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persistent spark plug fouling

 
Old 12-16-2018, 10:13 PM
  #21  
A8skyhawk
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In addition to the above - possibly a blown power valve? Ignition coil going bad would also be something Iíd check. Good luck.
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Old 12-16-2018, 10:32 PM
  #22  
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I would think it's the carb also,I just got done rebuilding a 650 Holley for my sons 84 chevy pickup. We installed it the other day and it ran good but it started loading up at an idle .We took it off today and I found the rear float valve was bad ,all brand new out of a kit.I just happen to have an extra from a different kit.I guess what I'm getting at don't think that because something is new it's good.I would check the carb.Try turning the idle mixture screws in and out and see if it makes any difference if it doesn't the float is stuck down and the fuel is just poring into the carb.
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Old 12-17-2018, 06:27 AM
  #23  
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Also, I don't think Edelbrock needle and seat can handle that much fuel pressure. And it might seem okay at idle. The fuel pump doesn't make as much pressure at low RPMs.

Last edited by derekderek; 12-17-2018 at 06:28 AM.
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Old 12-17-2018, 07:13 AM
  #24  
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Originally Posted by Japery View Post
I dont see any oil. some seem dry and others are wet with fuel. black smoke out of side pipes but not to bad
If this is the case you may have electrical issues...... Some cylinders are getting fired (dry) while others (wet) are not. Switch a couple of plug wires (run the motor) and see if the dry and wet plugs show up in different cylinders.... You may have some bad wires which may be broken internally or possibly at one of the boots. It could also be an issue with the contacts in the dist. cap (but this won't change which cylinders get fouled). If it were a bad coil all the cylinders would most likley be fouled. It's been my experience that sometimes your suspected fuel problems turn out to be electrical. Also, if you have access to a known "good running" carb (a friend's), switch with the one you have and see if it solves your problem. Good Luck.
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Old 12-17-2018, 08:10 AM
  #25  
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Youre overpressuring your carb, get the regulator and run it at 4 psi. I had the same thing goiing on with mine. IF you start it and look down the throat you may see fuel flowing through the throat. You can just crank it over and watch as well. Start there, If yo want to tear apart your carb and check the float levels as well, that could be a good idea too. All these things are assembled on a line by people who could care less if its put together correctly. I worked at a firearms factory and they could care less if the gun actually worked as inteded as long as they met their quota.
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Old 12-17-2018, 05:00 PM
  #26  
pauldana
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post better pictures of your plugs....All of them..

including threads and washer seal..


And, are you burning any oil?

Did you put the intake on yourself?

Also post a very good picture of your intake plenum with carb off..

Last edited by pauldana; 12-17-2018 at 05:12 PM.
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Old 12-17-2018, 05:57 PM
  #27  
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i did put the intake on myself and im not burning oil(not that i would know because i only drive it for 30 min at a time then change the plugs).Ill try to get pics as soon as i can
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Old 12-17-2018, 05:59 PM
  #28  
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Just want to thank everyone for there input. I do love this forum!
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Old 12-17-2018, 06:03 PM
  #29  
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Originally Posted by Japery View Post
i did put the intake on myself and im not burning oil(not that i would know because i only drive it for 30 min at a time then change the plugs).Ill try to get pics as soon as i can

If you put on the intake I would be willing to bet that youíre sucking oil through the valley and that is doing what you see thatís the reason I ask for better pictures of your plugs
and if youíre burning oil
also a picture of the plenum
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Old 12-17-2018, 06:15 PM
  #30  
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i am confused.
the engine was tuned on a dyno?
so what changed when put in car?
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Old 12-17-2018, 06:20 PM
  #31  
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Originally Posted by pauldana View Post



If you put on the intake I would be willing to bet that youíre sucking oil through the valley and that is doing what you see thatís the reason I ask for better pictures of your plugs
and if youíre burning oil
also a picture of the plenum
O.P. said its not burning oil and black smoke out the exhaust.

Last edited by HeadsU.P.; 12-17-2018 at 06:21 PM.
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Old 12-17-2018, 06:25 PM
  #32  
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Blueprint dynos all there engines before they ship them. I bought the lower end of the engine then bought a new intake,carb,dist,wires and mechanical fuel pump.
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Old 12-17-2018, 06:27 PM
  #33  
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what are the signs of oil sucking through the valley? ( wow that didnt sound good)
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Old 12-17-2018, 06:34 PM
  #34  
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Originally Posted by Japery View Post
what are the signs of oil sucking through the valley? ( wow that didnt sound good)
Depending how bad. I saw a rebuilt 57 that ran okay and smoked like a battleship. Quart in 200 miles
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Old 12-17-2018, 07:05 PM
  #35  
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im thinking 1.Check choke adjustment 2.Check the float 3.check fuel pressure. Where would the fuel be dripping from in the carb?
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Old 12-17-2018, 07:06 PM
  #36  
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Originally Posted by Japery View Post
i did put the intake on myself and im not burning oil(not that i would know because i only drive it for 30 min at a time then change the plugs).Ill try to get pics as soon as i can


Originally Posted by HeadsU.P. View Post
O.P. said its not burning oil and black smoke out the exhaust.
read above.... also black smoke will come from oil burn as well.. how do I know.... been there done that...*



Originally Posted by calwldlife View Post
i am confused.
the engine was tuned on a dyno?
so what changed when put in car?
The OP installed the intake...*

Originally Posted by Japery View Post
what are the signs of oil sucking through the valley? ( wow that didnt sound good)
Black pugs... wet oil ANYWHERE on the threads, seal ring, plug tip full area... anywhere except the porcelain outside. if it is the least bit shiny, its wet.*

Originally Posted by Big2Bird View Post
Depending how bad. I saw a rebuilt 57 that ran okay and smoked like a battleship. Quart in 200 miles
yup... I burnt 1-2 quarts a tank full chasing this ****... I do have the AFR Titan plastic intake... it is flat out bitchen,,, BUT.....you have, or I did, have issues sealing until I figured out how..* this on the C3........ on the C4 we were having rocker are studs suck... they have slightly different symptoms, but very close///

do you blow smoke after an-in gear full rpm drop (6K to 2K) then sudden full throttle..

As you know we have 6 of these cars we race, and we have built about 9 engines so far, ... all this oil burning that people are writing off as ring seal or PCV or ???? are usually actually one of 2 things..
1, oil sucking from the valley.... 2 oil sucking vis rocker arm studs.*



if wet oil on just some plugs, rocker arm studs suck... wet oil on every plug, intake oil valley suck.

Look in plenum... if it is shiny and has a very very thin oily look/feel... your sucking oil.. plenum should be bone dry after gas evaporates.

*

A lot of this looks like a rich carb,,, and yes it very well could be.. easy fix, swap on a rebuilt carb from auto zone or?? problem goes away.. thats it.. problem does not go away.. its sucking oil..

Last edited by pauldana; 12-17-2018 at 07:15 PM.
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Old 12-17-2018, 07:14 PM
  #37  
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Originally Posted by Japery View Post
im thinking 1.Check choke adjustment 2.Check the float 3.check fuel pressure. Where would the fuel be dripping from in the carb?
See post 15.
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Old 12-17-2018, 09:49 PM
  #38  
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First off, I am not familiar with the details of a DUI distributor, But I have had similar symptoms you describe when I had a bad points condenser. Something is causing a weak and poor timed spark. Just my hip shot from afar.
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Old 12-17-2018, 09:55 PM
  #39  
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Originally Posted by Bullshark View Post
First off, I am not familiar with the details of a DUI distributor, But I have had similar symptoms you describe when I had a bad points condenser. Something is causing a weak and poor timed spark. Just my hip shot from afar.

the reason I do not believe it is the spark, is because he can install new plugs and it runs good, for a while until foul up...if it were spark it would run bad right off the get go,,, not wait until they are fouled black... imho



A good detailed clean pictures of all the plugs and threads and plenum, will tell a lot more of the story.

Last edited by pauldana; 12-17-2018 at 09:57 PM.
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Old 12-17-2018, 10:47 PM
  #40  
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Originally Posted by pauldana View Post
the reason I do not believe it is the spark, is because he can install new plugs and it runs good, for a while until foul up...if it were spark it would run bad right off the get go,,, not wait until they are fouled black... imho



A good detailed clean pictures of all the plugs and threads and plenum, will tell a lot more of the story.
Not necessarily, when I had that bad condenser, the scenario you just described was mine exactly. Started, ran good at idle, stumbled when trying to rev the engine leading to dark black fouled spark plugs in a short time. Just food for thought as you isolate the root cause.


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