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Discussion Starter · #1 ·
Man, I feel like New England's footballs, DEFLATED!!!
My new purchase, a 56 with a 327 motor was missing badly, and emitting a black soot on startups. Dirty carburetor, bad vacuum advance, fouled plugs , Dwell advance. Lube and oil using 20/50.
Fixed everything last week and put about 300 miles in it over the last few days. It was running fine. Didn't run it over 70mph.
The black soot is back, and now it is burning oil like a furnace. 2.5 quarts in 300 miles. It doesn't smoke or emit soot until I gun the motor or accelerate hard on the road.
It idles smooth, and doesn't heat up.
The person I bought it from told me he was having problem with the valve guides leaking oil. He never used it much, and was inop for about 6 mos.
I've got my other 56 being stripped and painted. I don't want another major expense. I don't mind a valve job on this one but I hope not a ring job. A compression test last week was a little erratic. From 125 to 145. I didn't think it was too bad since the lowest was at 125.
Anyone with a similar problem? :confused0024:
 

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Discussion Starter · #3 ·
Thinking out loud, what I want to believe is that it is the valve guide seals. I believe there must be at least two or three really bad seals. The previous owner didn't drive the car much. I've probably put more miles on the car in two weeks, than he did it in two years. He knew about the bad seals,
My thinking is that the seals may have pretty much decomposed, causing excess oil consumption. As I said the compression test did not reflect the engine had terribly worn out rings. IMHO, compression of 125 to 145 is not that bad.
I had the oil changed using 20/50 oil. I imagine a high viscosity oil. I filled it back up with Mobil High Mileage oil. At 10 bucks a quart, it better do something :).
 

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Discussion Starter · #6 ·
sounds like seals/valve guides? If in doubt, do a leak down test too.
I had a compression test done. That's why I'm leaning towards valve guide seals. A leak down test will only tell me if I have leaky valves or rings correct? I had this done with my other chevy. I found I had cracked valve seats.
 

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I'd pull the valve covers and check the oil return holes in the heads. If they are plugged oil can be above the valve guides and will pour through decent intake valve guides, let alone worn ones, seals or no seals.
 

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You mentioned that the plugs were replaced being that they were fouled. If the firing end of the plug have a wet oily coating? This would indicate poor oil control and some oil is leaking past the rings or valve guides and another common cause could be a bad/plugged PCV valve= bluish smoke.A hotter range plug may temporarily this problem. If the plugs were carbon fouled they would have a dry,soft,black sooty deposits. If the heat range is correct,fouling can be attributed to a sticking choke,too rich carb fuel mixture,ign. timing retarded,carb float levels high,bad plug wires to affected plugs,distributor cap cracks.In this case you have incomplete fuel combustion= black-grayish soot/smoke. Hope this helps,good luck. Keep us updated. Bob :bowtieb:
 

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The blue smoke is oil, with that oil consumptiom you must have bad rings. The black smoke indicates to me a rich fuel mixture.

Joe
 

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Discussion Starter · #12 ·
I'd pull the valve covers and check the oil return holes in the heads. If they are plugged oil can be above the valve guides and will pour through decent intake valve guides, let alone worn ones, seals or no seals.
Could be. That would explain the excessive oil consumption. I'll find out on Wednesday.
Currently working on getting the lamps in my gauge/speedometer panel to light up. Bypassing rheostat and running switched 12vdc directly to lamps. Tried to come off ignition switch. I could see a couple of unused tabs, but couldn't get my probe to them without risking a short. Too lazy to disconnect voltage then looking for a switched 12vdc tab. I'll do that tomorrow, or just run power to the lamps via a sp/st toggle switch. couldn't find a small rheostat anywhere. I'm risking leaving the panel lights on. I hate having the headlights remaining powered after turning off the car.
 

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Could be. That would explain the excessive oil consumption. I'll find out on Wednesday.
Currently working on getting the lamps in my gauge/speedometer panel to light up. Bypassing rheostat and running switched 12vdc directly to lamps. Tried to come off ignition switch. I could see a couple of unused tabs, but couldn't get my probe to them without risking a short. Too lazy to disconnect voltage then looking for a switched 12vdc tab. I'll do that tomorrow, or just run power to the lamps via a sp/st toggle switch. couldn't find a small rheostat anywhere. I'm risking leaving the panel lights on. I hate having the headlights remaining powered after turning off the car.
I suggested checking the oil return holes because I've had the smoking/ burning oil problem on a '70 Jeep J30 4x4 PU 350 and a '90 Caprice 305. Both (mostly) stopped smoking when cleaned up with kerosene, an oil change, and v/c gaskets.
 

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Discussion Starter · #14 ·
You mentioned that the plugs were replaced being that they were fouled. If the firing end of the plug have a wet oily coating? This would indicate poor oil control and some oil is leaking past the rings or valve guides and another common cause could be a bad/plugged PCV valve= bluish smoke.A hotter range plug may temporarily this problem. If the plugs were carbon fouled they would have a dry,soft,black sooty deposits. If the heat range is correct,fouling can be attributed to a sticking choke,too rich carb fuel mixture,ign. timing retarded,carb float levels high,bad plug wires to affected plugs,distributor cap cracks.In this case you have incomplete fuel combustion= black-grayish soot/smoke. Hope this helps,good luck. Keep us updated. Bob :bowtieb:
You've hit on a few things I recognize Bob. Definitely fast idle. Idle was set at 650, but idling probably closer to 8 now. Don't have a tach on it yet. Choke is not hooked up and doesn't use a PCV valve. Even though engine is a 327 it uses a downdraft tube.
Most of the old plugs had the soft black film around the electrode. The carburetor was overhauled, but I'm not too happy with the way it ran. I have another carb I was using on my 265 before I converted to 4bbl. I'm going to remove the vc's and check the seals and I'll let the engine run to see what my oil flow is like...one side at a time. I'll swap over to my old carb.
 

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Discussion Starter · #15 ·
The blue smoke is oil, with that oil consumptiom you must have bad rings. The black smoke indicates to me a rich fuel mixture.

Joe
I can't quite agree with all three of your observations Joe. I'm far from being an expert mechanic, so I rely on logic a lot.
Yes, popular consensus is that Blue smoke is oil, but black smoke means unburnt fuel. The fuel mixture may be correct, but if my plugs are getting fouled by oil seeping past the seals, this would cause poor plug detonation. Thereby allowing unburnt fuel to exit out my exhaust pipe in the form of soot and liquid.
There's enough debate in this thread, that should provide enough variances on why there's excessive oil consumption and poor fuel usage in an engine that seems fine otherwise
 

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Discussion Starter · #16 ·
I suggested checking the oil return holes because I've had the smoking/ burning oil problem on a '70 Jeep J30 4x4 PU 350 and a '90 Caprice 305. Both (mostly) stopped smoking when cleaned up with kerosene, an oil change, and v/c gaskets.
I'm sure the problem is more than one. I think I'm looking for two or three solutions. Probably not a bad idea to clean out some of the oil returns, but I might have to go to Ohio for Kerosene. I haven't seen that stuff around here for a long time. One concern I have with doing this is creating sludge that might make things worse around small orifices.
 

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2.5 qts oil consumption in 300 miles is way worse than bag valve guides and seals. you might have a lower intake leak in the lifter valley area. if vacuum is good and idle is smooth not likely. most would agree you are probably looking at a ring issue. You can have a good compression check and still have bad oil control rings.
 

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Discussion Starter · #18 ·
OK, say it is bad rings, which I don't believe, I can't explain why the exhaust at start up is mostly black soot with liquid which may be half spent gasoline. It is not a big puff of blue smoke. I can't explain the high oil consumption but most of the 300 miles I drove was at speed in excess of 60mph. A couple of hills, but mostly flat and cool temp.
 

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the liquid at start up is condensation in the exhaust system that is being cooked out as it warms up, if it was actually unburnt gas it would not run. the black soot is rich fuel mixture from start up, choke is probably set too rich. what carb do you have perhaps it needs to be re jetted.
 

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Discussion Starter · #20 · (Edited)
the liquid at start up is condensation in the exhaust system that is being cooked out as it warms up, if it was actually unburnt gas it would not run. the black soot is rich fuel mixture from start up, choke is probably set too rich. what carb do you have perhaps it needs to be re jetted.
I've already had the carb overhauled once. I didn't like the way it came back. We've adjusted it so that it runs OK, but I'm not happy with it. I'm going to replace it with a known good one I own. It came off a 265 but I think this is a later carb as it was hooked up to a PCV valve. This one on the 327 seems older. No PCV valve. and the choke is not hooked up.
That might explain the soot, but the oil consumption is unrelated. Yes/No???
Carbs are both 2bbl Rochesters.
 
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