Oil out of breather - Vintage Mustang Forums
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post #1 of 16 (permalink) Old 06-12-2019, 11:58 AM Thread Starter
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Oil out of breather

Looking for some guidance dealing with oil coming out of my driver side crankcase breather. The passenger side has the PCV installed. It's enough oil that it is coming out and hitting the headers which causes smoke and smell that can be seen while sitting still. It's a 351w stroked to 408 and runs good aside from this issue. It's a motor I had built 2 years ago but I refuse to deal with the builder anymore after several glaring mistakes that caused me to install and pull the motor twice after delivery of the motor.



Anyways, any and all help great appreciated. Also, visual references would be great, i'm definitely better when I see what people are referring to.

1968 Mustang Coupe 408W
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post #2 of 16 (permalink) Old 06-12-2019, 12:08 PM
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Could be that there's no baffle inside the valve cover, which means more oil splashing up through the hole. No easy fix for that except to get different valve covers, probably. If your engine is running rough, you might want to do a compression check to make sure your rings are doing their job. If they are not sealing well, the blow-by from exhaust sneaking past them into the crankcase can lead to excessive oil and smoke shooting out your breathers. Lastly, it could just be that your PCV valve/hose is clogged. If it's stuck closed, then none of the fumes in your crankcase are getting sucked out. That means the only place they can go is out your other breather, so it'll keep spitting oil and smoke.

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post #3 of 16 (permalink) Old 06-12-2019, 12:08 PM
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Typically the result of insufficient media in the cap to collect the oil vapors and condense them to droplets heavy enough to drop back into the valve cover. Could also be poor baffling at the inside of the filler hole.
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post #4 of 16 (permalink) Old 06-12-2019, 04:07 PM Thread Starter
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I'm pretty sure the valve covers have baffles, but i'll double check. I'll also check the PCV valve and hose and get back with a response hopefully late tonight. Thanks for the help guys.
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1968 Mustang Coupe 408W
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post #5 of 16 (permalink) Old 06-12-2019, 04:56 PM
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You could run a hose from the valve cover to a remove catch-can with a breather on top. The larger can will collect the oil that will have condensed into smaller drops by the time it gets there and the breather will let the blowback escape. I have something like this on my Cobra replica with a 347 and it helps keep my valve covers clean (not running a PCV on that car)
https://www.summitracing.com/parts/m...YaApSaEALw_wcB


Are you running a closed PCV system where you have a breather in one valve cover and the other side connected to the base of the carb? If not, do you really even need the PCV valve? Just run a hose from each valve cover to a remote breather and your engine will stay clean.

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post #6 of 16 (permalink) Old 06-12-2019, 05:30 PM
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For some reason you have too much crankcase pressure. Two main factors a plugged PCV valve or hose to the carb or excessive blowby. Being it's two years old and you had issues with the builder and at 2 it's unlikely to be a plugged PCV sytem I would suspect too much blowby.
Most likely cause in an engine that new would be a blown head gasket as it's unlikely to be from cylinder wear even on a poorly built engine unless really really bad.

A cylinder leakdown test is where I would start after a cylinder drop test.
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post #7 of 16 (permalink) Old 06-12-2019, 08:27 PM
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it's hard to say (meaning hard to tell how much blowby you really have), but it could simply be the normal case of more cylinder pressure/higher rpm (e.g. HP) WILL result in more gas's entering the crankcase (rings aren't a perfect seal).

that extra crankcase pressure has to escape somehow with some trying to push out the PCV to the intake and the rest out the other breather. some cars return that other breather to the air cleaner so it's not dripping on your valve covers....

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post #8 of 16 (permalink) Old 06-12-2019, 09:14 PM
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My old 351w always had a small amount of oil leaking out the driver side breather. Not enough to cause a noticeable amount of smoke.
It had stock valve covers with baffles, a functional pcv, and good compression.
Probably just a crappy breather cap.

As mentioned, a remote breather catch can might help.
Or you can connect a hose from a ported breather to a port on the air cleaner base.

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post #9 of 16 (permalink) Old 06-12-2019, 09:33 PM
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Quote:
Originally Posted by Iceotron View Post
Looking for some guidance dealing with oil coming out of my driver side crankcase breather. The passenger side has the PCV installed. It's enough oil that it is coming out and hitting the headers which causes smoke and smell that can be seen while sitting still. It's a 351w stroked to 408 and runs good aside from this issue. It's a motor I had built 2 years ago but I refuse to deal with the builder anymore after several glaring mistakes that caused me to install and pull the motor twice after delivery of the motor.



Anyways, any and all help great appreciated. Also, visual references would be great, i'm definitely better when I see what people are referring to.
Although it won't solve why you have blow by but, you could always install a crankcase evac system--a bung on each header (or exhaust tubes) and connected to each valve cover. Get really fancy and install a vacuum pump evac system but that is more for big boost combos. We went that route in the race car but it was a partial sponsorship deal ( we made 27 lb at 7500 rpm and 757 RWHP) but totally overkill for your application. Personally, I'd want to find out why you have the blow by.

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post #10 of 16 (permalink) Old 06-13-2019, 12:14 AM
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How hard do you drive it? Does it happen all the time? Only after spirited high rpm exercises? What do the spark plugs look like? A second breather may help...

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post #11 of 16 (permalink) Old 06-13-2019, 09:49 AM Thread Starter
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https://www.ebay.com/itm/SBF-Black-P...-/151703817687


These are the valve covers i'm using, and they do have baffles. I drive the car spirited, I drive it to and from work which is about 40 minutes each way and mostly highway. However, I do go over 4500 rpm at multiple points throughout the trips. As far as I can tell it happens every time I drive the car, about 2 times a week on average when the weather is nice and no rain in the forecast. I'm in Buffalo so winter driving is out as well. When I start the car and until it warms up the oil pressure is at 50-60 lbs at idle and then when completely warm settles in to 15-20lbs. Not sure if this is or isn't a factor as well. I'll pull a plug tonight to see how it looks, i'll try to take a pic and upload it here.



I was thinking about giving this a try for now and then try and diagnose the root cause once the driving season is over. Any concerns about this approach? Would I be causing more issues?
https://www.amazon.com/Vincos-Univer...3H7SE239Q95FKH

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post #12 of 16 (permalink) Old 07-08-2019, 09:53 AM Thread Starter
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Quick update, I installed the above and then it got worse, much worse. Compression check found that cylinder 7 had 0 and cylinder 4 had 30. The rest were between 120 and 130. I stopped diagnosis there and pulled the motor on Saturday. Now I need to find time to bring it to the builder. 543 miles since he built it. I'll update again once I get it there and we tear it down together.

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post #13 of 16 (permalink) Old 07-08-2019, 11:35 AM
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Sometimes if your PVC valve is clogged and you have to much crank case pressure will force your oil dipstick up a little and your have some oil blowing our of that too.

You could drill holes in the top of the oil pan to relieve the pressure. JK. Don't do that. Reminds me of the brake guy at sears who told me to spay WD40 on my rotors because my brakes squealed with new pads they just installed. I don't think he was just kidding.
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post #14 of 16 (permalink) Old 07-08-2019, 12:07 PM
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Tough news, but.....

Quote:
Originally Posted by Iceotron View Post
Quick update, I installed the above and then it got worse, much worse. Compression check found that cylinder 7 had 0 and cylinder 4 had 30. The rest were between 120 and 130. I stopped diagnosis there and pulled the motor on Saturday. Now I need to find time to bring it to the builder. 543 miles since he built it. I'll update again once I get it there and we tear it down together.
...think how spirited your driving will be when you get 8 cylinders working instead of just 6. Hope the builder you referenced isn't the one you had previous issues with...

Get off my back, get out of my pocket....

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post #15 of 16 (permalink) Old 07-08-2019, 12:08 PM Thread Starter
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...think how spirited your driving will be when you get 8 cylinders working instead of just 6. Hope the builder you referenced isn't the one you had previous issues with...

The one and the same, kinda stuck to his hip at this point considering the money already invested and spent.

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