dirty sparkpluges
Moderator: Team
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emt-n2-69
dirty sparkpluges
i have oily black shiney deposits only on one side of the porcelin of the plug. the ing is 30 350 with 1k miles on it. the heads are doublehumps, the carb is 750 AED unit, the cam 250@ .050 560 lift, in&ex.
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bill jones
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- Posts: 2650
- Joined: Sun Sep 05, 2004 6:38 pm
- Location: salt lake city, ut
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-Have you looked at the position of the black patches on the plugs iin relation to the incoming fuel or to the exhaust valve, meaning do all the plugs exhibit the black spots in the same orientation within the chamber?
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-Not having anymore to go on than what little you've given us I'd say the idle is way too rich, not enough timing at idle, valve stem seals or intake gaskets are allowing oil, if the chambers are a mirror finish or are highly polished on the intake side of the chamber and the intake ports are real slick---the fuel will slobber in there and carbon up.
-The plugs could be too cold, the total engine temperature running too cold, no vacuum advance, extended tip plugs stick out there in the fuel and possible oil path.
-There's a lot of problems you could have but until we know more about it we're just shooting in the dark.
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-Not having anymore to go on than what little you've given us I'd say the idle is way too rich, not enough timing at idle, valve stem seals or intake gaskets are allowing oil, if the chambers are a mirror finish or are highly polished on the intake side of the chamber and the intake ports are real slick---the fuel will slobber in there and carbon up.
-The plugs could be too cold, the total engine temperature running too cold, no vacuum advance, extended tip plugs stick out there in the fuel and possible oil path.
-There's a lot of problems you could have but until we know more about it we're just shooting in the dark.
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emt-n2-69
dirty sparkpluges
the black shiney spots are on the top side of the porcerlins, on some the electrode is black shiney too. im not sure if its toward the intake or the exoust. the plugs are stock type super bosch wr9fc. the plugs have lots of oil around the threads also. the valve covers are not leaking oil down to them. the timing is 36 deg initial and total at 1300rpm no advance. the distributer is MSD with the timing mech locked. the eng temp is 195 deg. the carb has 4 corner idle screws, each are 1 turn out. with the idle scews turned in any more the eng stumbles and wants to cut off. the stem seals are rubber type that wrap around the valve stem and guide.the chambers and intake ports are ported but not polsihed. the plug porcerlins do extend above plug threads. on some of the plugs the porcerlins are black and suty. the jets are 69 , the carb came with 72s up front, any less and the car serges.
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bill jones
- Guru
- Posts: 2650
- Joined: Sun Sep 05, 2004 6:38 pm
- Location: salt lake city, ut
- Contact:
-and how are you driving the engine when they get sooted up.
-Being that they are getting sooted up means the carburetor is TOO rich and that may not have one thing to do with jets.
-If you are just putting around the idle transfer slot is the likely allowing too much fuel to the engine at part throttle.
-I don't know how cold those plugs are but I would go hotter on plugs until you get it sorted out.
-Being that they are getting sooted up means the carburetor is TOO rich and that may not have one thing to do with jets.
-If you are just putting around the idle transfer slot is the likely allowing too much fuel to the engine at part throttle.
-I don't know how cold those plugs are but I would go hotter on plugs until you get it sorted out.
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emt-n2-69
dirty sparkpluges
yes i am putting around . i haven't drove it hard yet. if it is the transition slots do you think that if i open the ported vaccum port on the side of the metering block will creat a leaning affect for the transisition circuits for mild driving. when you say hoter plug does the # increase or decrease on the plug.
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bill jones
- Guru
- Posts: 2650
- Joined: Sun Sep 05, 2004 6:38 pm
- Location: salt lake city, ut
- Contact:
-I have no idea about the heat ranges on that brand of sparkplugs.
-To fix part throttle drivability the easiest way is to use a vacuum advance and get the engine all the timing it can stand while it has vacuum.
-The fuel that feeds the transition slot comes from the idle restriction and that is usually around .036" for that size carburetor.
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-I would run the secondary idles clear in and then back them out only 1/4 turn and do all the rest of the idle mixtures using the primary screws.
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-If you can find the idle restrictions it's fairly easy to restrict the orifices with short pieces of some small diameter wire like maybe a .015" or so.
-You have to measure the orifice do the math of the square inch area and then find wire that will reduce that square inch area by say 5% or 8% and then figure out how to install the wires about 1/2" into the orifices and bent the outer end of the wire so that it can't go anywhere.
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-These orifices are usually at the top of the meter blocks and they come out on an angle either left or right, or they are down low near the power valves and go straight inward.
-Reducing the square inch area the equivelant of ONE thousandths is a large change so you should locate or make up a square inch area chart of those small sizes.
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-If you are sharp enough you can find the passage that feeds the transfer slot in the primary side of the main body and thread that to accept an 8-32 setscrew.
-Then measure the slot width and length to get the square inch area of the slot and drill the setscrew to reduce that total at the setscrew.
-Then if you don't like the results you can remove the setscrews.
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-There's nothing about the ported vacuum port that will do anything to help.
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-Take the carburetor off and look at the length of the exposed slots below the primary throttle blades (and the secondary blades).
-If you have much more than about .030" like way up there at say .050" or more, you need to get the blades down on the slot and that means you have to be creative at getting the idle air from someplace beside opening to the throttle blades, like install a PCV valve if you don't have one or maybe holes in the throttle blades up to about .090" or install an "idle air bypass" system.
-To fix part throttle drivability the easiest way is to use a vacuum advance and get the engine all the timing it can stand while it has vacuum.
-The fuel that feeds the transition slot comes from the idle restriction and that is usually around .036" for that size carburetor.
--------------------------------------
-I would run the secondary idles clear in and then back them out only 1/4 turn and do all the rest of the idle mixtures using the primary screws.
-----------------------------------------------
-If you can find the idle restrictions it's fairly easy to restrict the orifices with short pieces of some small diameter wire like maybe a .015" or so.
-You have to measure the orifice do the math of the square inch area and then find wire that will reduce that square inch area by say 5% or 8% and then figure out how to install the wires about 1/2" into the orifices and bent the outer end of the wire so that it can't go anywhere.
----------------------------------
-These orifices are usually at the top of the meter blocks and they come out on an angle either left or right, or they are down low near the power valves and go straight inward.
-Reducing the square inch area the equivelant of ONE thousandths is a large change so you should locate or make up a square inch area chart of those small sizes.
-------------------------------
-If you are sharp enough you can find the passage that feeds the transfer slot in the primary side of the main body and thread that to accept an 8-32 setscrew.
-Then measure the slot width and length to get the square inch area of the slot and drill the setscrew to reduce that total at the setscrew.
-Then if you don't like the results you can remove the setscrews.
-----------------------------------
-There's nothing about the ported vacuum port that will do anything to help.
-----------------------------------------
-Take the carburetor off and look at the length of the exposed slots below the primary throttle blades (and the secondary blades).
-If you have much more than about .030" like way up there at say .050" or more, you need to get the blades down on the slot and that means you have to be creative at getting the idle air from someplace beside opening to the throttle blades, like install a PCV valve if you don't have one or maybe holes in the throttle blades up to about .090" or install an "idle air bypass" system.