I have some leaks around my Olds. Not like a running drip, but more like it has been sprayed/vaporized. Not a lot, but a little here and there, like around the pan, fuel pump boss (that is blocked of), the front seal and in the bilge. I'm pretty sure I have too much crankcase pressure. I don't have
any drain back mods done so I know I get too much oil in the valve covers if I stay in it too long. But with all the oil "mist" around the lower half of the motor and in the bilge I'm thinking too much crackcase pressure is pushing the gaskets and seals.
The motor runs good and was built 20 years ago, but only has maybe 40 hours. I want to run a leak down test because I'm curious if the rings were seated.
BBO 10:1 CR, 10 quart pan with 8 quarts oil. Mickey Thompson valve covers with tall Offenhauser breathers, not baffled, is the only ventilation,
no PCV. 

If the leak down checks out, I'm pretty sure it's a venting issue. My question is, if I put a breather on the oil fill tube, would that help?
I know a pan evac or puke tank would be better, I was just curious about this breather on the oil fill cap idea.
A breather like this:


edit- on the oil fill cap.

I just put a breather on my oil fill too. Hope it works.

I have a pretty much stock olds 455 in my boat. It has great compression on all cylinders with moroso breathers. I had a problem with oil filling the valve covers and spraying out of the right hand breather. This winter i installed external drains to the pan and it completely solved the problem. Just wanted to share.

The Oldsmobile oiling problems just don't and end with the drain backs that are attached to the heads and the engine oil pan.
 Many people do not read the complete article that was published years back in hot boat magazine. Those drainbacks are just the tip of the iceberg with regards to the oil drain back problem deals with the olds are known for.
When pulling the heads to put in the drain backs, I hope you guys addressed the center exhaust divider , if not you guys missed 50 horsepower. And I hope you guys got the drain backs, in the pan,in the right location to avoid the slosh from the crankshaft. So drain lines would even work right. And as the author even States if all the other oil issues are looked after those drain back lines would probably not be necessary at all. But no doubt there are good idea,just as all the other steps are as he mentioned.

Tim Jurincie (author) goes over extremely important item you got an Oldsmobile heads the stock hits. It's the filling of the exhaust crossover ports in the center two cylinders. Along with that goes the reporting and reshaping of those four Bowles under the valves. It gives the Oldsmobile a different idle characteristic and probably another 50 horsepower. Forgive me but I'm rambling. All Good Things to Remember when you're building an Oldsmobile for sure.

Just going with breathers


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I've used my old motor with no oil mods beside opening up drain back in heads, for 8 years . It doesn't mind running wide open throttle for a couple thousand feet then back off. I've stepped it up with new motor and she's a beast....
She sounds pissed off ! going to run it this weekend in Blythe ..


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The Oldsmobile oiling problems just don't and end with the drain backs that are attached to the heads and the engine oil pan.
 Many people do not read the complete article that was published years back in hot boat magazine. Those drainbacks are just the tip of the iceberg with regards to the oil drain back problem deals with the olds are known for.
When pulling the heads to put in the drain backs, I hope you guys addressed the center exhaust divider , if not you guys missed 50 horsepower. And I hope you guys got the drain backs, in the pan,in the right location to avoid the slosh from the crankshaft. So drain lines would even work right. And as the author even States if all the other oil issues are looked after those drain back lines would probably not be necessary at all. But no doubt there are good idea,just as all the other steps are as he mentioned.

Tim Jurincie (author) goes over extremely important item you got an Oldsmobile heads the stock hits. It's the filling of the exhaust crossover ports in the center two cylinders. Along with that goes the reporting and reshaping of those four Bowles under the valves. It gives the Oldsmobile a different idle characteristic and probably another 50 horsepower. Forgive me but I'm rambling. All Good Things to Remember when you're building an Oldsmobile for sure.

What do you in the right location on the pan? And I didn't even pull my heads just drilled em on the motor with the shop vac running ahaha. Maybe I just got lucky but I can stand on the throttle for over a minute now and not get the slightest mist as before 30 seconds of wot and I'd literally be pumping oil straight out of the valve covers


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** Or without pulling the heads?

How did you install external drain lines without taking the heads or the pan off your engine?

The motor was on the stand. I pulled the pan off and welded bungs on but I left the heads on the motor and drilled them on the stand. Adapted a 3/8 hose to the shop vac and shoved it down the oil galley and started drilling and tapping


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Ya I read that of course after I welded the bungs. One of them lined up in the right spot and the other was dead nuts lined up with a c rod. Oh well. Doesn't seem to bother it.


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Can anyone snap a picture of the correct placement on the pan?


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I got it thanks


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