Got a holley carb # 3018 I think. I rebuilt it and and my idle air mixture screws do absolutely nothing. I have a monster cam and only have 4 inches of vacuum. Will opening the back blades a bit more help in closing the fronts a bit more to make the air screws work? I've had plenty of holleys in my cars and have never had this happen. BTW I took my BG 850 street demon off and the adjuster screws worked fine on that carb. Any ideas?
BTWW, I put the gaskets on correctly. Stacey

If you only have 4" of vacuum your powervalve is opening and dumping in more fuel, second, you need to drill holes in your butterflies I would start with a 9/32 drill bit and go from there, drill the side that the idle circut is on. also there could be a leak somewhere from the intake/carb. Another thing to check for is a warped mainbody/metering block. did you get the carb brand new or used? umm...what else...yes opening up the secondaries will help, also what is your initial timing set at? if's a big cam it would probably like 16-18* initial timing, that will help out too. I pull about 7-8" of vacuum and I run a 4.5" pv in front, plug in rear, i drilled the butterflies front and rear with a 9/32 drill bit, cracked open my secondaries, and run 16* initial timing, fix'd the problem right up. Also making the engine starve by having the idle way down does sound awesome, but you probably should idle it up some. this could be why you only have 4" of vacuum. My big block has 245/255@.050 duration cut on a 110lsa and I idle it at 1100rpm, hope this helps

If you choose to try the holes in the primary,start with a 3/32" hole not a 9/32". Have you thought about putting a more reasonable size cam in? Your best ET doesn't indicate a need for a "monster" cam.

Thanks for the input. I have a 2.5 power valve. Idle at 1100. Engine is a 396 bored 60 over with 10.5 to 1 and can spin past 7 grand. It's built for it. Unfortunately I don't know what cam is in it but do know it doesn't come alive till about 4 grand. I just never had a carb that the screws did nothing. All the way in, nothing. All the way out, nothing.

Just a guess here, but perhaps at that idle rpm the primaries are doing everything - the idle circuit is not doing anything, so the screws yield no change. I am curious if you are you using a vac advance distributor (manifold vacuum?)?

Thanks for the input. I have a 2.5 power valve. Idle at 1100. Engine is a 396 bored 60 over with 10.5 to 1 and can spin past 7 grand. It's built for it. Unfortunately I don't know what cam is in it but do know it doesn't come alive till about 4 grand. I just never had a carb that the screws did nothing. All the way in, nothing. All the way out, nothing.


What about the timing? that could help a lot the more advanced the more rpm, the lower the butterflies can be, the more the idle circuit is in control. also I read that oversized main jets can introduce more fuel into the idle main well and cause an overly rich idle. if it doesnt come alive til 4grand I would drill the butterflies, the holley ultra hp series comes standard with all 4 drilled, it sounds like you need to lower your butterflies so the idle circuit is in control, I'm not a pro carb rebuilder but I did exactly what I wrote and it fix'd the exact same problem on my big block. The holes allow more air to flow into the carb cause a low vacuum motor the atmosphere isn't much diffrent above and below the carb that's why you have to open up the primaries to get it to idle, then too much of the idle slot is exposed and no idle control. hope this helps!

My timing is msd with vac can conn. at manifold. Initial is at 14. Trust me I did everything to get 4 inch pounds up from 2 at 900 idle. At about 1500 RPM's I can squeeze 10 and at about 2500 I can get maybe 15.
My primary jets are 77. Maybe I'll try opening the backs a bit more to lower the fronts. Funny thing is, I have a very nice idle without playing with the jets. Not too smelly at idle either.

The engine was purchased through our TC ads and is a 69 396 complete, new rebuild, and broken in. ( I took what I could get.) That is why I don't know what cam it has. The engine was in a 4 speed car.

okay, so then if all of that checks outs then there are two possibilities. you either need more air introduced into the motor at idle (ie: holes in the butterflies) or you have a leak some where, maybe it's on the bottome side of your intake ports into the crank case? could be from milled heads and not milling the intake, or a warped mainbody/metering plates. That's gotta be it. Like I said if there's no leak the diffrence in the atsomphere from over and under the carb isn't diffrent enough. so you motor isn't pulling in enough air at idle that's why you have to open up the 'flies the get it to idle, then no idle control. I really believe it's one of those two problems. Drilling the butterflies isn't bad to do lot's of people do it, Holley does it straight from the factory! barrygrant invented the idle eaze thing, does exact same thing. I HATE carb gremlins!!!

What about the timing? that could help a lot the more advanced the more rpm, the lower the butterflies can be, the more the idle circuit is in control. also I read that oversized main jets can introduce more fuel into the idle main well and cause an overly rich idle. if it doesnt come alive til 4grand I would drill the butterflies, the holley ultra hp series comes standard with all 4 drilled, it sounds like you need to lower your butterflies so the idle circuit is in control, I'm not a pro carb rebuilder but I did exactly what I wrote and it fix'd the exact same problem on my big block. The holes allow more air to flow into the carb cause a low vacuum motor the atmosphere isn't much diffrent above and below the carb that's why you have to open up the primaries to get it to idle, then too much of the idle slot is exposed and no idle control. hope this helps!
Just wondering if you had an issue with a rich idle before you did these changes????

I have a bad smell of unburned gas at idle. I think I need some tweaking on my carb. I have my butterflys drilled, I guess I need to check PV/reduce main jets size/and lower the butterflies.

The carb you listed from what I could find is a dodge 2 barrel carb off of a 360 engine.If you have that big of a cam in a 396 14* initial is not enough timing I would aleast start with 18*.I have never drilled holes in the butterflies before,i'm sure it would work just never found it neccessary to do.Make sure your not showing to much of the transfer slots as this will effect wether you on the idle cirquit or into the main metering cirquit.

Just wondering if you had an issue with a rich idle before you did these changes????

I have a bad smell of unburned gas at idle. I think I need some tweaking on my carb. I have my butterflys drilled, I guess I need to check PV/reduce main jets size/and lower the butterflies.



The main jet thing is with really oversized jets like in the 80's 90's, an it's a very small factor in the equation. but it is possible