Ash / Crust on only one Spark Plug Bank

[N C]

Hello, I have a 1988 Dodge B250 that has just reached 200,000. Since buying her we have retained a solid regular maintenance program with fluids, plugs, etc. She has a Rochester Quadrajet Carburetor and a 5.9l 360 engine. We put only about 6-10,000 miles on her annually with much of it being cross country travel rather than city driving.

Yesterday I removed her plugs and found that 1,3,5,7 were heavily ash crusted with relatively white insulators. 2,4,6,8 looked quite good although there were some black spots on the insulators.

I am assuming that it is an oil burning issue because we have no leaks but are going through a court every 300 miles. What would cause only one bank to crust up and the other to be o.k.?

Topic

[Richard Kirshy]

Could be a few possibilities :
Worn valve guide seals.
Manufacturing issue with the block or piston rings.
Could be one side of the engine is running hotter than the other.
Possible difference in air flow from one side of the engine to the other.

Might suggest doing a compression test on all cylinders first
Then a leak down test.

[N C]

Thanks, Richard. I had thought about both of those tests. What about an intake manifold gasket issue?

[Billy]

Pics or it didn’t happen.

[Richard Kirshy]

What about an intake manifold gasket issue?
Not a common issue when oil consumption is that high, unless there are oil passages thru the intake that can breach into the air intake.
I know Chevy’s have oil passages that are sealed apart with the intake, but I do not know if Dodge does something similar.

[N C]

Billy, Sorry. I don’t know how to put up pics. Don’t see a link for that.

Richard, yes, intake manifold gasket is a definite possibility that keeps coming up.

Did a cold compression test today and things looked good there 1,3,5,7 were 150, 148, 148, 148 2,4,6,8 were 150, 148, 145, 148. I’ll do a warm test tomorrow just to see if there is a difference. I know this test won’t tell me the reason for oil consumption but I hadn’t done one in ten years so figured it was about time.

Also did a vacuum test which was good but not as good as it used to be. Idle at about 17 with steady needle although something new was every 20-30 seconds the needle would slowly drop 1.5 then go right back to 17 steady. Don’t know what that was. Throttle snap test was good. Holding her at higher RPM for a bit had a new thing where the needle would go up as expected but it had a serious tremor – not a wide swinging one (example it didn’t even range more than 1″ hg up or down) but a very rapid and not steady needle that I am used to.

[Richard Kirshy]

Might try doing a leak down test to see if there is excessive bypass
Another possibility, you could be dealing with clogged oil rings

[Author]

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