1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

Stumbling on acceleration

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  #16  
Old 09-24-2018, 12:40 AM
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Originally Posted by Brnfree


I agree that’s what the book says and I wish I could make that work but FWIW I couldn’t get a clean idle with the secondaries open. Maybe it’s because the later 4180s like mine only have two idle mixture adjustment screws? I don’t know. I can say the two that I rebuilt both had the secondaries at zero when I took them apart and that’s also where I found my tuning happy place.

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The 4180, 4160, and the Autolite 4100 all only have 2 idle air mixture screws. Secondary idle air is fixed. If you can not get the engine to idle properly with the seconday's set to factory spec's the carb Idle air circuit is not suitable for the application or there are other issues with the carb.

 
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Old 09-24-2018, 04:56 AM
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The stumble or hesitation is from a stop or slow roll. Once at cruising speed, when I floor it , its a brief hesitation. Also wanted to mention that I did replace the fuel filter when I replaced the tune up items. It's the clear "in line" type and the flow when running looks fine. Like I said initially, the truck starts up immediately, runs and idles great, even has a lot of giddy-up once it catches. We'll get this old girl right.
 
  #18  
Old 09-24-2018, 11:59 AM
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after fully warm, find a deserted place, like an empty parking lot. Stomp accelerator to the floor and hold it for until top of 2nd gear. Let us know exactly what it does when you pop throttle open that hard and don't lift. Does it pop? Does it struggle gaining speed? Does it take off burning rubber and run fine when full throttle?
 
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Old 09-24-2018, 12:04 PM
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Originally Posted by Odisvan
after fully warm, find a deserted place, like an empty parking lot. Stomp accelerator to the floor and hold it for until top of 2nd gear. Let us know exactly what it does when you pop throttle open that hard and don't lift. Does it pop? Does it struggle gaining speed? Does it take off burning rubber and run fine when full throttle?
The problem is if it "pops or sneeze" up thru the carb it can blow out the power valve on older Holley's and lead to other problems.
He is best to pop off the filter lid and give a look see into the carb, motor off, to see if it squirts.
Dave - - - -
 
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Old 09-24-2018, 01:10 PM
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When its cold the throttle response is not as bad but it still has to be a timid acceleration, but it will still pop and die if I just accelerate normally like you would any other car. its a little worse when warm, just more touchy on acceleration. At this time I don't pull out in front of anyone . I need time to play with the pedal. I did look in to the carb and it sprayed pretty good when I throttled it. I'll try the parking lot, but I have a feeling its gonna pop and die. Does start right up though. Other than that, like I said before, once I get it past the stumbling, she takes off and runs perfect. Thanks again to all for helping with this issue.
 
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Old 09-24-2018, 04:50 PM
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Originally Posted by Metalleg1984
When its cold the throttle response is not as bad but it still has to be a timid acceleration, but it will still pop and die if I just accelerate normally like you would any other car. its a little worse when warm, just more touchy on acceleration. At this time I don't pull out in front of anyone . I need time to play with the pedal. I did look in to the carb and it sprayed pretty good when I throttled it. I'll try the parking lot, but I have a feeling its gonna pop and die. Does start right up though. Other than that, like I said before, once I get it past the stumbling, she takes off and runs perfect. Thanks again to all for helping with this issue.
Did it spray as soon as the throttle was moved or did the throttle move a little and then it sprayed? It should be as soon as the throttle is moved.
I don't know how the pump is set up on that carb, what model is it and is a Holley right? The Holley's I have played with you can change out the pump cam or ramp and the squirters to larger or smaller size.
I find most of the time just going to a larger squirter, 28 is stock, to a 31 is all that is needed.

I still say it is a carb issue and it runs better when cold is because the choke is on and this makes it richer to over come the lean pump shot.

BTW have you checked the timing yet? A little more advance can help but not too much you start to get pining.
Dave ----
 
  #22  
Old 09-24-2018, 05:25 PM
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Originally Posted by Metalleg1984
When its cold the throttle response is not as bad but it still has to be a timid acceleration, but it will still pop and die if I just accelerate normally like you would any other car. its a little worse when warm, just more touchy on acceleration. At this time I don't pull out in front of anyone . I need time to play with the pedal. I did look in to the carb and it sprayed pretty good when I throttled it. I'll try the parking lot, but I have a feeling its gonna pop and die. Does start right up though. Other than that, like I said before, once I get it past the stumbling, she takes off and runs perfect. Thanks again to all for helping with this issue.
Again the carb is likely due for a rebuild I suspect it has never been done in a truck that is now 30 years old generally carbs should be redone every few years. Holley's tend to get flat spots when they are due for a rebuild.
 
  #23  
Old 09-24-2018, 06:14 PM
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I agree. I think its a carb issue. When I get it taken care of, I'll update the progress. Thanks again to you all for your insight and recommendations.
 
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Old 09-29-2018, 09:03 AM
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I finally got around to removing the Holly and noticed that the stock intake is a spread bore. I thought the 351W came with a square bore. I bought a phenolic spacer for installing the new carb,but it is set up for a square bore intake. Will that work or should I order a spread bore spacer. I know there is no such thing as a dumb question, but mine sure sounds like one.
 
  #25  
Old 09-29-2018, 09:31 AM
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Also, Am I able to ditch the EGR plate and EGR valve without any issues or should I keep it in place?
Thanks in advance for any help and or suggestions.
 
  #26  
Old 09-29-2018, 08:01 PM
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What carb did you get? The stores sell square to spreadbore adapters. People frown on adapters but these seem to work ok, I have used them plenty of times before. I would use some sort of spacer or adapter in place of the EGR plate if that is the type you have. If you mount the carb up were it was with the EGR spacer, it just seems to work better and everything fits better.
 
  #27  
Old 09-30-2018, 07:18 AM
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Ditching EGR depends where you live and if inspections, I guess, as it is an emissions thing. I’ve known guys to make block off plates out of scrap steel to remove egr
Ok, anytime you lean out it’ll pop. Rich won’t pop. Your accelerator pump is likely turned to leather from old age. A pop from a hard start indicates lean. I’m sure if you back out of it quickly and lightly throttle it catches up and moves on out, albeit at a slower and more measured acceleration than you’d prefer.
 
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Old 09-30-2018, 10:04 AM
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Thanks for the advice. Oh and btw, my ignorance on thinking the intake was a spread bore. It is a square bore 4 hole. I purchased a 1406 Eddy. For now I have cleaned up the EGR plate and carb base. Also got an aluminum 1" spacer and just test fitted the carb. All linkage lines up and its a perfect fit except for the EFE valve. Just removed it and am going to look for a freeze plug to block the hole as suggested by a member of this forum. That's what it is all about. I wouldn't have thought of that..... Thanks to whoever that is. Once this is all together, I'll see how she's running. If I still have issues, my next step is to purchase a new Eddy intake (non EGR since we don't have state inspections here), then ditch the EGR plate and valve. Just trying to save another 3 to 4 hundred.
Thanks again to all. Will update on this journey.
 
  #29  
Old 10-01-2018, 09:03 AM
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Okay members.
This is what I did with the help and advice from you all:
Bought an Eddy 1406 and all necessary linkage and adapters for Ford automatic. Cleaned up EGR base plate and carb base, Installed new base gasket. Installed EGR plate. On top of that is a 1" aluminum spacer with an interchangeable square bore open or four hole insert. I opted for the four hole since my intake is that way. Installed the carb and linkage components, had to use 3" 5/16-18 bolts to mount carb, spacer and EGR plate. Couldn't locate any studs long enough locally. Hooked up all vacuum lines and fuel lines.
Grabbed fire extinguisher and cranked her up. Choke worked perfectly. Hit the throttle after a couple minutes and it idled down. Took her for a spin and it accelerates great with no hesitation at all and keeps going until I back off. I can say that this was a success. Thanks to all who chimed in.
 
  #30  
Old 10-01-2018, 05:59 PM
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Originally Posted by Metalleg1984
Okay members.
This is what I did with the help and advice from you all:
Bought an Eddy 1406 and all necessary linkage and adapters for Ford automatic. Cleaned up EGR base plate and carb base, Installed new base gasket. Installed EGR plate. On top of that is a 1" aluminum spacer with an interchangeable square bore open or four hole insert. I opted for the four hole since my intake is that way. Installed the carb and linkage components, had to use 3" 5/16-18 bolts to mount carb, spacer and EGR plate. Couldn't locate any studs long enough locally. Hooked up all vacuum lines and fuel lines.
Grabbed fire extinguisher and cranked her up. Choke worked perfectly. Hit the throttle after a couple minutes and it idled down. Took her for a spin and it accelerates great with no hesitation at all and keeps going until I back off. I can say that this was a success. Thanks to all who chimed in.
I don't like using bolts for things like carb or Tstat if they were not from the factory.
The reason is the bolts can bottom out before they tighten down.

You can use all thread rod to make carb studs.
Once you know how long you want the stud(s) thread 2 nuts on the rod and place 1 nut on either of where you need to cut the rod.
Cut the rod and where you made the cut round the end either on the grinder or hand file. After the grinder I hit it with a wire wheel also. Then run the nuts off where the cut was and cleaned up.
They should come right off, do this till you have all the studs you need.

Good to hear you got it running good again and all it took was a new carb LOL
Dave ----
 


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