Thoughts on a leaky engine - Team Camaro Tech
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post #1 of 19 (permalink) Old May 29th, 15, 11:49 AM Thread Starter
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Thoughts on a leaky engine

Please see my post "Protecting a New Aluminum Intake" for a thread with great responses leading up to this.

This is the second time that I am replacing the intake manifold gaskets. I've had leaks from areas that to me just don't make sense. A few observations that I'm not sure are relevent, so I'm gonna throw them out there and will appreciate any feedback.

The cold engine oil pressure is 65-70 psi. Is this high? When the engine is at operating temp, it's settles in about 22-25 psi at idle and 25-40 around town and cruise.

I have a PCV located in the passenger side valve cover. There is palpable
vacuum if you pull the valve from the cover. Located on the drivers side is an oil breather. There is always a little "blow by" exiting from it and an oily residue on the cover around it. I'm probably wrong, but I would think that with vacuum on the opposite side, air would be drawn into the drivers side cover, not discharged from it.

Is there something I'm missing here? I'd hate to put it all back together only to find out it leaks again and it's due to something I neglected or did wrong. Thanks everyone!
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post #2 of 19 (permalink) Old May 29th, 15, 11:55 AM
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Re: Thoughts on a leaky engine

When it's cold it's on fast idle. That spins the oil pump faster and increases pressure.

as to the rest: I only have one valve cover...

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post #3 of 19 (permalink) Old May 29th, 15, 12:06 PM
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Re: Thoughts on a leaky engine

Take a straight edge to the intake to head mating surface. Might not be straight. Have your heads been angle-milled to increase compression? If a lot was milled off, some will need to milled off the intake to get it to set right. Check for carb mounting bolt holes drilled to deep and breaking thru. All threaded fittings good and tight? What are you using for gaskets on the front and back of the manifold?
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post #4 of 19 (permalink) Old May 29th, 15, 12:59 PM Thread Starter
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I purchased the heads new when I built the engine back in 2007. As far as the intake goes, it was a used Weiand Stealth that I don't know what the history was of it, or if anything was done to it. I'm replacing it with a new one. As far as the oil pressure goes when the engine is cold, the higher pressure is more a function of increased viscosity then engine rpm. Just not sure if 65-70 is way to high, and whether there is something wrong with my PCV configuration or the functioning of it?
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post #5 of 19 (permalink) Old May 29th, 15, 01:02 PM Thread Starter
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The gaskets are Fel Pro, with the front and rear omitted and Right Stuff sealent being used this time. Previous was the black Permatex RTV.
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post #6 of 19 (permalink) Old May 29th, 15, 01:32 PM
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Re: Thoughts on a leaky engine

Johnny, when I first fire up my SBC 406, my oil pressure is the same as yours, once it comes down off of high idle it is a few pounds less, ten or fifteen minutes of driving brings it down to about 35-40 psi while just cruising with engine rpm's in the 1,500 to 2,500 rpm range. My valve covers stay pretty clean on both the PCV and breather sides. I run Valvoline VR1 10w30 conventional oil but there is one thing different between how you described your setup and mine. My PCV valve is in the drivers side valve cover and my breather is in the passenger side valve cover with a hose that connects to the nipple on the underside of the air cleaner housing. This is the way these engines were plumbed from the factory, I don't know if it makes a difference, some say it does, others say it doesn't. You could always try swapping your valve covers (or just the grommets in the covers if the holes in the covers are they same size) so that it is plumbed as it was originally from the factory and see if that makes a difference?

Only other possibilities are too much blow by so the breather/PCV system can't adequately handle it or the PCV valve does not have enough suction due to a bad PCV valve, incorrect PCV valve, or not enough vacuum which would cause a similar result as an incorrect PCV valve. GM also made a hollow PCV valve in later years to combat high oil consumption that might be worth a try, it doesn't have a spring and plunger valve and instead has a 1/8" diameter hole (or close to 1/8") to allow a continuous flow of crankcase vapors, thus evacuating the crankcase better in some situations.

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post #7 of 19 (permalink) Old May 29th, 15, 02:07 PM Thread Starter
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Re: Thoughts on a leaky engine

Interesting Scott and maybe a little reassuring that you have similar pressures. Ill switch covers. Ill try anything. I've been using the vacuum right off the manifold. By the way, I love your car, absolutely gorgeous!

69 Camaro convt. Metallic grey, Blueprint Engines roller 383 stroker 445hp/465tq. Edelbrock Air Gap intake. Holley Terminator EFI. Hooker stainless headers. Tremec TKO-600 5 speed, 3.55 posi rear, Vintage Air, March Performance, TMI Interiors
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post #8 of 19 (permalink) Old May 29th, 15, 03:03 PM
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Re: Thoughts on a leaky engine

If anything I'd say my oil pressure runs higher than yours, especially when at operating temperature. Yes either swap covers or the grommets and yes, PCV should have full time manifold vacuum. Make sure your PCV valve isn't gunked up and/or clogged, if you shake it can you feel the valve move inside it?

What is your manifold vacuum at idle?

Thanks for the compliment on my car, I love it too.

69 Camaro Z/28 RS, original Azure Turquoise, M21 & 3.73 12-bolt posi. NOM 406ci, AFR 210 heads, Straub hyd. roller cam & Dynatech 1-3/4" > 1-7/8" headers, QuickFuel 750 Annular. Photos at:
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post #9 of 19 (permalink) Old May 29th, 15, 04:46 PM Thread Starter
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Hi Scott the compliment is well deserved your car is gorgeous! I'd love to hear about the 406 sometime.The manifold vacuum at idle is 13 1/2 in Hg. The PCV appears to be working as I removed it while the engine is running and there is plenty of vacuum. I can't see were switching sides for the PCV will do anything but I'm going to do it anyway. What the hell, it's a quick easy thing to do. Maybe there is something I'm not aware of. All I know is that I've had lots of gasket failures.
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post #10 of 19 (permalink) Old May 29th, 15, 04:56 PM
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Re: Thoughts on a leaky engine

Scott has posted basicaly say the same as I would have...
My pressures are basically the same ball parl
my oil is std 20/40 for our local environment
The PVC goes to the bottom of the air cleaner.. the other side goes to manifold vaccuum

Which side goes where.. not sure off hand.. think the PVC is passenger side(??) which side is best has something to do with crank rotation from memory, thu unless running high rpms , it should not make any difference...

Quote:
Only other possibilities are too much blow by so the breather/PCV system can't adequately handle it or the PCV valve does not have enough suction due to a bad PCV valve, incorrect PCV valve, or not enough vacuum which would cause a similar result as an incorrect PCV valve
The PVC should be matched to the engine vaccuum characteristics... go thru some old posts on the subject....
If If u remove the oil fill cap, engine running...put your hand over the hole.. u should feel little or no pressure..
If u block off the Vaccuum to the PVC valve.. u should have a little/ slight pulsing/ blow by with your hand over the oil filler hole.
If excessive then u may have an issue with rings, or rings not bedded in....
A quick check/ indicator is mark the top of the sparkplug in the engine.. pull them out.. u know which way up they where.... blacking/ sooting on the bottom a ring issue... blacking on the top a valve seal / guide issue.

Quote:
Make sure your PCV valve isn't gunked up and/or clogged, if you shake it can you feel the valve move inside it?
This screws up tuning, engine efficiency... of ANYTHING in an engine that gets over looked is a clean functioning PVC valve.. even if rattles, take it out, and rinse well in a bowel of kero/ parrafin...
Thu an engine that has regular oil changes etc, a PVC valve runs fine for decades...and they last 100s of K miles plus.

My Spelling is not incorrect...it is creative

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post #11 of 19 (permalink) Old May 29th, 15, 10:21 PM
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Wink Re: Thoughts on a leaky engine

Quote:
Originally Posted by Steptoe View Post
... The PVC goes to the bottom of the air cleaner.. the other side goes to manifold vaccuum
...
Other way around there Steps

The PVC is plumbed from the valve to the base of the carb - or the "manifold" vacuum source.
The clean air intake can be via a filtered breather on the valve cover, in the oil fill tube if so equipped, or plumbed from the 'clean' side of the air filter housing to the valve cover of the engine.

GM tended to install the PCV in the 'Drivers' side valve cover and the crankcase clean air supply into the 'passenger' side cover.
This was to counteract the oil windaging characteristics of the vapors due to engine crank rotation.
Oil and vapors tend to accumulate on the passenger side vs. the driver side valve cover areas. Drainback is always inhibited more on the passenger side head ...
But if a system is properly sized, correct oil separating devices are used and your installation is correct, a properly functioning system can be fabricated using either cover and even the cam valley for the PCV pick up point.

A properly operating system should deliver 'Full' "manifold" vacuum to the PCV valve at idle and vacuum signal will diminish as throttle is opened until engine reaches cruise, at which time the vacuum signal will once again reach or exceed idle vacuum depending on load and throttle position.
The PCV valve will modulate the flow of vapors extracted from the crankcase dependent on this varied vacuum signal and keep pressure from building in the crankcase during the cyclic rpm's of a given driving cycle.
To 'weak' of a valve can lead to excessive crankcase pressures and result in excess windaging of oil vapors from openings and gasket interfaces of the engine.
To 'Stong' of a valve can lead to excess oil consumption via oil vapors sucked into the intake and also excess oil sucked past the ring lands into chamber - either of these is often seen as white smoke from the exhaust during hard throttle applications.

As stated, PCV Valves are specified by the pintle vacuum actuation values and are specific to a given engine type or state of tune.
If you are having issues it is best to find the recommended valve for your original engine configuration and then tune up or down on that spec. if needed to correct a given issue.

Hope some of that helps

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Last edited by Vintage 68; May 29th, 15 at 10:32 PM.
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post #12 of 19 (permalink) Old May 29th, 15, 11:24 PM
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Re: Thoughts on a leaky engine

Quote:
Originally Posted by Steptoe View Post
... The PVC goes to the bottom of the air cleaner.. the other side goes to manifold vaccuum
...
Other way around there Steps
yep my early morning expresso hadnt kicked in lol

My Spelling is not incorrect...it is creative

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post #13 of 19 (permalink) Old May 30th, 15, 04:23 AM
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Re: Thoughts on a leaky engine

One more item to verify is that each valve cover has a baffle directly under the grommet holes for both the PCV valve and the breather cap?

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post #14 of 19 (permalink) Old May 30th, 15, 02:59 PM
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Thumbs up Re: Thoughts on a leaky engine

Quote:
Originally Posted by Steptoe View Post
yep my early morning expresso hadnt kicked in lol
I think my 'adult beverage' hadn't quite kicked in yet, or I probably wouldn't have noticed it ...
I love this other side of the world time zone stuff, woke more than one person up over the years when I was working on your side of the globe

The important thing is the op gets accurate info to work from in all of these

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post #15 of 19 (permalink) Old May 30th, 15, 03:14 PM
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Re: Thoughts on a leaky engine

Interesting information about the PCV and its importance. Thanks!
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