Intermittent crankcase pressure issues

Discussion in 'Small Block Mopar Engine' started by Deceus, Nov 10, 2018 at 11:49 AM.

  1. Deceus

    Deceus Well-Known Member

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    I'm getting crankcase pressure issues with my freshly rebuilt 318. I had this issue before and it ended up being from some bent exhaust pushrods that was caused by a lack of oiling since my rocker shafts were on wrong. I found the issue really early and didn't appear to do any real damage to the cam. The issue has kinda crept back but not as severe. I'm getting a little bit of oil in my valve cover breather and out the front of my intake.

    I have a PCV and tested to make sure it was functioning properly. I did a compression test and all cylinders were between 135-145. I took the valve covers off and made sure all the push rods were spinning freely so I don't think any of them got bent again. So now I'm out of ideas.

    I'm not getting an issues at idle or just driving around so I'm not sure the valves guides are the source of the problem. It seems to be an issue at high loads + high rpms so I'm thinking it may be another oiling related issue. I went with a high volume oil pump and a windage tray but stuck with a stock 4 qt oil pan. I'm think the issue might be the lack of volume and/or baffling in the pan but I'd like more input before I pull the trigger on anything.

    I did a hillclimb/cruise a month ago and that seemed to be the worst of it by far. During one of the steeper climbs there was enough oil coming from under the breather to leak onto the headers and cause a small amount of smoke under the hood.

    Am I on the right track here?
     
  2. Dubob

    Dubob Well-Known Member

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    Are the baffles in place in the valve covers for the breather and pcv ports? Where do you have the PCV plumbed in to? What weight oil, this may effect how fast it returns to the oil pan especially with high volume pump. If you are running a non stock breather (no hose to air filter housing) it’s very possible to have more blow by at higher rpm. With the throttle blades open further the vacuum in the intake moves more towards atmospheric pressure. This causes the PCV to draw less and that is the point the factory style breather with hose to air filter takes over.
     
  3. nm9stheham

    nm9stheham Well-Known Member

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    As above... more time at wider throttle openings, the PCV is less effective and you'll see more crankcase pressure.

    Having said that, the situation where poor ring seal shows up is under heavy throttle. That can come from bore wear or ring groove wear. Was this a fresh bore and new pistons?

    I would not expect this to be from an oil pressure issue. Lack of baffling in the pan on that hillclimb would more likely show up in oil starvation, but that is not related to crankcase pressure.
     
  4. Alaskan_TA

    Alaskan_TA Well-Known Member

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    Since you say the rebuild is fresh, it is possible that the rings have not fully seated yet.

    How many miles on the engine prior to the hill climb?

    What type of oil did you use for the break in & what is in it now?
     
  5. AJ/FormS

    AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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    IMO
    You need a deeper pan. And the oil needs to get back to the pan faster. Your HV pump is flooding the top end, and the crank is beating up on whatever comes down.
    You might have to either limit the oil to the top or swap out that HV pump..... or both
     
  6. Deceus

    Deceus Well-Known Member

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    Everything was brand new and freshly machined. It's right around 700 miles at the moment. I used Royal Purple break-in oil and that's what's still in it now. PCV and breather both are baffled but it's an aftermarket breather not hooked up to anything.
     
  7. nm9stheham

    nm9stheham Well-Known Member

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    Not computing..... I am trying to figure out how an HV pump can 'flood' anything more than a standard pump, if the pressure relief spring is at the same pressure setting? Once either pump gets to high enough RPM, the pressure limits per the spring, and the flow to the head limits. Not saying there is not oil setting in the heads, but changing the pump is not going to change that... unless you coincidentally go to the lower pressure relief spring.

    And maybe I am not seeing something..... I am not seeing how oil around the crank will raise crankcase pressure per se. Or is it just making the air in the crankcase more oil-filled, and thus making the symptoms more noticeable?
     
    Last edited: Nov 11, 2018 at 8:51 AM
  8. nm9stheham

    nm9stheham Well-Known Member

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    'Freshly machined' as in re-bored for new oversize pistons? Moly top ring set or ???? Chrome rings are long/difficult to seat... Got a ring set PN?
     
  9. AJ/FormS

    AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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    This is not an oil-pressure issue.
    IMO; It's a drainback issue at high rpm with the car not sitting level and maybe being tossed around from side to side. The HV pump moves a lotta oil and when that oil piles up in the valve covers it runs down to the back of the heads and piles up there waiting for it's turn to escape the heads. If the rear guide seals are not the tightest, oil will get into the chambers with attending smoking out the tailpipes. Now, when the oil finally makes it into the valley and down into the intermediate gear, that spinning oil-flinger fires it out sideways in every direction. Some of the oil makes it to the crank which also fires it out in every direction,vertically now,and aerating it in the process. And the oil-level in the pan is rapidly declining, because the oil is all in suspension getting the beating of it's life.And the piston motion is pushing that slug of aerated oil around like mating Wallruses..
    Now, the PCV doesn't function the same at hi-rpm/near zero vacuum as it does in hi-vacuum cruise mode, so it ain't doing much, except maybe venting aerated oil out of the one cover and into the intake. The breather is now pushing blowby out onto the valve cover, and it too may be overloaded and pumping oil.
    Yeah so maybe the rings ain't helping either; but blowby can't be eliminated, and a hill-climb is a sustained hi-rpm event, many times more strenuous than a drag-race.
    ________________
    I cured my rally-cross problems by cutting drainage channels in my soft aluminum heads, by drilling the valley pockets, by running just 5 quarts in my 7 qt roadrace pan, by re-engineering my breather system,and by disconnecting the pan E-vacs for the event..
    I already had the deep-pan and the fresh-broke-in Moly rings, with almost immeasurable Leak-down, and almost immeasurable Blowby on the gauge. And; I was running very high cranking cylinder pressure, about 11/1Scr and as I recall over 185psi.
    I left the HV pump on there, as I had previously drilled out all the passages to accommodate it; and I had no intention of loosing any more rods,lol; Cuz you know I don't always shift when the power peaks lol.Sometimes I stretch ...... it.............. out................ a .............. lil.........bit. I mean if it's still spinning or pulling and I'm winning and I just need another 50ft, what the heck is the difference! I'll loose less time stretching than shifting.

    >Actually, I don't think the engine has a problem at all. Other than a baffle/breather issue, and possibly a poor seal at the front of the intake.
    If it was mine,I would re-engineer those and then;
    I would plumb a lo-pressure gauge to the dipstick tube with a long hose and put the gauge where I could see it from the driver's seat. Then take it for a roadtest.
    If the gauge showed more than 4 psi, I would tear it all apart looking for the problem. That's HotRodding.
    But if less than 4psi,and it still had a problem, I would install a 7qt or more roadrace pan and run it a qt or two short of full.
    That's what I would do, er did.
     
    Last edited: Nov 11, 2018 at 11:04 AM
  10. nm9stheham

    nm9stheham Well-Known Member

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    Ain't trying to be contrary.... the HV pump CAN push 18-20% more oil than standard.... into an open system with no restrictions.... which an engine is not. Once the pressure relief limits the pressure, then the flow into the engine is not set by the pump's potential volume. It is set by the pressure at the back of the passenger side gallery (the main feed point to everything) and the pressure. Once either pump limits pressure at mid RPM's, then the flow is the same between the 2 unless the relief springs are different.

    I just don't want the OP to change oil pumps for no change.

    Drain-back is another matter and crank aeration. That may well be the issue. I just want to investigate the cylinder sealing simply as the OP's engine symptoms are classic for poor ring sealing.

    The suggested tests seem pretty darned good.
     
  11. DesertRat

    DesertRat I don't care it's all psychobabble rap to me. FABO Gold Member

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    I am saying PCV issues. With only 700 miles the engine is still seating everything. Stock PCV systems evacuate at idle and light cruise but under power all engines develop internal crankcase pressure unless provisions are made. (like yellow rose did on his race engine) With the current information available, I would look there to solve the problem. JMHO----------:)
     
  12. AJ/FormS

    AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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    I hear ya.
    But I'm going on the assumption that the two pumps operating at the same rpm and at the same pressure, the HV is pumping more oil. That is what I installed it for. That is why I drilled out all my passages, ported all the corners, and increased my clearances slightly, including extra lube to the top end in an effort to prevent galling my aluminum rockers, and,I use that extra lube up there to cool the springs. Cuz you know how hard I work them,lol.Of course that extra lube had to have an escape path back to the pan....and I didn't provide enough on the first assembly.
    I took that engine apart every winter for five in a row, to prevent or to solve issues. After the last one, it hasn't been apart since winter of 2004.

    I agree with your post 100%
     
  13. Deceus

    Deceus Well-Known Member

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    Rebored 30 over for KB167-030 pistons with these rings: Keith Black KB Performance Piston Ring Sets 3910BD8-030

    dJusDfR.jpg

    I did a leakdown test last winter and got a few weird readings on 2 cylinders. They'd read real low (20%) but spinning the engine back around to a second compression stroke and they'd read fine (90%+) so I'm definitely not ruling out some issues with rings sealing. I'd rather not pull the heads at this point just to double check though. I don't think it's just a bad seal at the front of the intake since it seems to be finding quite a few points to leak. My front and rear seals on the oil pan are usually damp with oil as well along with the base of my oil filter. There's got to be too much pressure in there I just can't recreate it in a manner that I can observe it.

    I was considering some kind of exhaust evac system but I felt like I was tackling a symptom of a bigger problem rather than addressing the problem itself. This is far from a radical engine so I wasn't really expecting many problems like this. This is my first engine build and break-in so it may be a little early to consider a bit of blowby a real issue. I'll probably pickup a Milodon road race oil pan in the short term if it'll work with my k-member and I've been eyeballing the new trickflow heads so I may get to do a complete teardown soonish anyways.
     
  14. Alaskan_TA

    Alaskan_TA Well-Known Member

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    Easy place to start - hook the breather up & take it for a drive.

    The breather is there for a reason.
     
  15. nm9stheham

    nm9stheham Well-Known Member

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    OK, tnx. Well those rings ought to break-in pretty easily and quickly with the moly faced tops. As far as still breaking in.... I am a bit dubious. I was cautious with my rally engines and drove them 100-200 miles when new with varying engine loading, and by the time they hit the 1st stage, they were solidly broken in. Used moly top rings and never had any big blowby issues. I'd get just a 'smidgen' of oil out of the open breathe hole in the valve cover. (4 cylinder, 4k to 8k RPM's.) You've put plenty of loading on the rings by now.

    And I agree that this does not sound like a simple seal issue.

    As for the leakdown, the test ought to be done with the engine rotated and then stopped so that the piston in the cylinder under test is on the upstroke, to simulate the ring positions on the power downstroke. That might explain the changes in the leakdown results.

    Rings installed with the 'dots' up? Top rings gapped per the KB instructions?
    Where is the PCV valve hooked up to? Sure it is directly into the intake? What kind of RPM range are you running?

    Going back to your #1 post, I am trying to think how the bent exhaust pushrods would cause these same symptoms....

    I'd seriously run the test with the low pressure gauge like AJ described. You can use a simple vacuum/fuel pump pressure gauge. That will give you some direct numbers on the crankcase pressure for evaluation. (You can tell if it is really gross blowby by putting you hand over the open breather hole at idle..... there ought to be very little or nothing blowing out. But that can be subjective.)

    BTW, that hill climb sounds fun... where was it?
     
  16. AJ/FormS

    AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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    Comments inside the quote
     
  17. Deceus

    Deceus Well-Known Member

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    The compression test was this weekend and the leak down was early this year, I've done both now. I know 20% is huge, not sure what was going on there but I was doing it right and getting good readings on the other cylinders. I got good readings on those cylinders as well when I spun the engine back around to the next compression stroke so I know it wasn't user error. It's almost like the rings (or something) was only sealing part of the time and could explain al ot but I don't think the engine would really be running all that well if 2 of my cylinders where letting 80% by even part of the time.
     
  18. Deceus

    Deceus Well-Known Member

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    33W leaving out of Harrisonburg towards WV


    The bent pushrods came from my rocker shaft being on the wrong way. This probably starved the valvetrain and caused the exhaust valves to stick and that was causing some issues with blowby.

    8B35oZT.jpg

    Bent Pushrods on a rebuilt 318
     
    Last edited: Nov 11, 2018 at 4:14 PM
  19. nm9stheham

    nm9stheham Well-Known Member

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    Ah... I see the problem... there is a big hole in your hood LOL. Too bad those guys ahead of you were so slow. I go faster up that road in my Mega Cab. (I live 1 county south.) And, you missed the turn-off to Reddish Knob... doggone, who is running this show !?

    All kidding aside, that type of run does not look like it should put much pressure in the crankcase. It is only a few seconds of throttle at any time. I'd sure like to see a pressure gauge reading when you are on it like that....hint, hint...
     
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    • Deceus

      Deceus Well-Known Member

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      yeah my hoodscoop came off the day before that drive. Some studs wiggled loose and I didn't have time to redo it.
       
    • AJ/FormS

      AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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      Just three or four straight ones? Hmmmmmmmmmm
      Yeah the video seems to show an easy exercise for a V8. There is no good reason for that workout to cause CC pressure issues.
       
    • Deceus

      Deceus Well-Known Member

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      Oh yeah something is definitely wrong for sure I just can't narrow it down and I'd rather not pull the engine this winter if I can help it. I might be able to pull the passenger side head and get a better look at everything without too much issue. I'd like to measure the pressure but I feel like it's just going to tell me what I already know.
       
    • AJ/FormS

      AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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      Well if you know it then you gotta pull it, and fix it before it blows the rear main seal out...... along with half your oil........ which will do a lotta damage in just a few seconds. Or if it pukes oil on the headers instead and the car catches fire, then you are looking at a really,really, bad day.
       
    • nm9stheham

      nm9stheham Well-Known Member

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      Yeah, but you might notice something that will give us a clue. It could be something like a bad PCV valve or setup. Data is your friend...
       
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