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Discussion Starter #1 (Edited)
After chasing a small leak for months, I can't really say I found the source, but I did just come back from a ride and find a puddle of oil on top of my block just behind the intake manifold. Any ideas where it could be coming from to puddle up there?????? I did find some in the recessed trim of the valve cover. Possibly through the breather? The intake shows no signs of oil. Thanks!!!--Mike
 

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FFCobra Captain
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Chasing oil leaks suck!

There is a gasket that goes under the intake along the back of the manifold.

How about the back corners of the valve cover gaskets? Maybe a tiny leak that only seeps oil in turns?

The oil on top of the valve cover is most likely from the breather, but not sure it would make it to the top of the block in back and puddle up there.
 

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Discussion Starter #3
Checked the manifold gasket at the rear... nothing there at the joint. Will have to check it again tomorrow.
 

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Mike,
I know you said that you checked the gasket at the rear of the intake but that is one of the classic SBF leak points. Many, myself included, use a heavy bead of sealer such as Permatex Right Stuff rather than the cork or neoprene gasket. Same at the front.

Good luck with it,
Jeff
 

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I know this isn't exactly the best way to fix it but....get a can of brake clean and hose down the manifold to block joint 3-4 times letting it dry completely each time. Get your favorite sealer (I like Permatex Ultra Grey because it is a little thicker than black or blue) put a small glob on your finger and work it into the joint. Be sure to go all the way across and fill in the ends of the joint. Let it set up overnight. I did that once in a situation where I just didn't have the time to pull it apart and do it correctly, and it stayed sealed for over a year until I had another reason to pull the intake.
 

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Discussion Starter #6 (Edited)
I am pretty sure it's probably from the breather. Working it's way out the breather, running towards the back of the valve cover and down to the block. I plan on taking a ride today along the same route as yesterday. I will take some paper towels and wrap the shaft of the oil breathers. This will still allow air flow, and will also allow me to check the paper towels after the ride to see if they have picked up any exhausting oil. If they turn out dry, I will look elsewhere. The intake was recently pulled and reinstalled by a shop and it seems to be sealed quite well. Can actually see the grey sealant that was squeezed out while it was snugged down.
 

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Is the baffle under the breather in place and un-molested? Is your PCV valve connected to a strong manifold vacuum source? That's all I've got. Good luck.
Frank
 

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Discussion Starter #8
Frank... No PCV at all. Just breathers in both valve covers.
 

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Mike,
It appears that there is an issue with mist/splash that may be exacerbated by crankcase pressure. I'm not saying this is the for sure cure but I would consider adding a good PCV valve from the passenger side breather opening to the base of the carb. Just something to think about. And the baffles are in place under the breathers, correct?
Frank
 

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Discussion Starter #10
Thanks Frank. I do have both baffles in place. I did also notice that every time I take the car out, the top of the dipstick pops off the dipstick tube. Should I be worried enough to do compression and leak down tests??? Car runs great otherwise.
 

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That indicates that the crankcase is being pressurized. How old are the breathers? Any chance they are partially clogged?
 

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Mike, I wouldn't worry about that, mine pops up a little bit too so no big deal. I think putting paper towel under the breathers to confirm that is the source is a good plan. Let's see what that shows.
Also, you have a good sized high output engine that is going to generate a lot of internal pressure when you start pushing it which can contribute to this condition. Not to dismiss your concerns but I have often seen breathers on HiPo engines wearing a garter to catch the oil mist. FWIW
Frank
 

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Discussion Starter #13
Sorry Craig... the breathers are 18 yrs old and original from the start of the build. Only 600 road miles, but lots of idling time over the years.
 

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I thought I had problems with my breather too. Turns out I had a hairline crack in my valve cover, virtually invisible to the eye. It took me three years to discover it. Sealed it up on the outside with a dab of J.B.

As far as the oil on the back of the block, are you 100% sure it's not residual gas from the carb? I once mistook residual gas (thick) for leaking oil.

I need to clean up around the manifiold a few times a year.

:icon23:
 

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Found it . . .

Quote: "No PCV at all. Just breathers in both valve covers."

IF you don't have some type of "draft tube" (very old school design) on your engine, and only breathers installed, you're going to get blow-by from the engine (and dip-stick pop-out) from the pressure that develops during hard driving - ask ANY old guy that has worked on engines from the 40's thru early 60's.

Engines used to come equipped with a "Draft Tube" at the rear of the manifold with its end down below the car, to create a [slight] vacuum, designed to evacuate the crankcase. Breathers are to allow fresh air in to compensate for that vacuum, allowing fresh air flow.

I'd be willing to bet that if you plug off your breathers completely, you'll blow the dip stick every time and your oil leak will transfer to the dipstick area . . .

Get a PCV system installed. Configure your PCV to your engine size. You could start with a factory 351 PVC and go [up] from there if needed.

Doc :beerchug:
 

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I had the same symptoms with oil filling the valve cover recess. It was the breather where it connected to the hose.
I had the hose going from the breather to the air cleaner without a PCV valve.

Rigged up a 302 PCV valve to a breather (not going to the intake now).

I'm still getting some pressure in the crank case so will vent the other side as well.
From some research it looks like I should run both vents to an oil collector can with a breather on the top.
 

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Discussion Starter #17
Update:
I installed a PCV valve. Pass side pcv with 3/8" hose to fitech vacuum. Driver side cloased breather cap with 1/2" hose to bottom if air cleaner housing.
The leak finding it's way to the top of the block is gone and the dipstick did not lift off the tube. I do still have a leak off the bell housing after shutting down. The rim of the oil pan gasket is wet on the driver's side, so need to investigate more. I'm thinking it's either the oil pan gasket or leaking from the timing cover and working it's way back along the rim of the pan.
 

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Mine leaked at the back of the intake after a few years. I was able to cinch all the bolts up 1/3 turn of so and it's stopped.

Check all your intake bolts.

Greg
 

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Mike,
You're closing in on it. The oil pan gasket will do exactly as you describe with an accumulated leak down the face of the BH plate. Makes you think it's the rear main seal which it rarely is. If you elect to attack the pan you have two choices. The full monty replacing the gasket and re-sealing the pan or a half monty leaving the existing gasket in place and sealing the pan. In either instance you'll want to apply a 1/4" bead of RTV Blue to the pan rails, sides only, fully encircling each bolt hole. Wait 20 minutes and bolt it up. Then let it sit overnight. I know gasket instructions say to leave it dry but ignore that. That's why the pans leak.
Frank
 

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New engine + stroker + high HP+ no PCV = dipstick to the moon.

I see that you have added a PCV. You will always have a filthy engine with open breathers. I have a PCV valve on one side and a Moroso oil separator on the other. I also HIGHLY recommend a Lokar locking dipstick. I blew my dipstick out at 6000 rpms and there was so much smoke I thought I blew my engine. I also oiled down the car behind me. It will calm down when the rings seat but not all the way.
 
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