Crank Case Pressure oil leaks ?? Help - Team Camaro Tech
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post #1 of 24 (permalink) Old Mar 10th, 10, 06:35 PM Thread Starter
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Crank Case Pressure oil leaks ?? Help

Once again I come to you all who know way more than me. I have been chasing an oil leaks on my new BB 468 for a couple months. My leaks are not major but once I repair one it springs a small leak somewhere else. Do I have too much crank case pressure? I have a pcv valve (AC Delco for a 70 big block) on the pass side to the carb base and a K&N breather on the drivers side front. My leaks were coming from the valve cover gasket..fixed …a trickle from the rear of the manifold and from the corners of the oil pan..fixed…now I see drips from the rear seal area and the front of the pan. I am chasing my tail here and need some help. The motor runs strong and has about 400 miles on it. Do I need to wait for rings to seat? My oil looks kinds dirty to me already….I did a search for pcv and have read many different opinions on pvc location…etc My motor is nothing fancy with a mild cam. My vacuum is about 11 at idle if that helps at all. Is there any way to measure the crank case pressure? How can I relieve it if is an issue? Any help would be greatly appreciated..

Gary

67 RS Resto-Mod 468 5 spd TKO600 3.73 12 bolt (work in progress but finally on the road!)


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post #2 of 24 (permalink) Old Mar 11th, 10, 03:58 AM
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Re: Crank Case Pressure oil leaks ?? Help

You may need a PCV for a Z/28 or a 375 HP/396 CID since the manifold vacuum is low - PCV will have a weaker spring allowing it to open under less vacuum. However, the valve woul dbe open upon deceleration, max vacuum.

I haven't seen one in years, but there is/was a flowmeter device, 2 inch diameter gauge, one would place over the oil fill hole and it indicated either vacuum or pressure of the crankcase.

If crankcase is pressurizing, one would see oil at the filter on the valve cover much like seeing oil in the air cleaner base of an OE set-up.

An old shadetree trick is to remove oil fill cap and place hand over tube with engine running and after 30 seconds, one should feel a vacuum, if it was sucking/working.

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post #3 of 24 (permalink) Old Mar 11th, 10, 05:33 AM
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Re: Crank Case Pressure oil leaks ?? Help

I have a vac/pressure gauge, a little adapter in the pcv hold should show something. we can swap it when I pick it up the trans jack

Kevin


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post #4 of 24 (permalink) Old Mar 11th, 10, 01:55 PM Thread Starter
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Re: Crank Case Pressure oil leaks ?? Help

Thanks guys...

Everett...ant clue as to an AC Delco part # for that specific pcv for a 375 hp BB I figured that a 70 BB 454 was in that range. I'll try to search it up and see if i can find a part #

Thanks

PS Kev...got my tranny jack today...not too shabby!

Gary

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post #5 of 24 (permalink) Old Mar 11th, 10, 07:43 PM
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Re: Crank Case Pressure oil leaks ?? Help

Gary,
If you have a breather on one valve cover, that should eliminate most pressure. Having the pcv valve is just a plus and the engine should run fine without it. Dont forget that most engines up to the mid 60,s simply had breathers with no type of pcv system at all.

There is a blowby gauge available that you can put into one of the valve cover holes, then block the other one and actually measure blowby cfm at various rpms and under a load. I forget the exact numbers that are acceptable, they are on the instructions sheet in the gauge at the shop Pull the breather and the pcv valve and rev the engine up some and see if you can feel or see any smoke coming out of the valve covers. If you can feel air coming out, you probably have too much blowby

If you do have a blowby problem, the only way to solve it is to find out why the rings are not sealing and fix that problem. Modern rings should be pretty much seated on the engine stand if the cylinders were properly finished.

Bill Koustenis
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post #6 of 24 (permalink) Old Mar 11th, 10, 08:18 PM
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Re: Crank Case Pressure oil leaks ?? Help

736V is the one specified for '69 302 and the 375hp 327 Corvette low vacuum engines. I would not call 11" of vacuum at idle a mild cam but some who race might.

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post #7 of 24 (permalink) Old Mar 12th, 10, 08:26 PM Thread Starter
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Re: Crank Case Pressure oil leaks ?? Help

Thanks everyone for the info...I will check things out and get the pcv valve replaced again.

One more question: I have a 7 qt moroso oil pan and a high volume oil pump that is giving me around 75+ psi at startup idle and drops down after warmed up but usually in the 60's driving around locally. Maybe down in the 40's at idle when hot. Is there too much oil pressure that could be contributing to the oil leak? Thanks a bunch

Gary

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post #8 of 24 (permalink) Old Mar 21st, 10, 07:47 PM Thread Starter
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Re: Crank Case Pressure oil leaks ?? Help

Anyone have a part # for an ACDelco pcv for a 375 hp big block or a sb302? I tried my local parts counter but they couldnt find a valve other than just big block which is what I already have. According to above I may need a pcv from a lower vacumme motor. Steiner gave me a part # above but they didnt know what that # was. These guys are usually pretty good and not an Autozone or Pep Boys chain parts store. The showed a valve in Fram and in Standard but looked it up and it wasnt available anymore ???

Any info would be appreciated

Gary

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post #9 of 24 (permalink) Old Mar 22nd, 10, 04:03 AM
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Re: Crank Case Pressure oil leaks ?? Help

You might check the oil filter book at Pep Boys or other DIY and see about crossover part number. NAPA would be a good place. So would www.hemmings.com.

Higher oil pressure does make for more oil being thrown around, especially at the top end if the the block galleys have not been restricted to limit amount of oil to the top. The pressures you see are inline. I have the same set-up except I asked for 0.003" clearance rather than 0.002" and I get 20 PSI at hot idle and 50 PSI at 5K rpm.

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post #10 of 24 (permalink) Old Mar 22nd, 10, 06:54 PM
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Re: Crank Case Pressure oil leaks ?? Help

736 is a standard number (full number CV736V) and the one I have is a Purolator. If you ask for one for a '69 Camaro 5.0 liter 302 that number should come up at Advance or AutoZone. The Frams that I have seen are cheap plastic whereas the Purolators are metal.

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Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
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post #11 of 24 (permalink) Old Mar 22nd, 10, 08:33 PM
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Re: Crank Case Pressure oil leaks ?? Help

Youu might try a leak down test at TDC to see if their is a ring seal problem,

Here is a good link to look over on 454 that was not plate honed and was having some issues.
https://www.camaros.net/forums/showthread.php?t=58964
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post #12 of 24 (permalink) Old Mar 23rd, 10, 05:01 AM Thread Starter
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Re: Crank Case Pressure oil leaks ?? Help

Thanks Steiner

Quote:
Originally Posted by Steiner View Post
736 is a standard number (full number CV736V) and the one I have is a Purolator. If you ask for one for a '69 Camaro 5.0 liter 302 that number should come up at Advance or AutoZone. The Frams that I have seen are cheap plastic whereas the Purolators are metal.

Gary

67 RS Resto-Mod 468 5 spd TKO600 3.73 12 bolt (work in progress but finally on the road!)


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post #13 of 24 (permalink) Old Mar 23rd, 10, 05:03 AM Thread Starter
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Re: Crank Case Pressure oil leaks ?? Help

Thanks Carl...I did a leak test already and everything looked fine. Just checking everything. Its a dribble thats getting on my nerves.


Quote:
Originally Posted by CNC BLOCKS N/E View Post
Youu might try a leak down test at TDC to see if their is a ring seal problem,

Here is a good link to look over on 454 that was not plate honed and was having some issues.
https://www.camaros.net/forums/showthread.php?t=58964

Gary

67 RS Resto-Mod 468 5 spd TKO600 3.73 12 bolt (work in progress but finally on the road!)


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post #14 of 24 (permalink) Old Mar 23rd, 10, 05:23 AM
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Re: Crank Case Pressure oil leaks ?? Help

Gary,

Just my opinion ...... I think you are wasting your time looking at the pcv valve for an answer to your oil leak issues. If it was a crankcase pressure problem you would be puffing smoke from the breather or pushing the dipstick out of its tube under load. You should be able to remove the pcv valve completely and run 2 breathers and still not have an oil leak. How many race engines do you see with pcv systems on them ? Do they leak ?

Same with the high pressure pump .... it will not cause an oil leak except for at an oil galley plug that is not sealed correctly.

What you have is a leak ..... you need to find where the oil is leaking from and fix the problem. Simple as that.

Start out by buying a $5 bottle of leak detecting die at the parts store and a $6 UV light bulb from Wal Mart. Put the die in the oil, drive it a few miles than use the light to see where it is leaking from. You would be surprised at how far oil can run, or get blown around an engine before it decides to drip off. Your drip in the back could very well be from a valve cover gasket at the front of the engine. The die glows bright yellow and allows you to see exactly where the oil is coming from.

Forget about the PCV valve .... fix the leak.

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post #15 of 24 (permalink) Old Mar 23rd, 10, 07:00 AM
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Re: Crank Case Pressure oil leaks ?? Help

What kind and weight of oil are you using.Low viscosity synthetic oils are notirious for making it past the seals on older engines.This is why newer engines have such better gaskets systems.Center bolt valve covers,RTV in place of manifold seals,one piece pan gaskets with stiffening rails on the pan.Cast pans,valve covers and front covers.All these things were done to make the engines seal with modern near zero weight oils and high tempatures.Unless I have a vacum pump on a big block,there is always a little dampness or a little hanging drop of oil on the bottom of the engine somewhere,even with 20/50 weight.You can litterally chase leaks for so long that eventually you start making more leaks fixing the ones you already have.
So whats your oil weight/type?
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