One cylinder pulling in slightly more air than the others Options

[tornik550]

I was playing around with my snail gauge- trying to get my carbs adjusted (dual weber 44 idf). I found that when my carbs are synced and engine is running well- cylinder 1 pulls in slightly more air than the other 3 cylinders. At idle- the snail gauge reads 6 on cyl 2,3,4 and reads 7 on cyl 1. I recently adjusted the valves. I do not know what the numbers were prior to adjusting the valves. Is that an issue and if it is, where to I start looking? Can this be a sign of a tight valve.

FYI info- engine is a 2258, new rebuild with about 100 miles. Car runs great. Engine temps are great.

[yeahmag]

Typically there is an idle air bypass screw that you use to bring all the barrels *up* to the highest one.

[McMark]

Unless the high cylinder idle air bypass is already out a bit. They're the ones with the little lock nuts. Make sure the high one is seated fully and if that doesn't fix it, bring the others up. If the idle is then too high, adjust with the idle stop screws.

Also, if the air bypass screws won't fix it, the throttle plates may not be sitting straight. Fairly easy to fix, but a bit of a PITA because you have to pull the carb off the carb to deal with it.

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.redlineweber.com-419-1343361578.1.gif)

[aircooledtechguy]

Also, if the air bypass screws won't fix it, the throttle plates may not be sitting straight. Fairly easy to fix, but a bit of a PITA because you have to pull the carb off the carb to deal with it.

I've seen this twice in the past couple months on new carb sets (both 44 Webers). (IMG:style_emoticons/default/dry.gif)

[tornik550]

I played around with the air bypass screws and was able to get all the cylinders pulling the same amount of air- however now I cannot get my idle below 1500. I did ot mention in the original post that I had recently replaced the butterfly plates prior to me having this issue. Looks like I now need to remove the carbs and make sure the plate is seating properly.

[rhodyguy]

did you readjust the idle speed screws? the air bypass-idle speed screw matter is discussed on p31 of the CB manual.

k

[tornik550]

did you readjust the idle speed screws? the air bypass-idle speed screw matter is discussed on p31 of the CB manual.

k

I backed out both idle speed screws all the way and it still idles at around 1200. The only two weber books that I have are the Haynes Techbook and "The Weber Tech Manual". I read those and followed everything I could find.

[aircooledtechguy]

It sounds like the throttle plates are not properly seating in the bore.

[McMark]

Check your timing. Too advanced and the idle will rise.

[tornik550]

I just went outside, removed the carb that had the high air flow cylinder. Both plates APPEAR closed however, as an experiment, I poured gas down each carb main bore (as stated- the carb was removed from the engine). I watched to see how quickly each side would drain when the plates were supposed to be completely closed. Both sides were slow however I could see air bubbles coming up on the high flow carb- to me this indicates that plate wasn't closing completely.

Considering that both sides appear completely closed- however do I adjust the plates to make sure they are completely closed? I did play around with the plate and then retry the experiment. I am not getting any air bubbles now however it still did drain a bit quicker than the good cylinder.

Also, I do think that I am about 2 degrees too advanced.

[Elliot Cannon]

Typically there is an idle air bypass screw that you use to bring all the barrels *up* to the highest one.

I thought all the air bypass screws should be closed. (IMG:style_emoticons/default/confused24.gif)

[mrbubblehead]

did you readjust the idle speed screws? the air bypass-idle speed screw matter is discussed on p31 of the CB manual.

k

I backed out both idle speed screws all the way and it still idles at around 1200. The only two weber books that I have are the Haynes Techbook and "The Weber Tech Manual". I read those and followed everything I could find.

[mrbubblehead]

did you readjust the idle speed screws? the air bypass-idle speed screw matter is discussed on p31 of the CB manual.

k

I backed out both idle speed screws all the way and it still idles at around 1200. The only two weber books that I have are the Haynes Techbook and "The Weber Tech Manual". I read those and followed everything I could find.

was your linkage dissconected when you backed out the speed screws?

[tornik550]

did you readjust the idle speed screws? the air bypass-idle speed screw matter is discussed on p31 of the CB manual.

k

I backed out both idle speed screws all the way and it still idles at around 1200. The only two weber books that I have are the Haynes Techbook and "The Weber Tech Manual". I read those and followed everything I could find.

was your linkage dissconected when you backed out the speed screws?

Yes

[mrbubblehead]

did you readjust the idle speed screws? the air bypass-idle speed screw matter is discussed on p31 of the CB manual.

k

I backed out both idle speed screws all the way and it still idles at around 1200. The only two weber books that I have are the Haynes Techbook and "The Weber Tech Manual". I read those and followed everything I could find.

was your linkage dissconected when you backed out the speed screws?

Yes

hmmmm. and all bypass screws were seated?

[McMark]

Did you use a flashlight behind the carb? Also look at them from the bottom. Eyes on the bottom, flashlight on the top. Usually I can see a variance pretty obviously.

It just occurred to me, but you might also be able to use a shop van and 'the snail' to test the throats. The shop van will pull the same air volume, whereas the engine may not.

Remember that if you fiddle with the plates, you should reset the carb adjustments to the beginning and start over.

[tornik550]

Did you use a flashlight behind the carb? Also look at them from the bottom. Eyes on the bottom, flashlight on the top. Usually I can see a variance pretty obviously.

It just occurred to me, but you might also be able to use a shop van and 'the snail' to test the throats. The shop van will pull the same air volume, whereas the engine may not.

Remember that if you fiddle with the plates, you should reset the carb adjustments to the beginning and start over.

Flashlight was a great suggestion. After I had readjusted everything, I used the flashlight and found that the high flowing cylinder was way off.