ok mopar gods, newbie here with a odd stumble from stop - HELP!!!

[69chargeryeehaa]

Hey guys, newbie here, good forum read it all the time.  my question is on a 1969 dodge charger, has a 74 440hp from a new yorker, 727, 8 3/4 suregrip (spring type 489 case) 3.23 gears, hooker headers, electronic ign, elderbrock ch4b intake, afb competition serries 750cfm 9755s 4bbl carb, very mild cam.  so that is the specs, and heres the problem: from a stop, like at a light, if i am to start off a normal launch, just cruising acceleration, i get a stumble, or hesitation, more like a hesitation.  only at one specific pedal position-meaning is i give it a little more acceleration the power instantly comes on, a little less and it goes away but I'm hardly accelerating.  this only happens from a stop.  I'm at a total loss as to what could cause this, it's driving me crazy, I've been thru the ignition, timing is dead on.  about 6 btdc and about 36 btdc total, no ping at wot in high gear, runs awesome otherwise.  I'm thinking accelerator pump? fuel problem? any ideas?  also while I'm on this, what thermostat are you guys running and why? I'm running a 195 deg F stat, is there an issue with running a 160 deg F stat? any input from you guys greatly appreciated.

martin

[nh_mopar_fan]

accelerator pump would be my guess.

[69chargeryeehaa]

well i pulled the air cleaner off and moved the linkage and the accel pump works, but there is 3 positions on the accel pump linkage, it was on the lowest side i think, with throttle at closed, the plunger is at it's highest point, if i move the accel pump to the next setting the accel pump plunger is lower, that mean it will give more gas? which way is the highest setting for the accel pump?  i also have another question about the thermostat, the car warms up to about 210 deg F and then the stat opens and it goes quickly to 170 and then up to 195 and stays between 190-195 until the next warm up think it's a sticky thermostat? anyone else have that problem?

martin

[deathcharger71]

maybeim wrong but i think a 195 thermostat is too hot, when i got my engine built he told me not to go higher then 165 and my car runs around 180 unless its a hot day. of course i get pings above 180 so maybe thats why i was told to run a 160 thermostat  but if my car gets to 205 i shut her down, too hot for me.

[Danny Gutierrez]

well i pulled the air cleaner off and moved the linkage and the accel pump works, but there is 3 positions on the accel pump linkage, it was on the lowest side i think, with throttle at closed, the plunger is at it's highest point, if i move the accel pump to the next setting the accel pump plunger is lower, that mean it will give more gas? which way is the highest setting for the accel pump?

martin

The setting closest to the carb body gives the most gas.  Experiment with all 3 settings to see if there is any improvement.  Generally (in my experience) the second or third setting seems to work the best. 

[69chargeryeehaa]

deth charger-as far as i heard, 160 stat is perty cold, with todays crappy fuel running at 180 is a bit cold, and the combustion chamber does'nt maintain a hot enough temperature causing unburnt fuel.  i was just wondering what everyone else is doing and why.  i ran a 160 stat and i was running at 150-160 all day, but the exhaust smelt like gas, or too rich.  if you put a 160 stat u should run 155-160 all day, i would be concerned if i were running 180 with a 160 stat :-\u might have a problem with the cooling system

danny-when u say closer to the carb ???that does'nt make cents to me cause the holes go parellel to the carb.  the holes make the plunger stay in a bit, it was on the what i would think the least acell pump setting where the plunger was all the way out at idle, the two tighter holes make the plunger move in at idle position? hope u can understand my description. 

on another note, is'nt a 440 supposed to run with a 195 thermostat? napa only has the 195 as a listing.   

[Danny Gutierrez]

danny-when u say closer to the carb ???that does'nt make cents to me cause the holes go parellel to the carb.  the holes make the plunger stay in a bit, it was on the what i would think the least acell pump setting where the plunger was all the way out at idle, the two tighter holes make the plunger move in at idle position? hope u can understand my description.

Sorry I wasn't more descriptive.  What I meant was the hole closest to the plunger.  Try all three and watch the plunger.  The hole that presses the plunger down the furthest is the one that gives the most gas.  I don't have that particular kind of carb anymore but I have owned a couple in the past. 

[Chryco Psycho]

accelerator pump woul dbe my first guess but I bet if you either disconnect the vacuum advance [ I assume it is hooked to ported vacuum , little or no vacuum at idle & more with RPM ] or insert an allen wrench into the vacuum advance & turn the screw 8-10 turns counterclockwise & reset the total timing at 36* the hesitation will disappear as the engine will now have more advance at idle

[69chargeryeehaa]

thanks danny, that's what i thought.

psyco, so if i understand you correctly, timing could be that much of an issue at idle?  the car has no other drivability issues, if i rev it in netural it's fine, but in gear from a stop i have this hesitation.  if i give a bit more gas it instantly makes power, if i let off a bit it's ok too but i'm barley accelerating.  if my timing is currently set at 6 deg btdc and i have about 35-36 deg total timing then why would you suspect timing? also i have had the timing all over the place and had base set to 10 deg btdc and no difference, i was trying to get rid of a high gear wot ping which is now gone but i lost some power which i understand is expected but the car runs amazing otherwise.  so basically what i'm saying is that i've had the timing all over the place and there was not a bit of change in the off idle hesitation which is why i don't suspect timing any more and think it's a carb thing.  thoughts? i changed the accel pump setting to give more gas as per danny's suggestion but i haven't had a chance to drive the car due to the s$it&y weather up here in toronto canada i hope to have cured the problem with the accelerator pump adjustment, but no chance for a road test yet.  and as per vacuum, i have steady 13inch pds at idle, which i think is perty healthy i wish i understood the timing thing a little better as to what the mech advance does and the vacuum does, as far as i understood, the vacuum advance works to about 2500rpm and then vacuum goes away and then the mechanical advance does the rest, am i right? any explanations apprecieated

[Chryco Psycho]

the vacuum advance starts off idle & adds timing at any point where there is significant airflow through the carb , it doesn`t just stop at 3000 rpm by inserting an allen wrenck into the vacuum pot & turning it counterclockwise 8 turns you shorten the curve so you can add 6-8 * at idle & still have the same 36* total timing & not have pinging

[69chargeryeehaa]

ummm psyco, i should try that, so maybe i could just add timing with the vacuum at idle turning the screw and leave the timing where it is? or advance it just until ping goes away? the only other thing on my mind now that i think about it is i reeally don't think that timing is the cause of my hesitation, i had the timing as high as about 13 deg, the ping was bad, but the off idle stumble or hesitation was still there, that is making me think it's a carb thing.  i did adjust the accel pump to the next higher setting but havent had a chance to go for a spin yet, i should today, and see if that made a difference.  i guess i need timing tape to find out where 34-36 deg of total advance is, i did read some where on another post the measurement of that on the pulley, but i lost it, aww well, just pick up some tape

[Chryco Psycho]

just put a mark on the damper 2 3/8 " clockwise from the TDC line for 36* , I tend to agree , if the advanced timing did not affect the stumble it is probably in the carb , I have seen timing cause a stumble before though

[69chargeryeehaa]

ok guys, i took the car for a spin last night, actually a cruise. heres what i tried: i moved the accel pump to all 3 settings with no change, and i disconnected the vac advance and plugged it with no change also. to recap, i've had the timing at as high as 13 deg and no change, that damm stumble is still there. funny thing i noticed is that if i kind of agressivly accelerate off idle there is no hesitation, just on a normal launch. disconnecting the vac advance should prove it's not a timing issue, ideas? i'm leaning towards those metering springs and carb adjustments, or how it switched to the seccondaries, if only i knew more about them, i don't even know where to start? what springs? ect... ideas? damm stumble has me stumped

[73chargercali]

i just glanced over the posts and don't know if someone mentioned it but my car had the same problem and it always acted up from stops or when it was under load like going uphill with barely any speed, so i just drove it for a year without any real worries and last month i pulled the carb and the largest vacum port off the carb was unplugged the plug was rotted away and it was wide open. so i think it would be usefull to check for vacum leaks.

[BigBlockSam]

check for vacum leaks 

[Chryco Psycho]

float level could be too  low

[69chargeryeehaa]

i checked for vacuum leaks, but found none, i also checked vacuum at idle and i get about 13 inch pds, that was the first thing i checked.  good idea though.  i'm sure it's not timing with all the tests i've done, and the hesitation never changed or got any better or worse no matter where it was.  also tried all three settings for the accel pump, no change, so it has to be something in the carb.    i guess my next step would be to take the carb apart, check the float lever and someone gave me a good pointer to change the fuel filter, that i definetly will try first.  just having a hard time to find gaskets for the afb carter competition serries 9755s carb.

[Chryco Psycho]

Edelbrock carb gaskets will work & if you are careful you may not need a kit at all
worst case Standard should have a gasket kit for it