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blow by out breather.. #3048748
06/07/22 09:54 PM
06/07/22 09:54 PM
Joined: Jul 2011
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wine country
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8urvette Offline OP
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wine country
Just got my Barracuda running again.
I replaced the cam with a smaller more streetable cam, it runs great. I also added a bunch of ring gap while I had the motor out . It now smokes some at idle out the breather, Which I expected when I added ring gap (plans for nitrous) but the issue is the valley pan leaks oil at high RPM. I think I am getting a significant amount of blowby at 5K + rpms. The question is, will a evac system running off the headers be beneficial and stop the pressure from causing an oil leak at the valley pan? Or do i need a vacuum pump at this point?

Re: blow by out breather.. [Re: 8urvette] #3048752
06/07/22 10:01 PM
06/07/22 10:01 PM
Joined: Aug 2003
Posts: 43,007
Bend,OR USA
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Cab_Burge Offline
I Win
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Bend,OR USA
How wide did you open the top and 2nd rings too?
Are these new rings or the old, broken in original to this build rings
Sounds like you may have twisted a oil ring and spacer up when installing the pistons work I've never done that whistling
I would do a leak down test on the motor when cold and hot, rock the crank back and forth a little bit at TDC also scope wrench twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: blow by out breather.. [Re: Cab_Burge] #3048790
06/08/22 06:09 AM
06/08/22 06:09 AM
Joined: Dec 2006
Posts: 4,647
aotearoa
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aotearoa
i was getting a lot of blowby on my 512 from the breather on the rocker cover. I changed it to discharge into a catch can, it now doesn't drip oil from the breather filter so I class that as a win.

Re: blow by out breather.. [Re: rebel] #3048853
06/08/22 11:15 AM
06/08/22 11:15 AM
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Fulton County, PA
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CMcAllister Offline
Mr. Helpful
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Fulton County, PA
Leak it.

Vac-u-pan will help to a point, if you have open headers. Mufflers and/or exhaust system reduces the effectiveness considerably.


If the results don't match the theory, change the theory.
Re: blow by out breather.. [Re: CMcAllister] #3049000
06/08/22 08:49 PM
06/08/22 08:49 PM
Joined: Jul 2011
Posts: 781
wine country
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8urvette Offline OP
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ill do a leak down test this weekend.
the rings were the ones i had used prior to the tear down, so they were " broke in" and sealed to the cylinder. I kept them on the same piston they came off of. They are total seal rings, and i do not recall the gap exactly it was somewhere around .0060 or .0065 per inch of bore, but it really did seem very big to me. I gapped it for a 350 HP kit.

Re: blow by out breather.. [Re: 8urvette] #3049034
06/08/22 11:41 PM
06/08/22 11:41 PM
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Posts: 9,091
Rogue River, OR
Jeremiah Offline
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Rogue River, OR
If it's a 4.3750 bore .026-.028 is what I come up with which isn't horrible. What did you gap them to?

What kind of ring is it? Not sure you can get away with spraying that much without a stainless (Mahle GNS) or ductile iron (Hellfire) top ring.



Re: blow by out breather.. [Re: Jeremiah] #3049113
06/09/22 12:38 PM
06/09/22 12:38 PM
Joined: Jan 2003
Posts: 5,762
Hot Rod Ridge
FastmOp Offline
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Hot Rod Ridge
Could you have installed a set of rings upside down

Re: blow by out breather.. [Re: FastmOp] #3049823
06/12/22 12:25 AM
06/12/22 12:25 AM
Joined: Jul 2011
Posts: 781
wine country
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8urvette Offline OP
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I guess anything is possible.

But I would think if there was an internal issue it would burn oil and smoke out the exhaust. It doesn't. It runs clean. Just blow by out the valley pan.

Re: blow by out breather.. [Re: 8urvette] #3049867
06/12/22 10:34 AM
06/12/22 10:34 AM
Joined: Sep 2003
Posts: 19,237
north of coder
moparx Offline
"Butt Crack Bob"
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north of coder
maybe try a PVC system ?
if so, maybe one of those adjustable versions ?
beer

Re: blow by out breather.. [Re: 8urvette] #3049902
06/12/22 12:27 PM
06/12/22 12:27 PM
Joined: Oct 2010
Posts: 2,393
Ambridge, Pa.
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rickraw Offline
top fuel
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Ambridge, Pa.
You could use a oil separator. I put a upr separator on my ram, works like a champ. No more oil in the intake.

F5C8BDC5-CBEA-489F-924A-B6ABE8FBE3BF.jpeg
Re: blow by out breather.. [Re: rickraw] #3049909
06/12/22 12:37 PM
06/12/22 12:37 PM
Joined: Aug 2003
Posts: 4,662
On the parachute mount
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n20mstr Offline
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On the parachute mount
On my sons small block , we gapped the rings .030 . He welded bungs on his valve covers and ran -10 to the headers . Put a separate -10 to a catch can with a check valve . At idle it pulls just off of 0 on a vac gauge . On the track at the stripe it has 5 inches pan vac


....BAD A$$ STREET CAR.....
Re: blow by out breather.. [Re: 8urvette] #3049912
06/12/22 12:41 PM
06/12/22 12:41 PM
Joined: Dec 2012
Posts: 257
Alberta
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440_Offroader Offline
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Alberta
Might have a top or second ring stuck or not sealing. A small mark on the piston by the ring, or small piece of dirt in the ring land, could hold a ring up. The oil ring can be doing its job, by keeping oil out of the combustion chamber. It doesn't do much for keeping combustion out of the crankcase with its low tension.
It's a lot of work to check, but if it wasn't like that before, then something isn't quite right.
Aside from that, and to be more relative to your question.... Similar to a PCV system with a catch can, I've seen industrial engines have special canister with an element inside. They run in after the air filter (or intake manifold like a PCV), to draw the crankcase pressure down. The coalescing element catches the oil vapor, and the catch can has a small line for oil to drain back down to the oil pan. They have relatively large lines, so tend to draw too much vacuum in some instances. A flow control valve is then installed, to keep crankcase pressure at -1"H2O. Just an idea for you, but may be too much, for under the hood of your car.







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