no control of idle mixture screws

[1bad79]

hi everyone I have a 17058253 I modified for my olds 455 in a g body cutlass I got it running in the car for the first time this week I notice its very rich at idle and even if I close off the mixture screws it still idles? I don't see any dripping at looking in the primary side at idle, and it starts good cold and warm I don't have a a/f gauge but will have something today yet im sure I screwed something up not sure what and im searching for what recipe I used could it be leaking internal from some where? im working on it some today in my shop so if anybody has any ideas let me know ill check back in a while hope fully with more info thanks steve

[77cruiser]

I had an issue with a carb I did & it was coming from the secondaries, I think one of the air bleeds had some crap in it. Something to check.

[carmantx]

Provide some details on your modifications to the Quadrajet and your engine.

[1bad79]

I can't find what I did to the carb i had a sheet I made with all the sizes of what I modified I know I opened the idle circuit slightly opened the mix screw holes up added bypass air the engine is 461 chi aluminum procomp heads 9.985-1 compression and I can't find the cam card I'm looking for it but I bet it's with the sheet I can't find the cams not to wild I can tell you that but I was looking at it tonight and noticed Leak around the acc pump rod and top gasket so I have something going on so I'm going to pull it this week and Inspect and recheck what I did to it

[Cliff Ruggles]

If fuel is getting up to the accl pump hole the N/S assembly isn't holding (flooding).  I'd correct that issue first, then re-evaluate the carb.

I can't provide any help at all otherwise, without all the engine details, and exactly what was done to the carburetor.....Cliff

[1bad79]

found the cam card howards cam intake .560 278 duration exhaust .555 282 duration lobe center 110 intake c/l 106 the cam was degreed in 4/7 swap cam if it makes a difference the other engine info is above  idle tube .038 down channel .055 upper air bleed .067 lower air bleed .067 bypass air .059 hole under mixture screw .089 74 jets 44 primary rods DA secondary rods 1/4 inch float setting  n/s was vacuum checked along with 3 other ones and none hold, I tried with the top off  to watch what happens and at about 2.5 pounds it wont hold,all the parts came from cliff about 3 years ago so they have been sitting along time, maybe the rubber tip dried out on the needle? so I guess I need a needle and seat for sure then retry, i am running an electric pump with a bypass regulator at 4.5 psi is this to much pressure? let me know if mor info is needed thanks steve

[Cliff Ruggles]

I'd add a little more idle bypass air and correct the flooding issues and you will be fine.

I've never seen one of our Viton needle tips "dry out", and we've had next to no issues at all with them to date.  You might try lightly smacking the seat with punch and spare check-ball, or replacing it with a new N/S assembly.

Once the flooding issues are fixed, then you can effectively evaluate the carburetor and tune it for the engine if/as needed.....Cliff

[1bad79]

im going to work on it tomorrow, thanks for the response cliff  thanks, steve

[1bad79]

fixed up the n/s and went .104 on the bypass air seems to work good but its really erratic at idle so I have some other issues to track down thanks for the help

[1bad79]

I worked on my car some tonight again I had some erratic timing so I pulled the chinesium distributor and installed the best gm one I had that took care of a lot of the issues but it still idles like complete crap.  I tried multiple things even manifold vacuum to the vacuum can this seems to be the most effective thing I did but now it wouldn't idle below a 1000 even with the plates shut all the way but it was smother so I re read the part in cliffs book about the idle circuit and think I discovered an issue with the carb I thought the upper air bleeds were in the air horn and just below were the lowers but I think I was mistaken and believe I have 2 sets of upper air bleeds one next to the tapered screw and one just below in the carb body, does this carb have the wrong air horn? or am I just wrong on what the function of those holes are I have a pic but I guess its to big as I cant post it thanks steve

[Cliff Ruggles]

The 17058253 has two pairs of main air bleeds.

The upper idle air bleeds are just above the DCR's, the second pair in the main casting just above the transfer slots.

Those are excellent carburetors.  Sounds like yours just needs a bit more idle fuel to the mixture screws for that engine/cam combination.....Cliff

[1bad79]

Thanks for the quick reply I will try to add some fuel then thanks steve

[1bad79]

I went to .054 on the down channel restriction and .095 on the mix screws vacuum steadied out a lot but still to fast with the plates shut im thinking about resizing the bypass air slightly smaller,not sure if going to get back to it this week, busy at work so if there are any other ideas feel free to post  thanks steve

[1bad79]

I got to work with it some tonight I went back to timing I set it at 12 degrees and went back to ported vacuum played with the mix screws and got it idling pretty well.I have different plugs coming I'm sure the heat range is to high. I noticed a off idle kinda chug or stumble until about 1700 rpms but that might be the plugs but I still have a wildly fluctuating vacuum gauge so I pulled the plugs and used my leak down detector to check all the cylinders thinking the valves might be hanging open but I found all cylinders had no dectable leak so after I get the new plugs I'm going to try a different gauge and re check of vacuum leaks

[1bad79]

so I have tried everything  I can timing wise no vac leaks seems good off idle and up but wont idle for crap. ive got a few holleys around im going to try one out and see if it makes a difference thanks for the help steve