Go Back   The Ford Barn > General Discussion > Late V8 (1954+)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 08-24-2017, 08:45 AM   #1
nstegall
Member
 
Join Date: May 2011
Posts: 94
Default Heavy Black Smut on Plugs

I have a 1986 V8 Buick with a new remanufactured four barrel carb. It ran great for about month and then the plugs had heavy black smut on them. It continue to do the sam about every two or three hundred miles with new plugs. I have not done anything to the carb. I only get around 8 to 9 miles per gallon. Everyone here has different opions, but none seems to fit. Looking for suggestion on what to do to resolve this issue.

Many thanks,
Neil
nstegall is offline   Reply With Quote
Old 08-24-2017, 08:48 AM   #2
Ole Don
Senior Member
 
Ole Don's Avatar
 
Join Date: May 2010
Location: St. Michael, Minnesota
Posts: 1,713
Default Re: Heavy Black Smut on Plugs

Remove the carb, and take it to a reputable carb man. You may need to ship it to find a real pro, carbs are getting rare. If the carb gets repaired correctly, your new plugs should clean up after a few miles.
Ole Don is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 08-24-2017, 10:41 AM   #3
nstegall
Member
 
Join Date: May 2011
Posts: 94
Default Re: Heavy Black Smut on Plugs

Don,

Thanks, but this carb is a reman about four months old. Does not need rebuilding.
nstegall is offline   Reply With Quote
Old 08-24-2017, 11:16 AM   #4
frank long island
Senior Member
 
frank long island's Avatar
 
Join Date: May 2010
Location: westbury ny
Posts: 854
Default Re: Heavy Black Smut on Plugs

I agree with don rebuilt ,that doesn't mean anything these days you get new parts that are defective as stated take it to a reputable builder something is wrong with the carb I bet it wouldn't pass emissions test may have been rebuilt with parts that are not compatible with the fuels of today, just my 2 cents worth
frank long island is offline   Reply With Quote
Old 08-24-2017, 12:11 PM   #5
scicala
Senior Member
 
scicala's Avatar
 
Join Date: Jun 2010
Location: Detroit suburb, MI
Posts: 3,697
Default Re: Heavy Black Smut on Plugs

You said the carb doesn't need to be looked at because it was just rebuilt. Name something else that's more likely to cause the problem besides a carb issue ?
I would start with the carb regardless of who rebuilt it. Stuff does happen. My first guess would be a soggy float.

Sal
scicala is offline   Reply With Quote
Old 08-24-2017, 12:20 PM   #6
dmsfrr
Senior Member
 
dmsfrr's Avatar
 
Join Date: Aug 2012
Location: Abq, NM
Posts: 3,598
Default Re: Heavy Black Smut on Plugs

Sponsored Links (Register now to hide all advertisements)
There's probably lots of black soot on the inside ends of the tailpipes too.
I agree with Don, Frank and Sal. Something is wrong with the carb, no matter how new it is.
The bad mileage and all that black soot is from way too much fuel going thru the carb & engine.
You didn't mention the car using oil or blue-ish smoke out of the exhaust so it's not likely to be oil.
(and the plugs would be wet from the oil)

If the place you got the carb will do an exchange you might be out less dollars, but you could end up with another like the bad one you've got. Hopefully it's not an example of their normal quality of work.
Quote:
Originally Posted by frank long island View Post
.... may have been rebuilt with parts that are not compatible with the fuels of today...
Any internal part not compatible with ethanol could be ruined. Starting with the: float valve(s), floats, diaphragms... etc. etc.

.

Last edited by dmsfrr; 08-30-2017 at 11:06 AM.
dmsfrr is offline   Reply With Quote
Old 08-24-2017, 07:01 PM   #7
JeffB2
Senior Member
 
JeffB2's Avatar
 
Join Date: May 2010
Location: Phoenix,AZ
Posts: 1,417
Default Re: Heavy Black Smut on Plugs

On many of the forums guys are quick to blame the Carb and then the real culprit turns out to be excessive fuel pressure caused by fuel pumps that are off shore produced and are producing pressures well over specs. This is something many do not bother to check,find out what your specs should be and then run a test this video may help show you what is involved. https://www.youtube.com/watch?v=maPgobDE_1E
JeffB2 is offline   Reply With Quote
Old 08-24-2017, 07:28 PM   #8
dmsfrr
Senior Member
 
dmsfrr's Avatar
 
Join Date: Aug 2012
Location: Abq, NM
Posts: 3,598
Default Re: Heavy Black Smut on Plugs

Quote:
Originally Posted by JeffB2 View Post
On many of the forums guys are quick to blame the Carb and then the real culprit turns out to be excessive fuel pressure caused by fuel pumps that are off shore produced and are producing pressures well over specs. .....
True enough. nstegall didn't say anything about changing the fuel pump, so the assumption is he has the same one as when it was working fine, and before that. Since the carb was most recently changed before the problem happened, it may(?) be more likely the culprit.
And yes, double checking the fuel pressure while you're under the hood already is a good thing, even before doing something with the carb, to help narrow down where the problem really is.
The car may have a defective or missing fuel filter and there's crud stuck in the carb float valve...
.

Last edited by dmsfrr; 08-30-2017 at 11:04 AM.
dmsfrr is offline   Reply With Quote
Old 08-24-2017, 11:35 PM   #9
scicala
Senior Member
 
scicala's Avatar
 
Join Date: Jun 2010
Location: Detroit suburb, MI
Posts: 3,697
Default Re: Heavy Black Smut on Plugs

Also, assuming your Buick has an original type carburetor, it's not uncommon for Quadrajet floats to absorb fuel and cause a higher fuel level.

Sal
scicala is offline   Reply With Quote
Old 08-30-2017, 08:44 AM   #10
Charlestown
Junior Member
 
Join Date: Jan 2017
Posts: 9
Default Re: Heavy Black Smut on Plugs

problem with carbon fuel deposits maybe?
Charlestown is offline   Reply With Quote
Old 08-30-2017, 08:47 PM   #11
cousinjd
Member
 
Join Date: Jan 2011
Location: Nebraska
Posts: 47
Default Re: Heavy Black Smut on Plugs

Air filter plugged?
cousinjd is offline   Reply With Quote
Old 08-30-2017, 09:59 PM   #12
Alaska Jim
Senior Member
 
Alaska Jim's Avatar
 
Join Date: May 2010
Location: Palmer, Alaska
Posts: 1,573
Default Re: Heavy Black Smut on Plugs

Sal, I have rebuilt hundred's of Q-jet carbs. the #1 cause on most of them was the stupid neopreme ( or what ever it was made of ) float. there are brass floats available for them ,but they can be finicky, but not bad. I used them when I could get them. I personally like the Q-jet carb. I think it is easy to work on, just has lots of parts. I think that is why they get a bad rap from most people. there used to be many parts available over the counter of the GM dealers to really make these thing work . you just need an assortment of metering rods and springs, etc. just like most carbs. ran one on my '75 K-20 P/u for 29 years. had to rebush the throttle shafts once and several rebuilds over the years. I also think the key to any carb. is clean filtered fuel. just my .02.----- JIm
Alaska Jim is offline   Reply With Quote
Old 08-31-2017, 10:18 AM   #13
scicala
Senior Member
 
scicala's Avatar
 
Join Date: Jun 2010
Location: Detroit suburb, MI
Posts: 3,697
Default Re: Heavy Black Smut on Plugs

Jim, I agree with what your saying. I've done 100's of Quadrajets also, along with all domestic carbs. Totally agree on the floats. I also use the brass floats to replace the soggy ones. I believe the material they are made of is called nitrophyl. Kind of like a thin hard shell over a styrofoam sponge.
I also think Q-Jets perform very well. The reason people use Holley's is because of the hot rod reputation, and they are more attractive visually.

Sal
scicala is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 10:08 AM.