Oddly low idle speed with filter in place

[Fourthbean]

I was removing my air filter temporarily on my engine to do some carb adjustments. I noticed a considerable jump in engine RPM, the guy I was with and I both figured the air filter was clogged. I just got back from the parts store and the seeming anomaly still exists.

The difference is from sputtering barely running to idling almost too fast and smooth as anything. Note that I do have the idle speed set quite low which explains some of the sputtering, however I seem to remember it running smoother than that.

We adjusted my timing by 3 degrees the night we discovered the anomaly, we think we moved it from 1 degree advanced to 4 degree advanced. Whether we acomplished that is up to how well we can operate a timing light .

Any thoughts on this? I wouldn't think timing would have an effect on this problem. Or is it a problem?

[MnFocus]

So when you remove the air cleaner nut and housing lid your idle jumps? Then upon reinstall begins to sputter idle roughly ?
Timing will affect idle speed -
I may be wrong but it sounds as if your upper carb gasket is bad or the carb top itself cracked or warped . Do you have another carb to try?

[Fourthbean]

Yes, you have correctly described the problem.

I don't have another carb to try, and I wouldn't be surprised if the carb was warped as it took me a long time to find a carb that would work without leaking all over the place after being rebuilt (tried about 4 from local auto parts store and another from specialty carb shop). Seems there is an inherent problem with this carb design.

This carb I ended up getting from a junk yard and worked better than any of the others without rebuilding it. Go figure.

How would the gasket being bad make the screwing and unscrewing affect the running of the carb? That one escaped me, but I am a rookie at this and here to learn .

[lunarhighway]

i might be miles off , but have you checked the floater needle?

i once had a problem wel the engine stalling on idle... turned out the floater needle didn't work propperly (that's what we concluded at the time at least...) causing the floater chamber to overflow into the carb... a little more air from the cleaner beign gone might be just enough to balance out the mixture enough so the engine can deal with it...

but i'm by no means a carb expert... i just have to deal with it to keep my car running... i once though there was sometihing really wrong with the car as it ran too fast with the air cleaner off, but it turned out i had rested the cleaner on the accelerator cable.... go figure.

[Fourthbean]

Figured it out with the help of a freind, t'was a vacuum leak. Of all 2 vacuum hoses in my car one decided to leak. I didn't help it any by also crimping it when installing my vacuum gauge...

Thanks for the help, I am just glad I won't be messing with my Carb. That's a load off my back!

[VetteOwner]

Originally Posted by Fourthbean

Figured it out with the help of a freind, t'was a vacuum leak. Of all 2 vacuum hoses in my car one decided to leak. I didn't help it any by also crimping it when installing my vacuum gauge...

Thanks for the help, I am just glad I won't be messing with my Carb. That's a load off my back!

haha yea check easy things first. vaccum leaks can be strange sometimes, probably by emoving th elid and cleaner stuff you bumped the line causing it to kink or cause a bigger leak. but no matter, its fixed now