1. non cc quad, slightly bigger jets etc (aka a bit more fuel)
2. vac advance dist, 65k coil, 8mm msd plugs
3.timing set to 12* initial, 34-36 total

problems:
1. 1700 idle (smooth)..at start up and when warmed up (sometimes bumps up to 2000 when warmed up on road)
2. occasional (1/3 the time) dieseling
3. will stutter/stumble when you give more than 3/4 gas pedal, but accelerates great before that, very smooth, much better than before

possible reasons?:
1. timing to high? back down to 10 initial maybe? (for all 3 problems)
2. secondaries not working properly? (the stumbling)
3. spark plugs? i am gonna replace those anyway.
4. idle mixture screws ( i dont want to mess them if i can help it)

anyone got any other suggestions?

 

factory or aftermarket carb?

 

i said quad in 1st post..sorry i mean quadrajet it was a factory ccc, but its been converted to non cc

 

Do you have or have you checked for vacuum leaks? if its deiseling the heads are too hot. have you visually checked spark plugs?

"3. will stutter/stumble when you give more than 3/4 gas pedal, but accelerates great before that, very smooth, much better than before"

"much better than before" before what?

 

no vacuum leaks that i know of..i checked everywhere i could with a propane torch when car was running to see if any gas was sucked in and no idle surge..i do have a vacuum pressure gauge, but it was 3 mos ago and i cant remember the results..as far as i remember that wasnt the issue though.

spark plugs are getting changed just in case (still trying to figure out how to get to 3 and 5) but they were a bit gunked up..tho the tips were a normal brownish color..engine idles and runs so smooth i feel like if they were actually not functioning properly it would run rough..but idk that for sure. my other thought was maybe because my evap line is blocked off right now and gas vapor is coming out the top of the carb sometimes that might cause dieseling since fuel is floatin around? i kinda wonder why we blocked it off now, its been 3-4 mos and cant remember.

before was before i had the carb rebuilt, the car ran pretty rough before i got it back..now it purrs, but mpg is pretty bad, and all the afore mentioned problems

 

dieseling is definatley a heat issue. a hot spot in the head or something. cutting the ignition should stop combustion, if it doesn't then SOMETHING is igniting the fuel. if you had a intake manifold leak at the base and it was sucking air, it would cause high idle and a lean condition in 1 or 2 cyls. this lean condition would cause a hot spot. the vac leak would cause the high idle and the heat would cause the deiseling.

the only thing that would cause high idle aside from a vac leak would be if your throttle plates were sticking open or not set properly.

 

i thought timing was a possible issue, at least its one of the options in the my shop manual in regards to dieseling. i realized the evap line that we blocked off originally went to a canister control valve which was part of everything we removed when we got rid of all the extra vacuum lines from air system etc. once i can find the proper vacuum pressure numbers, i know ive seen them on here before, i can check psi to check that off the list.

throttle blades are the same as the butterfly valves on the primaries and secondaries right? my primary blade wasnt functioning properly before even though my choke seemed to be working so my carb guy shortened the rod a tiny bit that was holding the butterfly valve..it does seem to be a little too open at cold starts..which would account for the high idle (i think) but it idles high even when the car is warmed up and valve is supposed to be wide open..sooo

 

im trying to find a thread that talks about proper vacuum pressure numbers, but am having no luck right now. anybody know?

 

18 to 22 Hg should be average for a carbed small block Chevy. keep in mind that timing affects vacuum too. timing can also cause hot spots and dieseling, but i dont see how it can cause your idle issue.

 

Are those numbers at idle for vacuum I don't know if vacuum varies at all?
Well when we were rotating the distributor one way or the other it would affect timing and idle

 

yeah those numbers are for @ idle. timing may affect you idle a bit but it shouldn't bring it up over 1000 rpm's

 

thanks for you help bro. i got a vacuum gage on it and it was reading 21 hg at idle. i did find a line on the carb that i had somehow forgot to cap, definately helped some..brought down rpms a couple hundred, and the car hasnt dieseled since..so hopefully thats taken care of. ive still gotta figure out the rpm's some more and the sputter at full throttle, though that seems to have gotten better as well. u must be right about the timing..if the car is running well, then it must not be too far advanced and i would think you could get the idle down to somewhat normal even if you got it on the maximum advance (without pinging) man i wish i had more of a clue. and im still a little worried about the evap line and how much of an effect its having

 

is the evap line just sucking air?

 

I think I figured it out. The part of the throttle that connects to the accelerator cable was sticking a little bit. I lubed it up but not helping yet. I'm trying to figure out how to loosen it some

 

can you post a pic of your throttle linkage and carb?

 

Yeah totally. Not sure I can get to it tonight but tomorrow for sure

 

the pics, 1st one is of the problem area, where the spring and throttle cable (name?) is attached, its sticking a little bit. the last pic shows the little screw on the other side which is part of something that connects to the problem side..im guessing it all connects to the throttle blade..or something lol

 

hope im not putting too many pics up, but one more

 

that is a mess. i hate OE carbs. i had an edelbrock on mine and i loved it. so simple.

what happens if you disconnect the vacuum line from that vacuum actuator on the pass side?

 

ha..yep ..im not gonna put more money into it right now because if i stay where im moving for more than a couple years ill have to sell the car, as it will never pass emissions. the carb is working great other than this little issue though, i might just need to pick up a new spring (the one under the throttle cable) if that spot has more tension it brings the throttle "thingy" back down to where it needs to be at idle..i know that thing sticking is the only issue now, its pretty obvious. i can check the vacuum line youre talking about but whats ur reasoning with that? (just curious)

 

i went and got another spring, actually had to use it and the old one together (new one wasnt an exact copy) now it idles at 800..tensions a lil high on the gas pedal, but no biggie. almost everything is working right now..just have the bogging when i push the gas all the way to the floor..i wonder if my secondaries arent opening up and therefore not getting enough air at full throttle..idk..just the 1st thing i think of

i mean the rear butterfly valve..not secondaries per se (i can never remember whether primaries are in the front or back part)

 

my reasoning with the vac actuator was to see if that might have been holding the throttle open.

in Massachusetts we don't have emissions testing on cars more than 20 yrs. old.

bogging can be caused by either a rich or lean condition. do you get any smoke out of the tail pipes when it bogs? or after it picks up.

 

hmm..i should check that on the vac actuator..i dont like the tension on the gas pedal as is right now. yeah, Philly area has terrible laws with that emissions stuff.

id have to have someone follow me to double check , but no i dont see any smoke whatsoever (that i can tell)