plug fouling

[prg machine]

My engine started an intermitent miss and stuttering that came and went and made me think I had valves sticking in the odd numbered (left) bank of the engine . I finaly pulled plugs and number 1 and 3 looked normal with a tan to white insulator and some very faint white ash build up around the ground lug and down inside the barrel. pretty clean for the most part. Number 5 and 7 were fouled with a dark grey to black crusty/carbon build up bridged along the inside of the ground lug and reaching to the insulator. Very hard to remove with a dental pick. Almost welded like. The electrode was not bridged and was still firing for the most part but I could see where this was my problem of misfires on occasion.
I cleaned em up and re-installed and runs great. I need to check the even numbered bank tommorow. The engine has not quite 3,000 miles, still running 30 wt. changed after 500 and once again at another 1000 and due now to change to something different. I was thinking a 10-40 Castrol might be a good choice.
Why just number 5 and 7?
I am running Autolite 26 plugs. I am getting in to a shop for air fuel mixture scope analysis to check the jetting as well. The plug wires are all brand new MSD and are not damaged in any way.
I know this is old wives tale stuff..................but is there some misfire problems between the number 5 and 7 cylinders due to wire routing?


Any advice??

I don't understand why 2 plugs were in this condition unless there was residual break in oil in those 2 cylinders? Engine does not smoke, runs real strong. The misfiring would develop after a period of low speed running or de-acceleration and high vaccuum.

[jhow66]

Could be damaged valve seals on those two cylinders (or missings). Could be damaged intake gasket (at bottom) pulling oil into those two ports from lifter galley at times of high vaccum-best bet. Crossed plug wires on 5 & 7?

[prg machine]

I am checking that theory of inductive crossfire on 5 and 7 tommorow. I used the new Edelbrock gaskets when setting the intake down.............not ruling that theory out though.
The crossfire thing is my bet, even though MSD says their technology "prevents" crossfire , does not totaly rule it out. I wish I could find something about what I was told many years ago about how to cross over certain wires to prevent the crossfire thing, but I can't seem to be able to find it on Google.
I plan on making sure that 5 and 7 aren't running close together like side by side .

[jhow66]

I was talking about having #5 wire plugged on # 7.

[El Jay]

This may sound really stupid to you.
Do you park the truck facing "uphill"?

If the valve seals on those 2 cylinder are bad, the oil on the top of the heads could be draining "downhill" and through the valve seals & into the cylinders.

Just a thought. A friend of mine had a similar problem with his Chevy van, maybe 20 years ago, or more.

[prg machine]

It seems that I might have a fuel mixture problem with carb. I am getting it annalyzed ASAP

[spinning wheels]

Seems like you have done a lot of troubleshooting already.

What distributor are you using?

Check your dist. cap for any moisture or cracks.

[prg machine]

The MSD billet dizzy. I seperated out the 5 and 7 wires completely away from each other and told the guy at the test shop I called about the old theory of crossfires and he doubts that with the MSD wires that would happen. He strongly expects the fuel/air mix-jetting.
I will check the cap however.

[prg machine]

An important point came up today.....................'are there baffles in those valve covers?" I was asked.....................no I said.

There is a strong chance this could be the problem, maybe. I have some baffles to instal under the PCV valve to keep oil from getting sucked into intake. The problem is coming from upper end oil.
The intake leaking theory was ruled out by the guru who demonstrated with a piece of paper over the breather hole that there was no suction with the PCV valve un hooked from the opposite cover. If there was, it would indicate manifold suction from a leak at the intake manifold sucking through the cranck case.

I will keep this updated as I get down to it.

Valve stem seal or guide leakage is not ruled out however.

[prg machine]

baffle under the PCV grommet in valve cover did the trick! Truck is running better than ever. Oil consumption is no more as well.
For once, big problem, little fix!!!!

[prg machine]

Originally Posted by jhow66

Could be damaged valve seals on those two cylinders (or missings). Could be damaged intake gasket (at bottom) pulling oil into those two ports from lifter galley at times of high vaccum-best bet. Crossed plug wires on 5 & 7?

The plugs are fouling again. Had a shop check intake valve stem seals. They are perfect circle and in good shape and stem clearance is as it should be. ( Only 10,000 on rebuilt heads and engine) The exhaust seals were stock and the I had the shop replace with umbrella seals.
Runs great with new plugs. Next week it is getting new manifold gaskets............thicker. I believe the head angle and manifold angle could be mismatched enough to cause a problem on the galley side.

More later..................( after the pocket book is empty!)

[prg machine]

CURED! The intake manifold gaskets were just too tall enough that the raised boss of the gasket didn't seal properly to the bottom of the manifold because the bottom edge wasn't seated allowing oil seepage. Not enough to cause vaccuum loss that was noticeable, but enough to get oil vapors.




I ditched the 1 inch phenolic carb spacer as well and now there is more bottom end off the line and a smoother start for street use.

[mclairmo]

What brand gasket was the problem one? Also, was your spacer 4 hole or open?

[prg machine]

felpro if I remember correctly is what Edelbrock reccomended. Mr. Gasket in there now

4 hole Summit Phenolic.

Runs so much nicer without it.

[airdale94]

Yes, never run the the plastic Fel-Pro with a aluminum manifold. Use the cardboard Mr. Gaskets. Had the exact same problem.

[prg machine]

I copied this from the instruction page on line from edelbrock. I ordered these and they caused the problem.




(copy):

• GASKETS: Do not use competition-style intake gaskets for this street manifold. Due to material deterioration over time,
internal leakage of vacuum, oil, and coolant may occur. NOTE: YOU MUST USE a factory metal valley tray gasket along
with the Edelbrock gaskets listed below. If your stock valley tray is in good condition, it may be re-used.
INTAKE MANIFOLD REFERENCE RECOMMENDED GASKET
7530, 7531 (None) Edelbrock #7213; Port: 1.13” x 2.21”, .030” Thickness


Anyway. Mr. Gasket now.

[highperf4x4]

Something sounds fishy to me but if it's running good, not fouling plugs, and not burning oil then I guess you're ok.

I would be suspicious of the rings and the valve seals both if it were me. There are 3 things that can foul a plug, gas, oil, water. Each of them put out a different color of smoke. Black, bluish grey, and white. If you fouled a plug no matter where the gas, oil, or water came from, it should have been smoking. Black would be fuel, blue or grey would be oil, and white would be water. If the plugs had a dull black buildup on them it's usually fuel. If it was gummy and shiny black it's probably oil. These can be hard to discern sometimes. However, if the plug had a brown buildup it's definitely water.

I don't know what intake you're running but I've never seen one that was so misaligned with the gaskets that you could suck oil into a cylinder without shooting coolant into the oil from the head whether you have a blocker in place or not.

Just doesn't sound right to me.

[prg machine]

You'd have to see the gasket compression pattern to fully understand. Oil fouling on three cylinders. Mismatch on those same three was at the bottom of the intake ports causing oil vapor to suck in especialy under de-compression when the vac gauge was reading over 20 lbs. The replacement gaskets were not as tall and consequently seal where they need to. The engine is running like it never has. 10,000 miles on engine, no smoke, blue or otherwise.
I am monitoring oil consumption for now. Before the manifold came off for the new gaskets Oil consumption was at 1 qt / 500 miles since new when engine was first stared up. you could smell it in the exhaust and see blue smoke if the humidity was up when backing up on a cold morning.

There was a film of oil along the bottoms of those same 3 port runners as well indicating oil intake at that point. The intake valve stem seals were in good shape and were the Perfect Circle brand. Umbrella seals and new o-ring seals were installed on the exhust valve stems for good measure.


Like I say I am monitoring oil consumption and so far so good with performance. Detonation is not an issue anymore as well since oil will lower octane level.


I am currious what Edelbrock means by the stock oil splash shield however. I have one on a Buick engine, but it has an open galley to the crankcase. The Chevy has a closed galley. I have never seen one in a Chevy engine..................but my engine experience is limited to just a few.

[prg machine]

I might ad that the oil pattern was very noticeably on one side of the plug indicating not coming from the bottom end or rings. Top end leakage definitely.

[mclairmo]

I believe some intakes have a splash shield riveted or attached to the bottom somehow.

[highperf4x4]

Well, it sounds like you've done the research and found alot of good evidence. Best of luck with it now and thx for sharing you're experience.

Originally Posted by mclairmo

I believe some intakes have a splash shield riveted or attached to the bottom somehow.

That is correct.

[prg machine]

Originally Posted by jhow66

Could be damaged valve seals on those two cylinders (or missings). Could be damaged intake gasket (at bottom) pulling oil into those two ports from lifter galley at times of high vaccum-best bet. Crossed plug wires on 5 & 7?

Seems to be the case

[airdale94]

PRG- yeah they always say that about the hp gaskets. But you know the plastic Fel-Pros don't work. What it is, it's your new Edelbrock intake is warped. I had to have .060" planed off of one of my new Edelbrock's. You should be allright with the Mr. Gasket at least 60k miles for it's starts to deteriorate

[prg machine]

Originally Posted by airdale94

PRG- yeah they always say that about the hp gaskets. But you know the plastic Fel-Pros don't work. What it is, it's your new Edelbrock intake is warped. I had to have .060" planed off of one of my new Edelbrock's. You should be allright with the Mr. Gasket at least 60k miles for it's starts to deteriorate

GREAT!!! more good news