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oil inside exhaust pipe big smoke

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hello again, I have a 1972 Datsun 510 with a L20 engine / 5 Speed transmission. We been restoring her since last year and we were almost finished except something came up with the car. For some reason the cars exhaust pipe has oil in it. When the car is running and i press the gas pedal i get a large smoke cloud, im guessing its the oil in the exhaust pipe. What i want to know is where is the oil coming from??? everything from the Spark plug section is clean. The intake side on the top looks very clean but under the exhaust i see two streaks of oil, one is coming under the two center exhaust ports and 2nd one is located under the last exhaust port . i haven't taken the intake/exhaust out yet but i am curious where that leak is coming from?


 I also changed the valve stem seals but it looks like that little to no effect. is there something else i was suppose to change under there? Spark plugs #4 & #3 are black but that could be me trying to adjust the dcoes.


another question, is the rubber valve stem seal suppose to have a gape between base? Or is it suppose to sit flat on the rotating base?



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First of all was this running properly and then suddenly began blowing oil???? Or is this the first start up????


The spark plugs are clean and not black????? If clean then the oil is burning in the hot exhaust manifold. Only way in is if the exhaust guides are badly worn or the valve seals are not on right or both.




There should be a single inner and outer spring seat washer. All the ones I have seen are stainless steel. Copper seems a bit soft for this. 


The valve guides should stick up out of the aluminum head about 0.400" and the seal should push down and it's lower skirt fit over it.  You should be able to pull the valve out of the head and the seal will stay in place gripping the guide.


Generally oil is more likely to be pulled down the intake valve from intake vacuum than the exhaust which is under pressure. (generally)



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it was running fine before i did all the updates but it was most noticeable when i changed the oil to fresh 10w30 synth in my pre-project days. my pops and i retook off the valve cover and rechecked two of the valve stem seals (the #4 cylinder). We both didn't see too much everything look normal. as for the washers where the spring sit - im guessing holds the outer spring and the silver basic washer holds the inner spring. These are original to the car and i haven't bought them new yet, all valve stems are changed though.


i recheck the spark plugs after i cleaned them - #4 & #3 mostly since they were ones turning black.  #4 & #3 are black now


As for when it smokes well it only smokes when you hit the gas pedal and then you see a cloud of smoke.  unless its burning whatever oil it has in the exhaust pipe/muffer then maybe it may need to stay on for a while ... i dont know. 


Im also trying to find two oil leaks under exhaust headers but its seems like its sealing itself up?  my father and i  both have been carefully  rev-ing and keeping an eye on how much smoke comes out of the exhaust pipe and if there are any leaks when rev-ing the engine

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I would never run synthetic in any Datsun. It works best on tight tolerance engines that actually need the protection, such as having a turbo. Try switching back to something like Rotella T4. See if it goes away.


Oil leaks under the exhaust manifold? or do you actually have a header on this engine??? This can only be oil in the exhaust port that is leaking out past the gasket. 


If 3 and 4 plugs are black then the problem is in the 3 and 4 end of the engine. Valve stems were changed??? Or do you mean valve guides???? Badly reamed or very worn guides will burn more oil than those that are correct and even new seals won't help much. 



Do a compression test. This will eliminate broken pistons and a source of oil.

Did you check how much oil is actually in the oil pan, but NOT using the dip stick yet?


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Mike, know what's funny? when i was deciding on what oil to put in my 720 i was wondering if Rotella would work, and i've seen in a few posts since then, you telling people to use it. I had a bad feeling about using synthetic, so i decided against it. glad i made the decision to stick with conventional. I put Valvoline in on the last change after putting the crap oil through it twice to flush out the water i was talking about.

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Synthetic is over kill which is fine in itself it shouldn't do any harm. My experience is that it leaks past old gaskets and seals because it is too thin or too slippery or both. No Datsun is going to run so clean that you could change it every 12,000-15,000 miles or what ever the claim is. In addition no Datsun in history could go 12,000 to 15,000 miles without topped it up with 4 + liters of fresh oil so???? where's the advantage in that??? Don't run it in a rebuilt engine or it will never break in. I have to assume that synthetic oils do not have ZDDP or reduced levels so has anyone run synthetic long enough to grind up their cams? or will it. We have Datsuns not a 40 year newer, clean running, hi tech EFI engines. 

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16 hours ago, datzenmike said:

New York? 10w30 is fine. If you only drive in the summer 15w40 is also fine. Be sure it's Totella T4 as it has the higher ZDDP levels.


I think he means Shell Rotella? 😆

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Shell Rotella T is a line of heavy duty engine lubrication products produced by Royal Dutch Shell. The line includes engine oils, gear oils and coolants. The oil carries both the American Petroleum Institute (API) diesel "C" rating as well as the API gasoline engine "S" rating. Ratings differ based on the oil. Rotella oils like T3 15w-40 meets both the API CJ-4 and SM specifications, and may be used in both gasoline and diesel engines. However, it is formulated specifically for vehicles without catalytic converters, containing phosphorus levels beyond the 600-800ppm range.[1] Therefore, Rotella is not recommended for gasoline vehicles with catalytic converters due to the higher risk of damaging these emission controls.[citation needed][2] Newer formulations of Rotella T6 however are API SM rated as safe for pre-2011 gasoline vehicles.


Shell is marketing their new CJ-4/SM oil as "Triple Protection," meaning it provides enhanced qualities for engine wear, soot control and engine cleanliness. Shell's Rotella website indicates that on-road testing confirms the new Triple Protection technology produces better anti-wear characteristics than their existing CI-4+ rated Rotella oil. This is achieved despite a lower zinc and phosphorus additive level as called for by the API CJ-4 specification. (The 15W-40 Rotella T with Triple Protection oil has approximately 1200 ppm of zinc and 1100 ppm phosphorus at the time of manufacture.)



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