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Discussion Starter #1
Have a 390 Fe Motor with a road draft tube (no PCV). When I bought the car, it ran great. No smoke. I took it in to a shop for oil change and to have some of the leaks fixed. Got it back after oil changed to synthetic with oil stabilizer and the valve cover gaskets replaced. Once it warmed up there was a moderate amount of smoke coming from the roaddraft tube. Also some steady dripping of oil. Another visit to shop and an intake manifold gasket took care of the drip (still a few leaks I think rear main). However the smoke from road draft tube is still present once the car warms up. Seems to be heavier the warmer the engine is or longer it runs. Some also from oil breather at front of intake manifold. My question is could an different oil cause this smoke issue? Odd it didn't smoke at all previously and I drove it 35 mins in high 80s weather. Your advice/experience is welcome!
 

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yes. changing types of oil can affect your old car . #1 fe engine likely wont do well with synthetic as the tolerances are quite different than modern cars. crankcase pressure (blowby) can increase with different viscosity oil.
change back to old type oil and see if the problem goes away
 

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Discussion Starter #3
Thanks. Any suggestions on what oil to use on a 80k 390FE motor? I am not sure if ever rebuilt. Only had 2 months.
 

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Yeah synthetic oil is thinner, and therefore goes past certain parts of the engine that heavier weight oil cant goes through. I wouldn't use synthetic unless the motor was completely rebuilt. I use 10W30 in my 66 galaxie with a 390 with 150,000 miles on it and have never had a problem. I go with valvoline due to better overall ratings
 

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Are you positive that there was no smoke? cause with a draft tube Ive never seen one not smoke it is what they do. If you have moisture in your oil it will be more. I know my 292 smokes quite a bit if I don't run it much but if I put fresh oil in it or after I burn the moisture out with some driving the amount of smoke reduces at idle.

Ive ran 10w30 and 20w50 oil in my 292 with draft tube and there was no change in amount of smoke coming out of the draft tube system. This might be a issue with synthetic oil or if its a synthetic blend that is causing this.

Have you checked your filter that its clean? draft tube setups have filters, some like the Y blocks like my 292 actually have two filters, a fresh air inlet filter at the draft tube in the side of the block and one at the filler in the lifter valley. 390`s how ever don't have that filter they only have the filter at the filler tube. Only reason why I know that is I pulled a 65 galaxy`s 390 four times due to a cam going flat.
 

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if you don't have pcv and have no reason to keep it totally stock, you really should add the valve. your engine will thank you by lasting much longer
 

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Discussion Starter #8
No smoke before. At least not enough to notice. We drove it 40 miles round trip in high 80s weather and didn't have a lick of smoke that was evident.
 

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Discussion Starter #9
The mechanic changed the breather head where you fill the oil. He mentioned going to pcv with a different breather cap but it would just divert back into motor and out tailpipes not really solving the smoke issue. At least that is my understanding.
 

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if you don't have pcv and have no reason to keep it totally stock, you really should add the valve. your engine will thank you by lasting much longer
I agree, I have been throwing around doing the California mod on my 292 as they were required to have PCV systems. We at work tried to talk the customer with the 65 galaxy that I pulled the 390 out of multiple times for a cam going flat on the same lifter bore. He didn't want to do that as he wanted to keep it original.
 

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The mechanic changed the breather head where you fill the oil. He mentioned going to pcv with a different breather cap but it would just divert back into motor and out tailpipes not really solving the smoke issue. At least that is my understanding.
The smoke might not necessarily be smoke though. It just simply blow by on your rings which being fed back into the engine would not be seen out the tail pipe. Could also be condensation as well which wouldn't be seen out the tail pipe either.

If you were actually burning oil for instance it would have to be happening in the cylinder which means it wouldn't be smoking out of the draft tube but smoking out the tail pipe. Oil in the crank case wont burn, but moisture in the crank case can turn to steam once heated up. Like wise blow by on your rings can also result in combustion being blown into the crank case providing smoke as well.
 

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that moisture in the crankcase will combine with the sulfur in the gas to make sulfuric acid which will eat up your engine. california started mandating pcv to stop all the smoke in the cities where cars were sitting idling alot. road draft systems only work at speed using the venturi effect to move the blowby gasses out of the engine. it doesnt work at low speeds. pcv is the one emissions system that all manufacturers adopted because it increased the engine longevity
 

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Discussion Starter #13
Thanks for the advice. I am going to try and find another mechanic in the area that's good with old cars. I can handle the oil change, but if that doesn't remedy it...I need a back up plan. I am guessing only about 30-40 miles are on it since the oil change.
 

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no. the air needs to circulate through the engine. the common fix(if you cant find the factory pcv adapter) is to put a core plug(you probably call it a freeze plug) in the draft tube, and drill a hole in the top of the draft tube to insert a pcv valve. i have seen a few block to pcv valve set ups on e bay. bolts on where r. drft tube mounts. there should be a filter of sorts in the block when you remove the draft tube---looks like steel wool
 

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no. the air needs to circulate through the engine. the common fix(if you cant find the factory pcv adapter) is to put a core plug(you probably call it a freeze plug) in the draft tube, and drill a hole in the top of the draft tube to insert a pcv valve. i have seen a few block to pcv valve set ups on e bay. bolts on where r. drft tube mounts. there should be a filter of sorts in the block when you remove the draft tube---looks like steel wool
That's what we were going to do on our customers galaxy`s 390, was going to seal a plug in the draft tube mount install a grommet and mount the PCV valve there.
 

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yep. since theres no holes in the valve covers., the air enters at the oil fill and exits at the draft tube. change it so it exits the draft tube through a pcv valve and into the manifold
 
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