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Old 11-26-2012, 08:15 PM   #1 (permalink)
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Default Oil Consumption Mystery

I have about 3,000 miles on a 347 I assembled last summer and for some reason the rings havenít seated. Iím getting 145 to 155 psi compression on all cylinders (10.3:1 compression ratio) and about 20% leak down. The engine runs great and has good power, but the big issue is that it is burning a quart of oil every 500 miles or so and I canít figure out where it is going. The following is a list of things Iíve observed.

There is no blue smoke coming out of the exhaust under any driving condition.

The tailpipes are not oily and the spark plugs are light tan with no indication of oil.

There is no oil leaking from the engine, the engine bay and underside of the car are very clean and there are no oil spots on the garage floor.

There is no indication of oil in the coolant.

The oil got dark very quickly, which I assume is due to the blow-by.

When I built the motor, all of the top compression rings were gapped between 0.017-0.018, and the lower compression rings were gapped between 0.020 and 0.022.

Iím running Valvoline 20w-50 oil.

When the electric fan cycles off I can see smoke coming out of the valve cover breather. When the fan is on the smoke isnít obvious.

The PCV system is working fine.

There is a baffle plate in the valve cover where the PCV valve fits in.

Since Iíve been running the motor, Iíve burned about 5 quarts of oil. If all of this were coming out of the breather Iíd expect to see a lot of oil film in the engine bay. There is some, but not much.

Any ideas on where the oil is going? At this point, Iím figuring it is going out the breather, but Iím not sure. I plan on rebuilding the engine soon to deal with the blow-by, but I want to make sure I also fix the oil consumption problem at the same time.

Thanks for any suggestions.

Dan
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Old 11-26-2012, 08:27 PM   #2 (permalink)
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20w-50 seems kind of thick.
I'm not sure what normal break in weight oil is for these motors but normal running oil is 10w-30. That is what I've always used in the past with no problems.
Lynn
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Old 11-26-2012, 09:07 PM   #3 (permalink)
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Quote:
Originally Posted by ponyexprez View Post
I have about 3,000 miles on a 347 I assembled last summer and for some reason the rings havenít seated. Iím getting 145 to 155 psi compression on all cylinders (10.3:1 compression ratio) and about 20% leak down. The engine runs great and has good power, but the big issue is that it is burning a quart of oil every 500 miles or so and I canít figure out where it is going. The following is a list of things Iíve observed.

There is no blue smoke coming out of the exhaust under any driving condition.

The tailpipes are not oily and the spark plugs are light tan with no indication of oil.

There is no oil leaking from the engine, the engine bay and underside of the car are very clean and there are no oil spots on the garage floor.

There is no indication of oil in the coolant.

The oil got dark very quickly, which I assume is due to the blow-by.

When I built the motor, all of the top compression rings were gapped between 0.017-0.018, and the lower compression rings were gapped between 0.020 and 0.022.

Iím running Valvoline 20w-50 oil.

When the electric fan cycles off I can see smoke coming out of the valve cover breather. When the fan is on the smoke isnít obvious.

The PCV system is working fine.

There is a baffle plate in the valve cover where the PCV valve fits in.

Since Iíve been running the motor, Iíve burned about 5 quarts of oil. If all of this were coming out of the breather Iíd expect to see a lot of oil film in the engine bay. There is some, but not much.

Any ideas on where the oil is going? At this point, Iím figuring it is going out the breather, but Iím not sure. I plan on rebuilding the engine soon to deal with the blow-by, but I want to make sure I also fix the oil consumption problem at the same time.

Thanks for any suggestions.

Dan
I had the same problem, if its not coming out the tail pipe then you gotta leak. I had been chasing this problem and found vavle covers come lose and the nipple for theoil sender not being tight enough. What a difference it is to look from the bottom up with a good flash light.
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Old 11-26-2012, 09:43 PM   #4 (permalink)
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Time for Bon-Ami......

Okay, seriously, you may not want to try the old-fashioned approach to ring sealing. It's probably evident that you're going to need to do a tear down and find out what is going on.

You know you have a blow-by/leakage issue, but what's the scoop with the oil-control rings? They should be scraping the cylinder walls and the blow-by should be clearing them. I question whether the finish of the bores is compatible with the ring mfr's specification, if the rings were installed correctly, etc. You should know for sure once you pull a cylinder head....
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Old 11-26-2012, 11:00 PM   #5 (permalink)
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20W50 on a fresh motor seems too thick for me. As for the oil consumption, I had a similar problem with a set of Tony Branda tall valve covers.(link below) They also had baffle plates, but they were to small. Small amounts of oil were misting out of the breather cap at higher rpms and on the PCV valve side were getting sucked into the carb. The car didn't smoke or show signs of the pcv valve sucking oil until I was working on the carb. Intake runners and valve were soaked in oil.

Tall Polished Cobra Valve Covers for 289-302-351W
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Old 11-27-2012, 05:57 AM   #6 (permalink)
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Something else to check.....
If you find no trace of a leak, and your plugs indicate that combustion is acceptable with no oily residue, you might be pulling oil past your exhaust valves into the exhaust manifold where it is burned. This generally occurs when accelerating, and the tell-tale blue smoke is really difficult to see. That would indicate valve stem seals are not doing their job. The original Ford umbrella style seals are marginal at best. The clamp-on style seals seem to work best - can't come up with what they are called at the moment. Check with your machine shop for more info.
Best,
Al
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Old 11-27-2012, 09:01 AM   #7 (permalink)
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Quote:
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20W50 on a fresh motor seems too thick for me...."
Not at all. You might be giving up some fractional horsepower, that's the only negative. I've been using Mobil 1 15w-50 in all classic cars that I owned, and worked on, for over 12 years. At least some 200,000 cumulative miles driven in extreme conditions. Over 50,000 miles on one '66 GT350 with these results: no leaks & no measurable wear.

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Old 11-27-2012, 09:32 AM   #8 (permalink)
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did you check the rear main seal?
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Old 11-27-2012, 03:55 PM   #9 (permalink)
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Thanks for all of the feedback. I'll look into the suggestions and let everyone know what I find.

Dan
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Old 11-27-2012, 04:19 PM   #10 (permalink)
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Did the wrist pins go through the lower ring set? I know the older/less expensive 347 kits did and they were known for burning oil.
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Old 11-27-2012, 10:21 PM   #11 (permalink)
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Quote:
Originally Posted by higher power racing View Post
Did the wrist pins go through the lower ring set? I know the older/less expensive 347 kits did and they were known for burning oil.
Yeah, the wrist pin does go through the oil control ring groove. They're Probe pistons that came in a kit I bought from Ford Strokers, so I'd assume they're good quality stuff.

Dan
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Old 11-27-2012, 10:50 PM   #12 (permalink)
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You could put an oil catch can in line with the pcv to separate any oil running through your pcv system. Cheap and easy way to eliminate one variable.
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