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Old 04-29-2013, 05:04 AM   #1
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Default Oil consumption mystery

Here it is. Motor is a 73 500 installed in a 69 F250.

It uses 1 quart of lube oil about every 300 miles.

It fouls the #4 plug about every 300 miles. The residue appears to be 'coke' from oil in the combustion chamber.

I have never seen lube oil burning smoke from anywhere under any conditions, namely the tailpipes.

Exhaust is true dual, stock manifolds, h-pipe, two exits behind rear tires.

When cold or warm but having say for hours, it will blow some oily residue roughly equally from both tailpipes.

If I have only one bad plug from apparent oil related fouling, why do both pipes push the oil? Do H-Pipes 'share' droplets of moisture like this between pipes? I am going to see if I can tell if there is really more from one exit or the other, but very similar.

Why no white/bluish smoke? The engine runs warm, makes good power. Coolant temp runs between 180 and 200 most of the time depending on conditions.

Im thinking one bad valve seal at the number 4, but cant figure out the lack of smoke. Thinking about having someone follow from start to full warm up various throttle settings, or mount a camera back there
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Old 04-29-2013, 01:01 PM   #2
Paul Lane (MTS)
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seems like a lot of oil for a bad valve seal or even a guide
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Old 04-29-2013, 08:16 PM   #3
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other plugs are in the normal range, nothing close to oil/carbon fouling in 300 miles, haven't cleaned any of them in 3-4000 miles.

What also came to mind is how much oil consumption does it take to create constant white smoke, or smoke at every start and for the first few minutes?

Maybe that's more like a quart every 20-100. Any experience out there? Some of it has to do with how the oil is being introduced. I cant figure out how this sludge can make its way out the pipes airborn, but not get hot enough in there somewhere to burn off. Its like the consumption is there while cold or for the first minute or two of run time...coats that plug,,,blows through and quits when everything is hot enough to really burn....
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Old 05-03-2013, 04:27 PM   #4
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I had a 70 500 swapped into a 67 eldo that went through oil and didn't smoke. I wound up pulling it and tearing down for parts and discovered several broken rings. ?? Otherwise it seamed to be a good clean little wear engine. The heads had been redone at some point. I new someone that knew it's history a little bit and found the 70 Eldo had been used to pull a camper trailer between Kansas and Arizona several times. Detination?
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Old 05-07-2013, 01:17 PM   #5
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You should let the engine sit for a day or two while you charge up your battery & then perform a cold engine compression test starting with the cylinder that has the ugliest plug. Make sure you record your readings.

Then add some thick oil to the cylinder with the lowest compression reading through the spark plug hole & perform the test again. If it now has a higher compression reading the chances are that you have a cylinder sealing, or ring pack problem. If not, then you most likely have a valve related problem.

The H-Pipe in your exhaust system will split the burning oil & allow it to go out each tail pipe.

I would also check your PCV (Positive Crankcase Ventilation) system thoroughly. If the crankcase can not vent properly, it will blow oil out of the path of least resistance. A big Cadillac engine requires a good venting system.

Good luck & please let us know what you find out.
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Old 01-31-2015, 02:44 PM   #6
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Decided to bring this one back. I recently purchased some NGK 2322 or BUE plugs to test resistance to oil fouling in the #4. Search them..for a pic. they are a surface gap plug set at .052 thousands. They have no protruding electrode or ground strap. I just ran a 300 mile test from the LA basin to the high desert, Lucerne Valley area, to Landers, and back around to LA via the Palm Springs area.

With a normal plug on several occasion after roughly 300 miles the plug in the #4 would oil/carbon foul and not recover unless removed and cleaned. The engine would use about one quart of lube oil in that same 300 miles and it just repeated that it is consistent. What is not consistent is that this NGK plug did not oil foul. In fact it looked like some deposits were forming, but it is nowhere near as bad a condition as the standard plug. In fact it looks like it may not foul indefinitely.

I ran one of these plugs in the #2 spot as well. On the trip out I turned in 10.0 mpg, for a 64 mile portion of the trip back it got only 7.7 mpg. I felt like the motor was intermittently laying down for some reason about 5-10% or so. It has a Pertronix Ignitor 1 in it, just installed with the specialty plugs. It has a new non-resistor coil wire...the old resistor wire was showing only 3.6v to the coil...pretty low, but strangely the motor seemed to run ok.

These NGK BUE plugs are very 'cold' so I would expect some extra cold running issues. The motor starts very well but then fouls 1-3 plugs in short order unless run up to 2500 rpm...which I don't like to do with a cold motor, but it's either that or run terribly or shut it off. When its hot, it runs fine.

I am not certain if my poor mileage is plug related, but I doubt it. They may be related but I doubt the plugs are more than a slight issue. I have a theory on how these plugs might run differently than the standard plug, but it cam to mind to offer a dyno challenge to MTS.

Here it is: Run a set of these vs. a normal plug or plugs of your choice and compare output on a given motor or motors and share the results... best timing for power etc.

These plugs are not impossible to get, but they are very expensive at some marine places. They were apparently originally developed for some outboard marine engines.

I have run these in a BBC I have with an MSD....motor makes about 500 hp and the motor doesn't seem to care whether it has 4 of them installed or 8. I ran 1 then 4 middle holes then 8. The only difference I noted is it seems to have lessened a slight tip in throttle hesitation, but I think this may be 'timing related' not ignition system wise but what the engine perceives as timng with these plugs versus a normal protruding electrode plug.
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