QuickFuel 880 Surging/Missing At Wide Open Throttle

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3yearcuda

3yearcuda

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Alberta, Canada
Hello All. I bought the Quickfuel SS-880-VS to replace the Holley 770 and put it on my bored 30 over 440 with Eddy dual plane, headers, stock heads, RV purple cam, not sure of lift/duration but its not overly aggressive. Fuel/Air at 11, initial timing at 16 deg. 5-6 psi fuel pressure. 3.73 gears with 727 Auto with shift kit and 2700 stall. I am running a Mopar Electronic ignition and orange box that's only 2 years old. This is in a 69 Barracuda notch. The carb came with primary 80, secondary 86 and power valve 6.5. I am in Alberta Canada at 3000 ft above sea level. Initially, out of the box the engine started and idled fine but when I was driving it and went to punch it, it would die and flood out. The speedshop that sold it to me supplied me with 78's and 84's so I put the 78 in prim and 84 in secondary. After doing this it would barely start and would backfire through the exhaust. Very loud bang. Thinking a lean condition, I put the primary back to 80 and kept secondary at 84. Started fine, idled well while driving and at WOT it pulled hard but seemed to be missing/surging slightly on the way up to WOT. Thinking a little lean on the secondary side I put the 85's in the secondary but now seems very sluggish. Now I'm not sure which way to go from here. I swapped out the Champ RJ12YC's and put on new MSD wires as they were needed and hoping if an ignition thing it would clear up. I wondered about the power valve but when talking to Quickfuel they said they just change when it opens , not how much it flows. They said that the power valve channel restrictions would need to be changed to larger size to increase the fuel flow. Really?.......Do I have to go to all this with a new carb?
If anyone has dealt with surging/missing at WOT and found a fix, I would love to hear your story so I can give it a try. Appreciate the help.
 
Curious as to where your total timing falls and when it's all in by. I see 16 initial if it's over advancing it could be what's causing your issue. Also are you running a vacuum advance. The vacuum shouldn't be a factor at wot, just trying to pull a little more info. Have you looked at the plugs? I would personally start on the ignition side then go to fuel delivery. What kind of rpm are you looking at when this occurs? There's some history with the orange boxes scattering spark at higher rpm as well as issues with rotor phasing with the Mopar distributors. Did you have this issue before the carb swap? Keep in mind most carbs are setup to cover a wide array of applications but don't always work well on any particular application.
 
I will find total timing out tonight. Been meaning too but just haven't yet. I am running vacuum advance from the dist to the carb. The plugs I pulled where hard to read as they were pretty black for the initial rich jets. I did put 4 new ones into holes that were easy to get at and after a bit of a run they were lighter than the usual light brown I have been used to with previous carbs. The missing starts as soon as I put my foot down but don't notice it when cruising at 2500 rpm. I never noticed any issue when I had the 780 Holley. It was great on the top end with no miss, but always sluggish off the hop. I swapped the holley for a Demon 750 all mechanical but wouldn't pull like the Holley vacuum secondary carb did. I did notice some surging at highway speeds with the Demon but from a start to WOT situation, I never noticed surging/missing like I do now. This 880 QF electric choke, vacuum secondary pulls like a freight train from stop to WOT except for this miss/surging thing.From a stop and hammer on it, I would say it becomes noticeable at about 3500-3600rpm and cleans up just before it shifts at 5500rpm. Maybe its time to swap out the ol' Mopar Distributor and box. Sure hate to spend that kind of cash though,as a MSD Ready to Run seems to be the preferred choice.
I will determine total timing tonight and see what I can see from the new plugs I have put in after a run at hiway speed for a bit. Then report back. Thanks for the help.
 
One other quick thought, you may want to check your reluctor to pick up air gap, .008".
 
IMHO, the fact that the engine ran well with the Holley at the top end with WOT says that the ignition is adequate. It maybe could be better and fire a wider range of fuel mixtures, but it obviously can work.

The smaller jets make some sense with a higher altitude. The backfire upon starting and the barely running says that something else was wrong besides the jets. The backfiring from the exhaust is due to excess raw fuel in the exhaust; the jet change would not do that as the main jets aren't in the pix when just simply starting the car. So I'd go back to the leaner jets and figure out what was wrong: a leaky base gasket, or something else is going wrong when you re-assemble the carb and causing problems IMHO.
 
I went back to the leaner 84's in the secondary and kept the 80's in the primary side. I went for a ride and it really cleaned up on the top end but still surging from part throttle to WOT. I came back home and being by myself, I screwed the idle screw in to walk the idle up to 2000 rpm, put the timing light on and got 38 degrees. I then went to about 3400 rpm and got 44 degrees. I shut it down after that as I really didn't want to have it screaming any longer, any higher, to see where it would drop off. Being that high though, doesn't it mean that there is likely too much advance? I popped the hose off the vacuum canister on the MP distributor and used the 3/32 allan wrench to turn the vacuum advance to the right 1/2 turn to lessen the advance. I then used the vac gauge to recheck the idle mixture screws in all four corners, bringing them each in until noticing the needle drop a bit then backing out until the gauge reading was at its highest on all 4 corners. One thing I have been noticing is that the vac guage reading flutters between 11 and 10 in-HG. Everything I read indicates bad plug, bad wire, or plugs not gapped enough but I gapped them all at 35 and am pretty confident that the plugs and wires are all good. I didn't get a chance to take it out the other night to see if my vacuum advance adjustment made any difference (Page 5, #8 http://www.dippy.org/upgrade/ignition.pdf), but before I do, i'll also check for the .008" air gap, and then post my results tomorrow. Thanks.
 
Definitely sounds like too much advance. But even at 3400 the vacuum advance could still be pulling advance if it's connected. When checking base or mechanical advance the vacuum needs to be disconnected and plugged off. I'd shoot for about 34 degrees total with mech and initial. Here's a good thread on the vacuum advance. The Allen screw is for setting how much timing the vacuum can adds at part throttle operation. The limiter jimjimjimmy posted makes setting the total without vacuum easier.

how to adjust vacuum advance
 
Since I posted last and prior to going for a drive, I plugged my vacuum line from the carb, capped the carb, dialed my light to 34 degrees, brought my RPM's up to 3000 and only had to turn the MP distributor a bit to get it on mark. Idled back down and my initial timing was virtually where I had it at 16 degrees. Plugged it all back in, upped my idle to 850 and went around the mixture screws and tweaked them according to the vacuum gauge. I turned the vacuum advance back to where it was after reading that it will really only help when at part throttle. I idled down to 800 rpm and went for a spin. It idles and runs very well except for the surging at mid all the way up to WOT. While out and about I tried the allen wrench to the vacuum advance 1/2 turn in but didn't find any difference so I set it back. Low on gas I headed for the house.
After reading again "nm9stheham" reply, I am wondering if when I changed the jets the first time if I didn't put it together properly and maybe the float stuck or something, so decided to go to one size smaller jet in the primary to 79's instead of the factory 80's. Secondary still at 84's. I also checked my reluctor to pick up air gap, and found it at .016" instead of the .008" it asks for, so I adjusted that. I'm beginning to wonder if my ignition system isn't just fine and maybe it is a carb issue.
I then ran out of daylight and almost out of gas, so tonight I'll head for a rip, get some gas and see if between the tighter gap and the one size smaller jet up front, makes a difference to my surging mid to WOT issue. I'll get to the bottom of this yet, and if nothing else....I'm learning a ton about my ignition system and carb. Thanks again for everyone's help.
 
Went for a rip last night with the 79's in the primary's, and found that it cleaned up quite a bit, So I went back to the 78's that I had issue with the first go around and fully expected it to be hard starting and backfire through the exhaust again. It didn't and fired right up, idled fine and actually is the best its ever been with only a slight miss/surge while driving at 3000 rpm and WOT.
I'm thinking that my issue this whole time has been carb related and have managed to fine tune my ignition but I don't think it has been the issue. When I removed the stock jets (80's primary, 86's secondary) and put in the 78's and 84's I must have done something wrong when putting the primary side back together.
Question is now........do I go even a little leaner on the primary's to a 77 jet?
Also, maybe this line of questioning is more suited for the Fuel and Air forum?
 
Nevermind, I see I'm in the Fuel And Air Forum. Thought I was clogging up the Electrical and ignition forum with my carb issue, lol.
 
There ya go.... progress! 2nd time is a charm. I have to wonder if the slight miss/surge at 3000/WOT is the secondaries opening... which I assume meams you had this miss/surge while at WOT and accelerating through 3000 RPM. You could block the secondaries closed and try again; if the miss/surge is gone, then you can focus on the secondary transition. If not, then my next thought would be the variable air restrictions into the main emulsion tubes in the primaries.

Following the Holley recommendation of 1 jet size reduction for each 2000' of altitude, it seems like you are about right in the jets now. Without plug reading (getting harder to do well IMHO with the modern pump fuels) or a wideband sensor in the exhaust, you'd need to do timed runs in consistent temp and humidity conditions on the exact same course (called a 'drag strip' IIRC) to look for best times. Since you have gone from waay rich to OK, I personally would put in a sensor and use that, or leave the primaries alone and work on other issues.

You're just scratching the surface of tuning this Quick Fuel carb, ya know LOL
 
After a few cruises, lowering my primary floats a bit, ensuring my timing is on with 38 Total/17-18 at idle, and setting the idle mix at all for corners and a fuel/air mix of 11hg, it seems the surging is happening under hard excelleration mid way through the powerband and not so much now under gradual excelleration or at WOT. Cruising at 3000 rpm I can feel it surging and the tach is jumping around a bit.
Wondering about a leaner main jet in the primary, so 77?
Maybe it's a distributor or orange box module issue as it seems to be happening when vacuum is introduced.
Or do I go mucking around with variable air restrictor jets?
Kinds stumped. The carb works really well and pulls hard but gotta get this surging cleared up.
 
So it sounds like surging under 2 separate sets of conditions? Is that correct? Then you will potentially haveto solve for 2 separate symptoms.

With hard acceleration, it would not seem that any vacuum advance would be in the picture. Easy to put a vacuum gauge on that line and see, or plug it off an test. I'd change the jet(s) and see if that changes the hard acceleration situation.

If it is surging at cruise, then that particular issue can well be in the idle circuit, which is feeding part of your fuel in cruise conditions. That involves the idle fuel restriction and idle air bleed.
 
Yes, I suppose it is two separate conditions. When cruising at say 40mph and step on it, it surges and jerks like its missing, or too rich/lean.
The second scenario is at a constant highway speed (70mph) I can feel it surging/hesitating, just not running smoothly. Like its too rich/lean or missing. The reason I don't think its ignition is due to the fact that it starts well, no missing at idle or at that 40mph, and at WOT it seems to clean up quite a bit. The weather hasn't been the best here the last few days so haven't had a chance to get out. I did buy 10ft of vacuum line so I can have my Vac gauge in the car with me to see what is going on when its doing its thing. I also have a set of 77's jets for the primaries that will be here Friday that i'll try in case it is still a little rich on the primary. My plugs are new and although have had a few miles on them I cant really tell yet by the color if they're rich or lean.
I'll post back with my results.
 
Sounds like lowering the floats helped some. I would do it a bit more and evaluate your 2 symptom cases separately; it is just for analysis on which way to go BTW, not necessarily to leave the floats low. (Of course, of the lower floats causes another symptom set that is separate, ignore that for the moment if possible. Sometimes changing floats changes so much it is hard to tell where things are going.)
 
Well....I tried 77's in the primary, left the 84's in the secondaries and found it really lean. Plugs where pretty white. So, went with one size smaller than stock with 79's in prim and 85's in secondary. Found this rich, strong fuel smell, and didn't get rid of my surging issue. I put the 78's and 84's back in for the recommended elevation, set the idle mix screws with the vacuum gauge and have now turned my attention away from the carb and timing as I have spent a lot of time testing and playing with those two areas and believe they are ok.
With that said, I think I should be looking at either a fuel supply issue or spark issue, as this surging/missing is only under load. Worse under load at lower speeds but a bit better but still there at WOT. I have checked by .008 gap in the 4 year old Summit bought Mopar Performance electronic ignition distributor, changed cap and rotor, new plugs and MSD wires, new MSD Blaster Coil. The only thing left I can think of is to try a new chrome Electronic Control Module (isn't even the dreaded Orange box) and ballast resistor.

My fuel sits at a constant 5psi when engine started but seems to drop to zero after when running for a bit. Must be a gauge issue or piece of crap getting into the gauge and blocking it off as it still runs ok at idle and when cruising down the street. I have two of the 3/8" hose with clamp style canister filters that you can buy anywhere, one before the Holley Red electric pump and one just about a foot before the 880 QF carb on 3/8 line throughout.

Not really sure where to go next......but guess I better get that fuel pressure to show a constant 5 psi, first and foremost. I'll swap out the old filters with two new ones and likely buy a new pressure gauge.

Anybody have any suggestions, thoughts, ideas or opinions?

Thanks.
 
I know it'been a few months, but any resoloution?
Chasing this issue myself.
Cranked it in the dark and seeing spark around a couple plugs. (NGK FR5's, also different carb, Edelbrock Thunder 800cfm)
 
I went through a situation like this with a quick fuel 450 dp carb. No matter what I did to the idle feed restrictions or the idle air bleeds (im using a wide band) just rite off idle into transition it would go off scale (16.5-17.8) lean until you got past it or low enough vacum to trip the power valve then would fatten up & be ok. Until the throttle went rite off idle again (cruise) sent it back & going to re bush throttle shafts on my afb & be done!
 
The only time I've experienced a surge at cruise (2500-3000 rpms) was when the rear butterflies were opened to much with the idle adjustment screw. On my QF 750 there is a screw for secondairy idle adjustment on the passengers side. If yours has it try backing it out 1/2 turn and readjust your idle and drive it again.
 
KnuckleDuster said:
I know it'been a few months, but any resoloution?
Chasing this issue myself.
Cranked it in the dark and seeing spark around a couple plugs. (NGK FR5's, also different carb, Edelbrock Thunder 800cfm)
Click to expand...

Hello. No I wasn't able to get rid of it. Will have to try again in the spring as the ol' dog is parked for the winter now. Frustrating as hell though, but if one thing has been gained is my knowledge of that carb and knowing my way around it. I haven't fired it up in the dark and looked for spark, so I guess that's an idea. Didn't think I would need to with new plugs, wires, cap, coil, etc, etc, etc, but ya never know. I will also pay attention to those back butterflies also. I'm will to try anything as I'm really running outta ideas.
 
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