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High Oil pressure causing leaks in 351W

kat

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Jul 22, 2015
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Bristol
Have a crate engine 351 that has a few thousand miles on it, and I cant stop oil leaks, especially around valve cover gaskets. At idle according to my gouge in dash she's running about 80#. I have new aftermarket aluminum valve covers, I've tried cork gaskets and rubber. Getting a new oil pressure sensor extension that comes from block since it feels a little loose. I've put thread tape on it but still doesn't help. Now its oily around my PCV valve which I'm gonna replace that to.
But mainly leaking around valve cover. Anyone recommend a GOOD gasket? Or tabs that go around the valve cover bolts? If so what brand.
 

Timmy390

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Conway, AR
Might I suggest getting a mechanical gauge and verify your real pressure. The in-dash gages can be WAY off. That said 80 at cold idle is a touch high but not crazy. My W is 60 at cold idle and 40-45 when hot on mechanical gauge. My 2500HD is 90 cold idle.....I'm told my Shelby is over 100 😮 I'm afraid to look.

Valve covers leaking,,,,,have you checked the mounting flanges on the valve covers? Often owners will over tighten them thinking tighter is better and it will bend the flanges causing more of a leak than they were trying to stop. I use Permatex 80633 Thread Sealant in every bolt that oil can week around the threads. Seems to work well. Don't all the oil pressure sensor extension that comes from block leak? LOL The one on my Mach 1 is leaking well weeping. I think I used tape on it back 15 years ago. Time for a redo with sealant.

Tim
 

DirtDonk

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What weight oil are you using kat? When I used 20w/50 my cold pressure was 70-75 and my hot pressure was 45-50. Never went below 40lbs even after a long high-speed freeway jaunt on a 100 degree day.
Oil pressure alone does not cause leaks in most of the areas you are describing. Too much volume might contribute, as would partially plugged oil return passages.
Oil pressure might cause excess vapors to collect up at the PCV area, but a poor baffle design could do it too. What valve covers and what oil fill cap design are you using?

When I got my Bronco (it was approx. 5 years old at the time) it already had a round steel tube in place of the leak-prone (and breakage prone) hex shaped aluminum thingy. No real leaks to report over the years. Maybe a seepage or two in a couple of decades, but nothing worth complaining about.
Too bad I don't think I took any pictures of it and I'm sure I sold it along with the engine. Would like to see how the end was done, but if memory serves, it was just a cast fitting with a 45 degree angle and threaded at both ends.
Pipe went into one end and the sending unit in the other.

Paul
 

bulletpruf

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Have a crate engine 351 that has a few thousand miles on it, and I cant stop oil leaks, especially around valve cover gaskets. At idle according to my gouge in dash she's running about 80#. I have new aftermarket aluminum valve covers, I've tried cork gaskets and rubber. Getting a new oil pressure sensor extension that comes from block since it feels a little loose. I've put thread tape on it but still doesn't help. Now its oily around my PCV valve which I'm gonna replace that to.
But mainly leaking around valve cover. Anyone recommend a GOOD gasket? Or tabs that go around the valve cover bolts? If so what brand.

I sure hope that's 80 psi at idle when cold. If it's 80 psi at idle when hot, I suspect your gauge is inaccurate.
 

DirtDonk

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With aftermarket valve covers, you might not ever completely get rid of the oil buildup around the PCV valve fittings. They are notorious for having minimal baffling to keep the oil at bay.

As said too, hopefully the PCV is connected properly and working.
Which PCV valve did you go with? Do they include one with the engine? Or does it come with just breathers?

Paul
 

Broncobowsher

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The oil behind the valve covers is NOT pressurized. The oil pressure extension has access to pressurized oil. The only other place where oil pressure could possibly touch a gasket is the front of the oil pan. That would be the oil pump spraying inside the engine, and that is almost never an issue.

As stated, the factory gauge is well known for being wildly inaccurate.

Aftermarket valve cover, well known for leaks as well. But oil pressure has nothing to do with valve cover leaks. All the pressurized oil galleys are in the blocks, none are in the heads.
 

Jarrett h

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May 24, 2020
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Loc.
Le Claire, IA
The oil behind the valve covers is NOT pressurized. The oil pressure extension has access to pressurized oil. The only other place where oil pressure could possibly touch a gasket is the front of the oil pan. That would be the oil pump spraying inside the engine, and that is almost never an issue.

As stated, the factory gauge is well known for being wildly inaccurate.

Aftermarket valve cover, well known for leaks as well. But oil pressure has nothing to do with valve cover leaks. All the pressurized oil galleys are in the blocks, none are in the heads.
Agree for the most part, but most motors produce a small amount of blow-by (crankcase pressure) & oil collecting around the gaskets w/ some gas pressure not escaping the valve covers could cause leaks.

Also, without oil restricting pushrods, a high volume oil pump will push much more oil into the valve area.

Checking the boxes off. :p
 
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kat

kat

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Everyone brought up some good points that I didn't think of. One is the overfilling of oil. The engine is a 95 5.8L, it calls for 5/20 synthetic and that is what I have been running. The engine didn't come with a oil pan but after research I bought one that came out of a van along with the oil dipstick. I put 7 quarts in it, maybe too much?
The PCV valve 'rattles' when I shake it so I assume its good. There is just a little oil coming from around it on the passangers side and on the drivers side I have a filter which also has oil coming from it.
When my oil sending unit extender comes in Im going to put a gauge on it to see exactly what its got.
 

TX-ZACH

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You never know 100% with all the different dipsticks, oil pans etc. My ATK 351w with stock pan calls for 5.5qts. I tried 6 and it does some weird things to it. The WIX 51515 is a very large filter and constipated for that. Idles and runs different, starts different. At least mine seems to like a little less filled than over filled. I have even had some seeps on valve covers that are no longer with a bit less oil.
 

Broncobowsher

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Don't know of any normal 7-quart pans. If it is a fabbed pan with extra sump, it could be a 7-quart pan.
The typical fox mustang swap pan (hint, 2 drain plugs, one for each sump) is only a 5-quart pan.
The 80's truck pan is only 6 quarts.
Those numbers account for a quart in the filter (4 in the pan + 1 in the filter = 5 quart mustang pan)
 

DirtDonk

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When you added 7 quarts, what did the dipstick say?
What year van did the pan come from?
Measure from the flange to the deepest part of the sump and let us know what that is so we can compare to other known capacity pans.
And perhaps most important of all to the life of your engine, did you also get the matching oil pump pick up tube for the pan? If not, that could lead to other issues.

While some six cylinder engines and 460 V8’s used 7 quart pans, like the other have said I have also never heard of a 351 Windsor that had more than 6 quarts capacity.
But I’m not a van expert by any means, so they could exist.
The measurements, part numbers on the dipstick and the pan if you have them, and a measurement might tell us the tale.

In the meantime, I would take a quart out perhaps. Maybe more.
With the proper pan and pickup tube our engines can run at normal pressures and volumes at lower RPM with as little as 2 quarts of oil in the pan.
I wouldn’t ever do that on purpose, but I know from personal experience that that is the case.

In your case, however, I would not remove more than 1 quart until you are sure that the pick up tube matches the pan.
And frankly, if it doesn’t match the pan, then there’s nothing else I would experiment with until you get a matching tube.
 
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kat

kat

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The oil pick up matches the pan but can't remember what year the pan came off of. I do remember measuring the oil pick up versus the bottom of pan so Im good on that end.
I failed to mention that every oil change I put a quart of Lucas oil treatment in along with 6 quarts of oil (7 quarts). The dipstick reads full when warmed up with 7 quarts in it. I'm due for an oil change soon, so I'll put 5 quarts in plus my oil treatment and see how that goes. Its a stock ford pan. This is the best pic I could get.

 

bmc69

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We ran 100-110 psi pressure at speed in the dry-sumped 429 in our offroad racer. No leaks. As has already been discussed above, internal engine oil pressure is not related to external oil leaks.
Oh..and teflon tape should never see an engine fitting. Use a good Loctite HP thread sealing compound.
 
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kat

kat

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We ran 100-110 psi pressure at speed in the dry-sumped 429 in our offroad racer. No leaks. As has already been discussed above, internal engine oil pressure is not related to external oil leaks.
Oh..and teflon tape should never see an engine fitting. Use a good Loctite HP thread sealing compound.
I do have thread tape on my oil pressure sensor/extension but will look into the thread sealer thanks.
 

bmc69

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oh..and why are you running a quart of Lucas??? That's only for "nearly dead" very loose engines and will actually contribute to the premature failure of an otherwise healthy engine! 1) That could easily explain your high oil pressure reading and 2) that high reading is a very false "positive"...high oil pressure at the pump outlet does not equate to high flow at the extremities of the oil distribution system. The opposite is, in fact, too often the case.
 
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kat

kat

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oh..and why are you running a quart of Lucas??? That's only for "nearly dead" very loose engines and will actually contribute to the premature failure of an otherwise healthy engine! 1) That could easily explain your high oil pressure reading and 2) that high reading is a very false "positive"...high oil pressure at the pump outlet does not equate to high flow at the extremities of the oil distribution system. The opposite is, in fact, too often the case.
I put Lucas in everything I have driven for decades. And back in the 80s I put STP in every oil change. My 260k F150 that I put oil treatment in since new would disagree with you. But I do agree that the oil gauge in dash is probably not correct since hardly anything is correct in my dash cluster.
 

DirtDonk

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And you never add a quart of additive on top of the filled to capacity crank case.
If you must add something, you are supposed to use less oil. Filling it to the normal full level only after everything is in there.
Not before.
 
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kat

kat

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And you never add a quart of additive on top of the filled to capacity crank case.
If you must add something, you are supposed to use less oil. Filling it to the normal full level only after everything is in there.
Not before.
I get your point, but me thinking that I have a 7 quart pan, I would put one quart of treatment and 6 quarts of oil. Maybe I'm not explaining myself very well.
 
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