Slant Six Forum :: Black smoke, rough engine, fouled plugs

: I recently rebuilt a Holley 1920 for a '73
: Valiant when I noticed that I was getting
: severe fouling of the spark plugs, rough
: running and a lot of black smoke. The severe
: fouling (dry black deposits on all plugs)
: and emission of black smoke continues even
: now after the carburetor rebuild and new
: plugs.
:
: The coil and plugs were replaced but the
: problem continued. The engine starts fine
: when cold but after warmup begins to run
: rough. After turning the engine off for
: several minutes and then restarting the
: engine is very rough until the throttle is
: opened to "clear it out". Then the
: engine runs better but still not smooth and
: still a lot of black smoke.
:
: I removed the economizer diaphram assembly and
: replaced the cover and gasket and drove the
: car. The engine seemed to run a little
: smoother. On stopping and restaring the
: engine the engine was still a little rough
: but not as bad as before. The engine seemed
: to run better but not like it should. The
: exhaust was still black. There was
: hesitation on starting from a stop light.
:
: This sounds like an overly rich condition.
: Could the "mainwell and economizer body
: assembly" that holds the main jet be
: clogged or stuck? Has anyone ever
: disassemnled one of these? (Note: this is
: not the economizer diaphram assembly held on
: by 3 screws, this is the main body that
: contains the main jet.)
:
: Any ideas on what may be causing these
: symptoms?

:
: I recently rebuilt a Holley 1920 for a '73
: Valiant when I noticed that I was getting
: severe fouling of the spark plugs, rough
: running and a lot of black smoke. The severe
: fouling (dry black deposits on all plugs)
: and emission of black smoke continues even
: now after the carburetor rebuild and new
: plugs.
:
: The coil and plugs were replaced but the
: problem continued. The engine starts fine
: when cold but after warmup begins to run
: rough. After turning the engine off for
: several minutes and then restarting the
: engine is very rough until the throttle is
: opened to "clear it out". Then the
: engine runs better but still not smooth and
: still a lot of black smoke.
:
: I removed the economizer diaphram assembly and
: replaced the cover and gasket and drove the
: car. The engine seemed to run a little
: smoother. On stopping and restaring the
: engine the engine was still a little rough
: but not as bad as before. The engine seemed
: to run better but not like it should. The
: exhaust was still black. There was
: hesitation on starting from a stop light.
:
: This sounds like an overly rich condition.
: Could the "mainwell and economizer body
: assembly" that holds the main jet be
: clogged or stuck? Has anyone ever
: disassemnled one of these? (Note: this is
: not the economizer diaphram assembly held on
: by 3 screws, this is the main body that
: contains the main jet.)
:
: Any ideas on what may be causing these
: symptoms?

: Be sure to check the float height. If too high,
: gas will poor in the manifold and make you
: run rich. You can try lowering the float to
: see if it helps.
:
: Chuck

: Yes, I did check the float height and the fuel
: level. Both were OK. The engine is running
: much better since I disabled the economizer
: diaphragm assembly. I think the problem is
: the economizer body may be clogged
: internally.

: I had some of those Holley foam filled floats
: get a nick or crack in their outer skin,
: then soak up fuel and get heavy. Did you get
: a new float in the rebuild kit?
: DD

Author:	John Richards [ Sat Jun 01, 2002 1:46 pm ]
Post subject:	Black smoke, rough engine, fouled plugs
I recently rebuilt a Holley 1920 for a '73 Valiant when I noticed that I was getting severe fouling of the spark plugs, rough running and a lot of black smoke. The severe fouling (dry black deposits on all plugs) and emission of black smoke continues even now after the carburetor rebuild and new plugs. The coil and plugs were replaced but the problem continued. The engine starts fine when cold but after warmup begins to run rough. After turning the engine off for several minutes and then restarting the engine is very rough until the throttle is opened to "clear it out". Then the engine runs better but still not smooth and still a lot of black smoke. I removed the economizer diaphram assembly and replaced the cover and gasket and drove the car. The engine seemed to run a little smoother. On stopping and restaring the engine the engine was still a little rough but not as bad as before. The engine seemed to run better but not like it should. The exhaust was still black. There was hesitation on starting from a stop light. This sounds like an overly rich condition. Could the "mainwell and economizer body assembly" that holds the main jet be clogged or stuck? Has anyone ever disassemnled one of these? (Note: this is not the economizer diaphram assembly held on by 3 screws, this is the main body that contains the main jet.) Any ideas on what may be causing these symptoms? 1851n@lycos.com

Author:	Doctor Dodge (Doug Dutra) [ Sun Jun 02, 2002 7:54 am ]
Post subject:	Re: Black smoke, rough engine, fouled plugs
Quote: : I recently rebuilt a Holley 1920 for a '73 : Valiant when I noticed that I was getting : severe fouling of the spark plugs, rough : running and a lot of black smoke. The severe : fouling (dry black deposits on all plugs) : and emission of black smoke continues even : now after the carburetor rebuild and new : plugs. : : The coil and plugs were replaced but the : problem continued. The engine starts fine : when cold but after warmup begins to run : rough. After turning the engine off for : several minutes and then restarting the : engine is very rough until the throttle is : opened to "clear it out". Then the : engine runs better but still not smooth and : still a lot of black smoke. : : I removed the economizer diaphram assembly and : replaced the cover and gasket and drove the : car. The engine seemed to run a little : smoother. On stopping and restaring the : engine the engine was still a little rough : but not as bad as before. The engine seemed : to run better but not like it should. The : exhaust was still black. There was : hesitation on starting from a stop light. : : This sounds like an overly rich condition. : Could the "mainwell and economizer body : assembly" that holds the main jet be : clogged or stuck? Has anyone ever : disassemnled one of these? (Note: this is : not the economizer diaphram assembly held on : by 3 screws, this is the main body that : contains the main jet.) : : Any ideas on what may be causing these : symptoms? One "long-shot" to check is a failed fuel pump diaphram. I had a car give me these bad carb. symptoms when the problem was the fuel pump pouring gas into the crankcase and the pcv system pulling-in the vapors when hot. It all "clicked" when I saw the oil level had risen on the dipstick. More likly is your thought that the 1920's main metering block is "shot". These are sealed units and very difficult to service. The best you can do is spray in carb. cleaner and blow campressed air through them every which-way. It sounds like it is time to fine and try another carb. I have had many Holley 1920 work great for years and then pick-up some werid problem, I rebuild the carb. and can not fix it, get fed-up and replace the unit to get back to good performance. (That's why I tend to run more Carters, I have better luck successfully rebuilding them) DD

Author:	Chuck Rivers [ Mon Jun 03, 2002 1:43 pm ]
Post subject:	Re: Black smoke, rough engine, fouled plugs
Be sure to check the float height. If too high, gas will poor in the manifold and make you run rich. You can try lowering the float to see if it helps. Chuck Quote: : : I recently rebuilt a Holley 1920 for a '73 : Valiant when I noticed that I was getting : severe fouling of the spark plugs, rough : running and a lot of black smoke. The severe : fouling (dry black deposits on all plugs) : and emission of black smoke continues even : now after the carburetor rebuild and new : plugs. : : The coil and plugs were replaced but the : problem continued. The engine starts fine : when cold but after warmup begins to run : rough. After turning the engine off for : several minutes and then restarting the : engine is very rough until the throttle is : opened to "clear it out". Then the : engine runs better but still not smooth and : still a lot of black smoke. : : I removed the economizer diaphram assembly and : replaced the cover and gasket and drove the : car. The engine seemed to run a little : smoother. On stopping and restaring the : engine the engine was still a little rough : but not as bad as before. The engine seemed : to run better but not like it should. The : exhaust was still black. There was : hesitation on starting from a stop light. : : This sounds like an overly rich condition. : Could the "mainwell and economizer body : assembly" that holds the main jet be : clogged or stuck? Has anyone ever : disassemnled one of these? (Note: this is : not the economizer diaphram assembly held on : by 3 screws, this is the main body that : contains the main jet.) : : Any ideas on what may be causing these : symptoms? webmaster@omnipages.com

Author:	John Richards [ Mon Jun 03, 2002 5:40 pm ]
Post subject:	Re: Black smoke, rough engine, fouled plugs
Quote: : Be sure to check the float height. If too high, : gas will poor in the manifold and make you : run rich. You can try lowering the float to : see if it helps. : : Chuck Yes, I did check the float height and the fuel level. Both were OK. The engine is running much better since I disabled the economizer diaphragm assembly. I think the problem is the economizer body may be clogged internally.

Author:	Doctor Dodge (Doug Dutra) [ Mon Jun 03, 2002 10:48 pm ]
Post subject:	Re: Black smoke, rough engine, fouled plugs
Quote: : Yes, I did check the float height and the fuel : level. Both were OK. The engine is running : much better since I disabled the economizer : diaphragm assembly. I think the problem is : the economizer body may be clogged : internally. I had some of those Holley foam filled floats get a nick or crack in their outer skin, then soak up fuel and get heavy. Did you get a new float in the rebuild kit? DD

Slant Six Forum https://www.slantsix.org/forum/

Black smoke, rough engine, fouled plugs https://www.slantsix.org/forum/viewtopic.php?t=3701	Page 1 of 1

Author:	John Richards [ Thu Jun 06, 2002 12:45 am ]
Post subject:	Re: Black smoke, rough engine, fouled plugs
Quote: : I had some of those Holley foam filled floats : get a nick or crack in their outer skin, : then soak up fuel and get heavy. Did you get : a new float in the rebuild kit? : DD Yes, I bought a new float because the old one was showing the sort of decomposition you referred to.

Page 1 of 1	All times are UTC-07:00
Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/