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Discussion Starter · #1 ·
I have a 1968 Pontiac 400 with oil leak problems and I am looking for help/suggestions. This is the setup as I received it, and I have made no changes so far. Oil is leaking from the valve covers, primarily around the oil fill cap, the air inlet "snorkel", and a bit from the gaskets. The oil leaks a little through normal operation, but really spews out from the oil fill and snorkel when at high RPM. I want to change my setup but I am unsure what is the best route for new covers and proper plumbing.

There is a PCV valve in the valley pan and it is connected to the lower vacuum port of the carb. There are no other PCV hoses. The "snorkel" was added a long time ago (35-40 years) to help with oil spill issues, and it is supposed to allow air into the valve cover to force the oil down. There is a large ball bearing inside to regulate. I have never seen this before and would prefer to get rid of it.

What is the preferred setup? Completely closed valve covers with a breather to the valley pan or manifold? A breather on each valve cover? Install a proper PCV system as in a car? Are baffles in the valve covers recommended? I'm open to all suggestions. I've been researching for a while and still can't figure the right way to do this for the boat.


PCV from valley pan to carb vacuum
Vehicle Auto part Car Engine Fuel line

Driver side, oil fill
Engine Vehicle Auto part Motor vehicle Car

Passenger side, air inlet "snorkel"
Vehicle Engine Motor vehicle Auto part Car

Rear
Vehicle Car Motor vehicle Engine Auto part

Thank you for any input.
 

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First, the cause of crankcase pressure (includes valley and valve covers) is all relevant to the condition of your cylinders and ring seal. If your cylinder's leak down more than 15%, you will have some excess crankcase pressure. Without proper breathers, stuff will start leaking.
So, assuming your engine is in good shape....I would shitcan the PCV valve and that stupid snorkel (which is currently your only "breather"! Air is not coming in馃槀....it is going out that snorkel!
Buy some proper angle base tall valve cover breathers for those M/T valve covers and a new set of metal reinforced VC gaskets and you should be good to go! Jocko
 

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Discussion Starter · #3 ·
Thank you for the reply! It was very helpful. So you're saying there's no love for the giant snorkel??? I'm shocked! lol j/k

I'm sorting through the options for angled breathers and gaskets. Thanks again for the help!
 

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I'm not sure of the intended design function of the snorkel especially with the ball bearing function. It would seem to me that it would actually make the problem worse rather than help it. If I'm seeing the pictures correctly the opening of the snorkel is facing forward? If this is the case it would seem that at speed, air movement would pressurize the inlet and move the ball bearing to a closed position. This would not allow the crankcase pressure to vent which would then cause it to vent wherever it can and also cause the oil leaks, blow out the dipstick etc. Even if the ball bearing didn't close the air pressure at speed into the snorkel could cause the same problem, you want to vent the crankcase pressure, not increase it. Proper ventilation should help the majority of your leaks. I would ditch the pcv valve also just plug the areas it was attaching to. On the carb side I would make sure that port isn't needed or used for a signal to the carb for proper function. With good ventilation on the valve covers you should see a great improvement, I would also go with the quality valve cover gaskets as mentioned above. When functioning correctly you will still need to wipe on and around the breathers periodically as they will emit oil vapor which will collect on the breathers themselves and around their base(s).
 

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I'm not sure of the intended design function of the snorkel especially with the ball bearing function. It would seem to me that it would actually make the problem worse rather than help it. If I'm seeing the pictures correctly the opening of the snorkel is facing forward? If this is the case it would seem that at speed, air movement would pressurize the inlet and move the ball bearing to a closed position. This would not allow the crankcase pressure to vent which would then cause it to vent wherever it can and also cause the oil leaks, blow out the dipstick etc. Even if the ball bearing didn't close the air pressure at speed into the snorkel could cause the same problem, you want to vent the crankcase pressure, not increase it. Proper ventilation should help the majority of your leaks. I would ditch the pcv valve also just plug the areas it was attaching to. On the carb side I would make sure that port isn't needed or used for a signal to the carb for proper function. With good ventilation on the valve covers you should see a great improvement, I would also go with the quality valve cover gaskets as mentioned above. When functioning correctly you will still need to wipe on and around the breathers periodically as they will emit oil vapor which will collect on the breathers themselves and around their base(s).
I鈥檝e seen a similar setup, but the snorkel is pointing the wrong way. As mentioned above, it will build pressure pointed forward. The ball bearing sits on top and the tube is used to vent the valve cover and the rest of the engine thru vacuum. Some even ran a line to the header to assist in creating vacuum to open the ball bearing. Additionally If it has that, it shouldn鈥檛 have a PCV valve.
 

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Discussion Starter · #7 ·
I appreciate the feedback and suggestions. I will definitely try those gaskets, and work on finding some proper breathers that will work for me. I'd like to avoid buying new valve covers (I like the look of the M/T), but I don't think that will be an option since the holes have been drilled for the snorkel.

That's very interesting that someone has seen this snorkel setup before. That's the first I've had someone recognize it. Your description of how it should operate makes sense.
 

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Hey Trav,
Well, I think I'd definitely pull the M/Ts off and look underneath. Hopefully, the valve covers have their sheet metal breather hole baffles attached, although I'm not sure all M/T valve covers from back when had the posts cast into the undersides for mounting such. If they do, add baffles to the twist cap openings and replace the cap(s) with a twist-in breather on BOTH valve covers minimum. This is the most inexpensive first step. IF the PCV valve is operating correctly, there's no harm in keeping it, it would in fact help lower any crankcase pressures providing there is a path for outside air to enter the crankcase and complete the cycle. However most modified marine engines from back then omitted any smog controls and engines without any PCV valve are quite normal. Your ring sealing could be degrading, but there are lots of high mileage old cars out there that aren't spitting oil, even when they start burning oil. Butler Performance specializes in Pontiac high performance engines and parts ( You can Google Butler Performance ), and they may have a dedicated valley pan that has a breather as well.
I'd lose the "snorkel" and add breathers ( with baffles ) first, and see what you've got then, it may just be that simple.
The 400 engine , for Pontiac, is the best engine platform to use for any Pontiac enthusiast. It has the smaller main bearing size compared to the larger cu.in. Pontiacs, and it's generous crankcase will accommodate some big strokers with ease, should more cubes be in your crosshairs, so you're starting out with the one to use. Cool engines.
( p.s., my wife showed me your Yahoo message, sorry, I've been busy elsewhere for a while...鈥.yes, the boats are doing well. )
 

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Discussion Starter · #9 ·
Thanks for the reply Spike. Glad to hear from you!

I will check out the underside of the covers this weekend. I have some breathers coming in the mail, so I should be able to try everything soon. And thanks for the Butler Performance suggestion. I'll check them out.
 

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Spike nailed it. I couldn't get a good angle view on the engine, but if it tilts rearward at speed, I would use the earlier style pushrod cover , which has the PCV to the front. The Pontiac pushrod cover is an excellent air/oil separator--don't go aftermarket. I never saw the snorkel gizmo (50+ years Pontiac experience) but my guess is the open end would go to the air cleaner to provide a filtered air source for the crankcase breathing system. I would ditch it. SO-2 twist in breathers, retain the PCV, use a front PCV exit push rod cover if necessary. Perform a leak down test to get a snapshot of your engines health. BTW - Ram air pressure @ 150MPH is only 0.4 psi.
 
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