Found the reason for my too fast idle on my 250 chev with dual carbs. Chinese air cleaners. I bought the cheapest ones I could find on eBay (I know, that's the problem). What are you running, or what did you have to do to get the idle down on yours? My Idle screws are backed all the way out. It tends to run on, after shutting the key off. Never did this when I had mis-matched carbs (one manual choke & one automatic), but now I have 2 BCs & it idles faster. Took the air filters off, & it idles much slower. Did a search, but probably wasn't using the right terms. Ideas?
Obviously the air cleaners were too restrictive and causing the car to run rich. When you take them off it leans out the mixture and it idles better. Like running with the choke on a little.
Yes, obviously. I guess I need to state things clearer. I know the cause, now I need HELPFUL suggestions. I will also state, that I don't want to spend huge money for a low buck car. Just wondering what everybody else uses, or if they modified the cheap ones to work somehow. What type are you using, that seem to work well & don't cost more than the car?
How about putting a taller filter in them? This is where a picture of what you are starting with would help.
Paper element. Just cheap Chinese junk. Didn't think they would be so restrictive. Is there less restrictive paper elements that you guys use? Or did you just splurge for some high dollar thing that I don't know about? Still not sure why it worked on the mis-matched carbs either?
if it is a low buck you obviously must not care about motor ingesting dirt simple do not put filters on it.would you use sandpaper to wipe your butt?after all it is paper.good filters have a reason for cost research and reputation
Look at the surface area of the louvers on the element covers. Now compare it to the round opening of the top of the carb. Does it let enough air in? It doesn't look like it. Plus if that small element gets a little bit of crap in it think of how restrictive that will be. I think you need to get a filter with a bigger diameter for starters, and no restrictive cover over the element.
I've run those same air cleaners on a tripower with no issues at all. You may need to look at the filter element themselves.
The louvres are to small and not opened up enough Try making the louvres wider and bigger If you f’up that marvellous Chinese chrome just paint them Remove the junk paper element and try foam compressor elements for more air flow You can also make velocity stacks out of cheap chrome tail pipes and stuff some steel wool mesh or foam in them
I have the non-louvered version and Chinese (Mr. Gasket) air filters on my significantly hotrodded 250 (major head work, roller cam, etc.). No issues here. I feel like we're missing info at this point.
When you say 'idle screws' do you mean idle speed screw or idle richness screw? Sounds like an odd vacuum leak. With filters off the air enters thru the top and kinda idles - we know it really won't 'idle' because the idle screw is backed out so that means something else is going on as well. With filters on the air enters via vacuum leak below the throttle blades causing it to run lean at higher rpm. If you idle richness screw is the one backed out then thats a vacuum leak right there. But, bein an hot rod and all it I might be wrong, just a guess.
Maybe missing the point but if you have all that work, parts and money in your engine why wouldn't you want the best or better filter set up you can use? Just wondering.
I would think restrictive air cleaner= low idle. Choking off air. How does less air raise idle? Or you just couldn't turn it down and Get a correct idle? Sent from my LG-TP450 using The H.A.M.B. mobile app
Idle speed screws are backed out completely, so they are not touching the little cam thing. I don't know the technical terms. Thanks @VANDENPLAS for the good suggestions. And, thanks @oj. I will look for leaks. I realize what these are, but hoped they wouldn't be a hinderance. First plan was to make something a little different, but it was too easy to click a button & have these show up at my door. I did rebuild these carbs, & I'm no expert. They seem to work good until the filters go on.
Check here for filters by size, FilterBySize.aspx Once you click on the filter you want to see, it will give the CFM it's made to work with. A stock 1970 Camaro with a 250 used #42083 air filter, 2" x 9.718" and 65 CFM capacity. Yours are likely less then 4 or 5 cfm each!
I'd agree that the air cleaners are a bit restrictive but a restrictive air cleaner SHOULD slow the engine down because it isn't allowing enough air into it rather than speeding it up. I've done a lot of tunes ups on engines with restrictive stock air cleaners that I had to raise the idle speed after putting the air cleaner back on but have never had to lower the engine speed because the engine speeded up because of the restriction. You have another and bigger issue going on with the carbs/intake that the air cleaners are bringing out when you put them on. No restriction =it runs fine / raised restriction it speeds up is just flat backwards to what it should be if the engine is actually set up right. You could cut a couple of metal disks out that would replace the chrome bells to lower the air restriction to see if that changes it. but it won't fix the original problem.
The assumption in your question is that the filters I'm using are somehow inferior. I haven't found anything in their functionality to indicate that.