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engine bogs down
https://slantsix.org/forum/viewtopic.php?t=38382		 Page 1 of 2
Author:  bud18007 [ Tue Dec 22, 2009 5:42 pm ]
Post subject:  engine bogs down
I just rebuilt my slant six its a 1982 d-150, brand new carburetor all new parts. My problem is that when i hit the accelerator theres a 1 or 2 sec delay in it going plus it bogs down just a little until it picks up some speed. i have plugged all my vacum lines comming out my carburtor and it idls just fine. any ideas?
Author:  carpdar [ Tue Dec 22, 2009 5:57 pm ]
Post subject: 
Mine does that too to some extent.. Check your carb bolt tightness, plugs (hey u'never know), heat riser valve, and your choke at cold (closed) and hot (vertical). I'm sure if you've rebuilt your engine you know these things, but i've had issues with the choke thermastat/arm bindage for awhile now.

hope that helps a bit
Author:  Aggressive Ted [ Tue Dec 22, 2009 6:37 pm ]
Post subject: 
Bud,

If your timing is right and you don't have any vacuum leaks or a bad vacuum pod, you may want to look into your accelerator pump discharge and check it......With the engine off, pull the air filter lid and look down the carb throat and pull on the throttle. Do you see a healthy stream of gas coming out of the discharge nozzle?

If not, try the following. With out the accelerator pump discharge working it is very awkward and frustrating because the car wants to run until you put a load on it. I drilled out the discharge nozzle on mine to .035 (#65 drill) for a very healthy pump shot. However, you might try running a old guitar string (the fine solid ones, not the medium to large wrapped strings) through the hole to knock loose the blockage. You can feed it in there once the economizer body is removed. You can also run it down the low speed air bleed and the high speed air bleeds. They usually collect dirt and or carbon if your carb has been running rich or just from setting around on a shelf collecting dust. Make sure you adjust all the slop out of the accelerator pump linkage.

Hopefully this will help. :D
Author:  carpdar [ Tue Dec 22, 2009 8:26 pm ]
Post subject: 
He says he has a "brand new" carb ted, but maybe it was on the shelf for awhile and the accelerator plunger dried out? I don't know much about the different parts, but i've rebuild mine and the parts remind me of my lawnmower haha. Besides my rambling, if this is a fuel delivery issue the carb should be ruled out if its actually new..

Try turning up your fast idle Bud, and pay attention to the engine temp in relation to your hesitation. Like i said, i've had (sometimes have) the same problem with my engine and I'm on the same page to some extent.
Author:  WyoCowboy [ Thu Dec 24, 2009 11:04 am ]
Post subject:  I have the same problem
My 63 Dart with the Holley 1920 has the exact same issue. I rebuilt it a couple of months ago, and maybe I didn't clean it well enough. I do get a squirt of fuel when I move the accelerator. Let us know if you fix your problem.
Author:  powerwagonpaul [ Sat Dec 26, 2009 6:20 am ]
Post subject: 
i too have the same problem. after reading several posts and articles, and watching SSD's video from jim handy, this is the conclusion i came up with: we all need more manifold heat.
i am running MP long tube headers with no manifold heater. after a drive across town and sitting for several minutes it has no problem. the manifold has had a nice heat soak at that point. halfway home it starts to stumble again, the manifold has cooled somewhat by then. the stumble is caused by a sudden lean-rich condition :shock: . first it goes lean-the correct amount of fuel enters the manifold, some not vaporized=lean. then as you open the throttle, the increased air flow vaporizes the fuel in the manifold+the correct amount of fuel from the carb=rich. then it balances out and runs great.
if your running stock exhaust i would make sure your hear riser is working properly. as for me i have made a hot water box for the two barell manifold i am putting on. i hope it will be hot enough, if not ideal, at least it will create a consistant temp that i can tune to.
Author:  Aggressive Ted [ Sat Dec 26, 2009 10:02 am ]
Post subject: 
powerwagonpaul,
Quote:
the conclusion i came up with: we all need more manifold heat.
Since your setup is not stock, you may want to try and electric fan modification as well.

One of the benefits of going to a electric fan on the radiator is that the manifold stays much warmer since fan isn't constantly blow cold air over the intake cooling it down. My car runs so much better, especially in the winter and gets much better mileage as a result.

Take a look at the pictures of my set up by clicking on the red link below. Once the picture comes up double click on it for full screen slide show mode.

You will also see a heat deflector in the photos for keeping the carb from boiling over which also helps keep the manifold warmer in the winter and on start up.
Author:  SlantSixDan [ Sat Dec 26, 2009 10:28 am ]
Post subject: 
Electric fans are nice if you have the charging system capacity to run them and the space to fit them, but in fact the engine cooling fan has little effect on the operating temperature of the intake manifold where it matters, and it is not necessary to do any reëngineering (electric fan, etc.) to cure a stumble/hesitation that will go away when everything is in correct repair and tune. Don't get distracted with upgrades and reinvention until after you've chased down and squashed whatever bug is causing your driveability faults, or you'll wind up wasting time, money, and effort. The stumble/hesitation being discussed here may be related to manifold heat (or lack thereof), may be carburetor-related, may be due to a faulty vacuum advance unit or hose, or could be a combination of those factors and a few others. Systematic diagnosis is what is needed here — not random guesses.
Author:  powerwagonpaul [ Sat Dec 26, 2009 12:32 pm ]
Post subject: 
no electric fans for me :wink: they all seem kinda makeshift for my taste. how is your temp probe ted? stuffed into the radiator fins? or is it one that snakes into the hose under the clamp? i dont like either.
i have checked the dizzy, it starts advancing at about 9in and is fully advanced at about 14. i have alot to learn about advance curves but that seems about right. i have read and re-read anything and everything about carbs in general and this 1920 in particular, i feel the carb is right on.
i keep coming back to manifold heat as that is the missing link, i have none. after wathcing jim handy, i can picture fuel splashing on the manifold floor, only to be vaporized later with more air flow. where as with a little heat it would vaporize instantly. any engineer types out there want to chime in here? :roll:
i suggest the manifold heat riser as another "something to look at". there seems to be alot of problems with it. some have wired it open, some closed. alot seem stuck. i plan to go with a water box, ala clifford and aussiespeed.
Author:  Aggressive Ted [ Sat Dec 26, 2009 12:48 pm ]
Post subject: 
powerwagonpaul,
Quote:
no electric fans for me Wink they all seem kinda makeshift for my taste. how is your temp probe ted? stuffed into the radiator fins? or is it one that snakes into the hose under the clamp? i dont like either.
I do not like the make shift probes either. They are very tacky for my taste as well. Take a look at my photos by clicking on the red link below my name. The temperature sender screws into a plugged fitting on the radiator. I have run the system for over four years now and using all new parts that cost less than $100. The modification is super clean. It has resulted in better mileage, no more heat soak and quicker warms ups. :) For work I drive 130 miles a day and the modification sure has reduced the gas bill. :D
Author:  wjajr [ Sat Dec 26, 2009 12:57 pm ]
Post subject: 
Dose this truck have the factory air cleaner equipped with an intake air warming flapper operated by vacuum? If so, this could be an area to check for proper function that can cause drivability problems before engine is fully warmed up.

I have to agree with the air-fuel mixture camp on this one. As suggested before, accelerator pump malfunction, lack of manifold heat, improper choke adjustment, and vacuum leaks, be they from carburetor to manifold connection (check for warped base) or a vacuum can diaphragm rip, would all be at the top of my list. Chances are, there are several devices & actions not at 100%. causing your stumbling.

Second would be timing control. Are the moving parts of the centripetal governor freely moving inside of the distributor? If the governor is stuck, or sluggish this will cause problems with acceleration.
Author:  SlantSixDan [ Sat Dec 26, 2009 1:26 pm ]
Post subject: 
Quote:
i have read and re-read anything and everything about carbs in general and this 1920 in particular, i feel the carb is right on.
I don't. Carbs in proper repair and tune tend not to make driveability problems; I think you still have an issue in your carb, but before you go too far down that road you should indeed get your manifold heat squared away.
Quote:
some have wired it open, some closed
I don't recall anyone wiring the heat riser "closed" (i.e., heat-on).
Author:  WyoCowboy [ Sat Dec 26, 2009 2:01 pm ]
Post subject: 
My MHCV is not moving; I need to get the solvent to free that up and see if that will make a difference. I can move it by hand, but I haven't played with it yet to see if "open" or "closed" effects the bog.

My vacuum can appears to be working. I don't have a gauge, but when I suck on the hose, the distributor "advances". However, I still need to check for leaks throughout the entire intake system. Other than the partial accel bog, the thing runs great. Good choke, idle, step, good high speed, 20 mpg on the highway, no vapor lock.

I'll keep you posted.
Author:  SlantSixDan [ Sat Dec 26, 2009 2:12 pm ]
Post subject: 
More info on the "brand new carburetor" please. Is it new-new, or "remanufactured"?
Author:  powerwagonpaul [ Sun Dec 27, 2009 5:08 am ]
Post subject: 
dan,
maybe your right: nobody would have it wired closed. i was just trying (poorly) to make the point that, there is a wide variance of opinions on the heat riser in general and its importance. i have come to realize that manifold heat is important on a street driver. in my case i feel lack of heat is my driveabilty issue.
i have done what i can with this carb. i have learned as much as i can because there seems to no honest carb shops anymore. i have paid for nothing before. i feel the carb is good as it runs fine other than that stumble on accel. it passes smog. gets about 20mpg. i am still reading, trying to find that aha moment, that will tell me something about the carb that would solve this problem, not giving up there.
i keep coming back to manifold heat. it runs great after a little heat soak, then stumbles as the manifold cools. in my mind, i can picture fuel splashing on the manifold floor,not vaporizing. if there is any engineer types i would like to hear what they say about that lean-rich condition.
i think in MY case manifold heat is the culprit. i think it MAY be the cause in many other cases as well. again, another "something to look at"
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