edit: oh yeah, checked and I did not see a fast idle screw? The only screw on the passenger side in the inconvenient little alan head adjustment for the secondary transfer slot. Maybe I missed it, the engine was running so I was trying not to stick my head in the fan.

 

do you have an electric choke? if so its right next to that hex head set screw for the secondaries and pointing at the electric choke...

this is what i welded up to to deal with that set screw

[IMG][/IMG]

[IMG][/IMG]

 

I found the adjustments easy also after a few times, I removed the electric choke. the Idle Eze was confusing but after talking to Lars I'll close it this weekend and try some further tweaking...I adjust the transition slots from the the top with a feeler gauge/scale. Once I set the primaries at .020 then take a measurement to the top of the butterfly I can then reference that measurement to the secondaries butterflies and have a balanced reading for all four corners....

 

i think i understand what you mean but just out of curiosity are you measuring the distance that the butterfly is "off from the side of the carb"?

 

Correct Bob, after the initial setup with the carb off the manifold and transer slots set at .020 I reference from the butterlfy either top or bottom edge, measure and log the distance to the top edge of the inside. I now have a mesurement to reference when the carb is mounted and don't have to remove it to check for .020. I can now adjust the transfer slots and measure all four butterflies so they match...

 

great minds think alike thats also what i

 

That's "Shore Power" for ya...

 

i lost track of the other post....but let me know when that "cruise in" is at the sports authority in brick

 

Will do.... we'll exchange telephone numbers....

 

Well, I would disagree with that school of thought. If you had a Holley 750, yeah... But a Demon? No.

You need a minimum CFM to make the idle circuit work correctly... And my opinion is that your engine (which is only slightly warmed over) is not drawing enough to do the job...

I had a 396 BBC that was punched out to 414, with a monster cam, and was using an 850 Demon... And I experienced the same symptoms as you are... I finally switch to a 750, and the problems went away...

Good luck......

 

It's ALL in the tuning....