Heavy Breather!

[Valkman]

I'm having trouble with crank case breathing. I have a 340 with a wild solid cam and Ansin (same as Mopar Performance) cast aluminum valve covers with 2 twist on filler holes. I've tried several different ways of vent, from an open breather cap along with or without an added PCV to the carb as but oil still spills out the breather. I also tried a breather vent to the air cleaner but it spills oil all over the air filter. Is something I'm missing, or is there issue I'm not aware of?

 

[cannucky]

first obvious question would be do those covers have the shields under the breather holes?

 

[Valkman]

first obvious question would be do those covers have the shields under the breather holes?

One does, one doesn't ( I use that side to fill)

 

[GTXperience]

first obvious question would be do those covers have the shields under the breather holes?

Yes, was going to also ask if they were baffled. Just to clarify, which one is spitting up (or is it both)? Any pics to share?

 

[rumblefish360]

Oooo, baffles under the breathers are a must. Install the baffles, report back.

 

[Valkman]

I tried just using a PCV valve (this side in baffled ) and a non venting cap on the other side. When I launched hard it sprayed oil everywhere, and from what I could figure it blew past the seal around the PCV.

 

[340doc]

PVC on one side and a vented breather on the opposite side to draw air in. Is there a way to install a baffle on the other V cover?

 

[yellow rose]

I tried just using a PCV valve (this side in baffled ) and a non venting cap on the other side. When I launched hard it sprayed oil everywhere, and from what I could figure it blew past the seal around the PCV.

This is starting to sound like a ring seal issue to me. You should be able to run just 2 breathers and not have it blowing oil everywhere.

 

[69_340_GTS]

You need baffles under the breathers, and/or under the PCV. There is no way around this.

 

[Valkman]

This is starting to sound like a ring seal issue to me. You should be able to run just 2 breathers and not have it blowing oil everywhere.

I hope not! The engines not that old and it has good oil pressure, and it doesn't smoke.
I'll put the baffle back in on the other side and see if that helps.

 

[340doc]

Be sure to run a vented breather opposite the PCV. Hope the baffle helps!

 

[Alaskan_TA]

Try a compression test also.

Oil blow by out the breather is a common sign of bad rings & / or a scored cylinder wall.

 

[Valkman]

Try a compression test also.

Oil blow by out the breather is a common sign of bad rings & / or a scored cylinder wall.

I did one a little while back and all was good, I'll have some time this weekend to take a look at it.

Thanks all for your help

 

[nm9stheham]

The PCV is not going to do anything much at all to pull vapor pressure out of the crankcase at wide open throttle.

What type of piston rings do you have? And pistons?

What rocker arm system do you have?

 

[Cudafever]

baffles are a must and the first step. vapor is what is trying to come out but if there is oil in its path, it will take it out with it. Baffles and then worry about more expensive solutions. My MP Valve covers didn't come with baffles and i had to make some for it.

 

[MopaR&D]

Add a baffle to the valve cover that doesn't have one, keep the PCV on the one side then replace the filler cap with a breather and the hose going to the air cleaner. Your engine can have good cranking compression (checking with a gauge) while still having some blowby if the rings were gapped wide and/or you are running a higher compression ratio. I don't think it should be blowing oil like that though, try the breather on the other side and see what happens next time you floor it.

 

[Valkman]

The PCV is not going to do anything much at all to pull vapor pressure out of the crankcase at wide open throttle.

What type of piston rings do you have? And pistons

Don't know bought the engine as is, so I don't know a whole lot about it.

What rocker arm system do you have?

Crane 1.5 aluminum Roller rockers

 

[yellow rose]

Don't know bought the engine as is, so I don't know a whole lot about it.



Crane 1.5 aluminum Roller rockers

I bought a used engine once. Fired it up and sounded good, but it had issues. It idled as rough as anything I ever had on the street, yet it would fall on its face after 4800 RPM.

The other issue was blowby. You couldn't stop it. I would pull to a stop light, and if I had to sit there very long, the pig would leak oil. So I would fix the leak. Then it would move to another spot and keep leaking.

I finally gave up, and pulled the engine to figure out what the cam was and look at the leaking pig. BTW, I did a compression test and it was fine.

What I found was a reground cam that was JUNK, and some dilhole had used a ridge reamer on the top of the bore and blew it almost .020 big. And th cylinders had .008 taper and I forget the out of round. All the top rings were broken, I assume from all the taper, especially at the top. Had to take it .040 to clean it up. Also installed a .509 cam that had a better idle and pulled to 6200.


Lesson learned.

 

[Valkman]

Yellow rose I agree with you but got a sweet with this motor, I bought the whole car pulled the drivetrain out and sold the car for a net profit. I didn't expect much from a motor that I know little about and I'm putting together a motor of my own but that's going take time and money I don’t have right now. In the mean time I'm dealing with what I have. This 340 runs pretty good, but the cam is way too wild for my taste, and if I can get it sorted out I'll put a streetable cam in it run it till I can get the motor I want.

 

[MopaR&D]

You get a chance to try swapping out the filler cap for a breather?

 

[AJ/FormS]

I think a leakdown test would be on the top of my list.
Make that second.Or maybe third.
1)I would first verify that the crankcase oil-level is not overfull. When the crank gets to beating up on the oil, all that aerated oil has a hard time getting back into the pan in a timely manner.
2)Then, cuz I have the tool, I would do a blow-by test.
Then, if the oil level is correct,(dont trust the stick calibration on an unknown engine), and the blow-by tester indicates and confirms a problem;
3)then I'd go looking for a scored cylinder wall. I use the same LD setup. I just crank the pressure way down,and back the piston part way down the cylinder, stopping in several places, to check for air sneaking around the rings; especially when it gets to where the wrist-pin lives.Oh-Oh......
And of course, before I would do any testing, I would install those pesky baffles as already mentioned, and some large breathers with oil-separation capabilities, you know, the ones with the mesh inside.

On another note. If you are gonna put a smaller cam in that engine, you have to be careful that your Dcr and cranking cylinder pressure do not exceed the octane limits of your locally available gasoline. So a compression test will serve two purposes; 1) to see what we will see, and 2) if there is room for a smaller cam.

 

[nm9stheham]

Crane 1.5 aluminum Roller rockers

Just one further suggestion to consider and why I asked about the rockers: If someone used AL rockers and did not set the right side clearances, and then add something like grooved cam bearings or a grooved cam journals to have continuous oil flow to the rockers, the rockers may just be plain over-oiling the head area and putting so much oil up under the covers to as to cause the problem.

 

[AJ/FormS]

Good thinking!

 

[nm9stheham]

And FWIW, if over oiling in the heads is the problem, then you can find out really easy. Remove a valve cover, and start it up. You'll know real fast when oil starts spraying out over from between the rockers! It ought to just ooze out and might even take some time to start oozing at idle. Take a video....we wanna the see the mess LOL

 

[AJ/FormS]

Well,since he has at least one VC without a baffle, he could probably see it right thru that filler-window.