Blow By... Front main blown again.

DMAX497

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Sep 27, 2012
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Okay so this is going to be a novel to get caught up to speed. I will do my best with the grammer. I am a college drop out and work in the car business. LOL:roflmao:

Have a built motor in my LBZ. Carrillos, MAHLE forged with reliefs,bored .20 over, girdle, oring block, LSM stage 3 AF cam, etc...

Last year when the motor was built; CP forged pistons were put into the truck.

The motor hazed bad out of both PCVs... Very loose... The truck then started to push oil from the passenger and driver side with a single S400. The truck was then upgraded to a S510 w/104 bill comp wheel under s475 compounds. The oil started to really puke out at this point. So much to the fact that we would have to put an oil tray underneath the pcv every time I would dyno the truck as 1-2 quarts would come out.

Fast forward after trying to swap the baffle etc on the valve cover. We put catch cans on the truck for a drag race event. One pass down the track and filled both catch cans up all the way and puked out the top. Probably 4-5 quarts at this point.

I then was so fed up with the piece of shit. The truck as picked up the next morning. Motor yanked out by a close friend. CP pistons were yanked out. Machinist inspected the block ( maybe 400 miles on the motor at this point ). And said not to run a quick bore hone in the motor as everything looked perfect still. Mahle forged pistons were put in. I have NO oil out of the drivers side PCV. Dry as can be! I took off the catch can and now is sitting on the frame rail for drivers side. I put the catch can on the frame rail for the passenger side. The motor still pukes every time I go down the 1/4 mile. Three passes equate to 28oz Gatorade bottle being full. Barely puts anything out on the dyno...

My rear main and front main were leaking. Had them both fixed. Not even 100 miles later I am at the track tonight and the front main is leaking again. And the passenger side is puking oil. Probably could have filled up another 28oz Gatorade bottle. The oil was worst the first pass and would get less and less after every pass with the MAHLE pistons...

Have heard problems of too much crank case pressure will blow the main seals out. My problem is I need a catch can so I do not oil down the track... But the catch can may not be letting the motor breathe. I see about 85lbs of boost...

My plan is to get the front main fixed again... Yank the catch can off. And take the truck to the engine builder. Do a compression test. Or yank the motor out and see what the f%&k is wrong.

Have read about MOPARKXRACER doing a vacuum pump... Thoughts?

Should I drill and tap more breathers? Bigger breather hose? I have a 5/8ths now...

Too much drive pressure? I do have a gate on the compound kit.

Change my oil out? I had Joe Gibbs in the truck... Now the motor has red line. Why would the oil push get less and less every pass? Do some oils when hot automize differently?

Need some ideas and thoughts...

Thank you in advance!
 
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CaptPhil

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Sep 10, 2011
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Oil probably pushes less after a few passes because the pistons are warming up and growing.

You should not be blowing that much oil though.

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NC-smokinlmm

<<<Future tuna killer
May 29, 2011
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Are you letting it get up to full temp before you run it? I know John Porterfield will go drive the piss out of his cummins before he hits the track or dyno and I meen like immediately before. I asked him why, and was told that the Pistons don't seat up the rings properly until it's up to "full temp" and kept there for a bit. I have no dea what Pistons he was running though. I'm sure they were top of the line since he is a part of the Scheid rail program.
 

DMAX497

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They are brand new MAHLE rings and Pistons.

I will ask my buddy what the gaps and ptw is.

I am not running the truck to full temp because don't want the truck heat soaked for the track. Get coolant temp to about 180 before running.
 
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x MadMAX DIESEL

<<<< No Horsepower
Dec 30, 2008
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They probably didn't use a torque plate and that machinist said it looks fine because it looks fine without a plate on it only lol


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DMAX497

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They probably didn't use a torque plate and that machinist said it looks fine because it looks fine without a plate on it only lol


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I'm pretty sure they do that... I'll ask again this week to verify. Motors are sim tested etc.

Should I drill and tap more breathers in the valve covers?

Run the breathers into the exhaust to pull the pressure out?
 

DIESELMAFIAPER.LB7

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They probably didn't use a torque plate and that machinist said it looks fine because it looks fine without a plate on it only lol


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Mine wasn't torque plate bored or honed. Though I have cast pistons but still zero issues like this. Know a forged piston motor with now 60k miles on it not burning oil or spitting oil that wasn't either
 

TheBac

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Apr 19, 2008
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I'm pretty sure they do that... I'll ask again this week to verify. Motors are sim tested etc.

Should I drill and tap more breathers in the valve covers?

Run the breathers into the exhaust to pull the pressure out?

You need to figure out whats causing the excessive pressure first. More breathers doesnt fix the main issue.

I would do as Blackmax said and do a compression test. That'll at least eliminate some things.
 

malibu795

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Apr 28, 2007
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Make sure the breathers are flowing.. I've popped a front main when a breather tube collapsed.... more HP means more blow by.. I built a tight engine. And I have blow by especially under load..
 

PureHybrid

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Feb 15, 2012
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With only 400mi on it? I say yes.

Cylinders aren't sealing up, 5/8 hose tapped into the valve covers should be gods plenty to let it breath. Either its honed wrong (should've been rehoned when rings were changed) or they never seated.

Piston clearance could be a factor but it would have to be double what it needs to be, to puke that bad in one pass.
 

DMAX497

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Sep 27, 2012
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Compression test will be done this week on motor.

What are the causes of the high crank case pressure? My breather tubes are opened and breathing just fine out of factory pcv holes in valve cover. Have billet plugs on them. Then the hose goes on them...

Your saying I should dump the redline out of it?

What oil is everyone else running?

There was about 400 miles on the cp Pistons. And now there is 350 with the MAHLE...
 

CaptPhil

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High crankcase pressure is caused primarily by combustion pressure leaking past the rings. Rings are never going to seal up the cylinder 100% but should not blow that much. You should do a leakdown test. Compression test won't tell you the whole story.

I doubt oil is your problem.

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DMAX497

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Leak down test first... Hopefully will have something Thursday.

What % should I look for to be, "out of tolerance". On the leak down test being done.
 
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LBZ

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I'd get concerned about anything over 25-30%

I wonder if 400 miles just isn't enough to seat the rings? Maybe needs a few hundred miles towing a few thousand pound trailer to help them seat?

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