Shoptalkforums.com

Has anyone ever had issues with blow by causing oil to leak from the rear main seal?

If the venting system for the engine is plugged or not working well things like that can happen. The pressure has to escape somewhere so it will find the easiest outlet.

On a stock "open vent" systems the outlet tube can get blocked just by age; the collection of vented oil filled gasses collect in the tubes usually around a bend or something like that and eventually closing the system. A clogged breather cap (or two) can have the same effect as well as over pressurizing an engine especially if, say, you have weak rings or are shifting at 1-trillion RPMs and the venting system isn't up to that.

Very common in the open vent engines from years ago. I've had it happen in the old in-line Chev and flathead V8 Ford engines too.

Lee

Thanks, I have Both valve covers vented, and the oil fill vented. I was hoping that was enough but it must not be

It may be enough and you have ring issues? Any more details in your setup?

One time I noticed I had some blowby. Out of curiosity I took the cap off while running and had this:
I was getting 130psi cranking compression on all cylinders and upon teardown I had at least double the ring gap that was acceptable. Some 3 times the gap. It ran fine and didn't push oil out anywhere but I felt it was a lot of air coming out of rhe fill tube.
https://youtu.be/tktLuA7GkzM

There are a lot of reasons for blow by such as the piston rings have too much gap in the ring seats or the ring gaps in alignment just to name a couple.

A basic for those who don't know: http://www.enginebasics.com/Engine%20Ba ... Rings.html

Thisi s a good basic understaning video; https://www.youtube.com/watch?v=Wadmzv1Vs0Q

Your problem may not be covered there but something to look into.

If it were just one cylinder that was the problem you would get/feel a "puff" of air from that cylinder with the breather cap off (seen that several times in my life). If a ring was installed upside down then other things could show it. https://forums.vwvortex.com/showthread. ... upsidedown This also alludes to the piston vs. cylinder distance not being pfitted properly.

Remember that the rings have to seat themselves and that is usually say in the 20 to 100 miles range.

Just so many things. Again, re-check the compression.

Just habe to be sure you understand that checking compression may not tell the story. Like I said mine was showing 130psi on all cylinders but I was up to 3 times the limit on ring gap on some of mine. I even checked it with 2 different gauges.

It truly pains me to admit this, when I built this engine I used wise pistons and rings, when I gapped them to their recommendation. however the number i used wasn't recommended ring gap, it was a conversion factor. so instead of doing math with their number I used it. I have .050 and .055 ring gap. what a GOON. new set is in the mail. learn from my mistakes. Slow down

Your not a "Goon" unless you don't learn from your mistakes
.
Like I said before: you can be young and make mistakes, survive them and learn from them before you can be old and wise.

Lee

I got this in an e-mail reciently: "Remember: Don't make old people mad. We don't like being old in the first place, so it doesn't take much to annoy us."

Two wrongs don't make a right but three lefts do.

ha ha thanks Everyone here is always good with advice. . well I'm sitting her trying to decide, I cannot for the life of me remember if i did the math or not. Im struggling with memory, im 90% sure I didn't. its the only thing that will explain the massive amounts of crank case pressure I have at idle. i have pressure coming out of the breather cap almost identical to the video above. Thanks All

Bummer. Only real way to know is to pull a head and cylinder and check it. Or could always do a leakdown test and see what you come up with.

I did a leak down test and I’m getting 8-10% leak down. I think that’s pretty decent. What do you think about the fact that it is vented so much. That it’s suckibg air via the valve covers

That's not bad for leak down. It's sucking air in from the valve covers?

we like pic's You may have to small dia. breather hoses?

i'm planning of using 2 AN10's but still not sure it will be enough on my 2110
currently use one to atmosphere and it blows out oil vapour when running hard