What is BLOW BY?
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TECH Apprentice
Joined: May 2002
Posts: 383
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From: Jacksonville
What is BLOW BY? Lately, i've gotten hit with a problem with excessive oil in my Supercharger Ducting. I thought it might be the seals but it doesn't appear to be since the oil seems to come from the intake side. Upoun further investigation I traced the problem to the hose that fits into a gromet on the blower intake elbow. This hose attaches to the passenger side valve cover. I really have no idea what the function of that hose is. It doesn't appear to do with the PCV does it?
Anyhow, I pulled my headunit off the car to inspect the oil drain hose. I had a theroy that maybe there was some issue with the oil draining out of the headunit but when I blew into the oil drain hose I could feel/hear it coming out of this Passenger Valve Cover Hose. I thought that was odd.
I'm thinking about rigging up some sort of Oil Catch can but I thought for the time being I'd just cap off that Passenger side valve cover unless anyone feels that would be a very bad idea?
Thanks for reading and I would truly appreciate your thoughts and opinions.
Anyhow, I pulled my headunit off the car to inspect the oil drain hose. I had a theroy that maybe there was some issue with the oil draining out of the headunit but when I blew into the oil drain hose I could feel/hear it coming out of this Passenger Valve Cover Hose. I thought that was odd.
I'm thinking about rigging up some sort of Oil Catch can but I thought for the time being I'd just cap off that Passenger side valve cover unless anyone feels that would be a very bad idea?
Thanks for reading and I would truly appreciate your thoughts and opinions.
TECH Senior Member
Joined: Nov 2001
Posts: 11,603
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From: Chi-Town, IL
Re: What is BLOW BY? On my 346 I am currently running 2 breather valves on the valvecovers, I haven't had a case where the dipstick would blow out, but my oil filter leaks and oil drain plugs leaks because of the pressure, not sure as to why...
Re: What is BLOW BY? BIGBOS
Sounds like you have some broken piston ring lands. I know this from experience. When I first put the smaller pulley on I ran lean and detonated. I didn't relize it at the time. I was blowing oil out of the dipstick tube under high boost. (11-13)psi. I tried every thing. I installed pcv filters. I even tried a vacuum pump on the crank case. Nothing really helped. I ended up tearing down the engine. I found I had 2 pistons with broken ring lands. I didn't have any noise in the engine. There should not be that much pressure in the crank case to cause this. When that much pressure you have a problem. A catch can is just a band aid.
Sounds like you have some broken piston ring lands. I know this from experience. When I first put the smaller pulley on I ran lean and detonated. I didn't relize it at the time. I was blowing oil out of the dipstick tube under high boost. (11-13)psi. I tried every thing. I installed pcv filters. I even tried a vacuum pump on the crank case. Nothing really helped. I ended up tearing down the engine. I found I had 2 pistons with broken ring lands. I didn't have any noise in the engine. There should not be that much pressure in the crank case to cause this. When that much pressure you have a problem. A catch can is just a band aid.
TECH Fanatic
Joined: Nov 2001
Posts: 1,055
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From: Chi-Town
Re: What is BLOW BY? BOS they are essentially the same thing....except the catch can is obviously catching the oil whereas the filters might leak a little once in a while.
Up to you do decide *shrug*
i'm just using 1 filter on each valvecover and hopefully that works out ok for me
Up to you do decide *shrug*
i'm just using 1 filter on each valvecover and hopefully that works out ok for me
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Re: What is BLOW BY? As I mentioned the last time I saw you Brian at the MFBA dyno day at Speed Inc., I cannot underscore how dangerous I think breather setups are like that.
I had a similar setup a while back, and I will tell you that the breathers didn't seat well into those grommets, and furthermore, they would seep and blow out way too much oil onto my headers. Our valve covers are really low, and when we jump on and the throttle a lot of oil will roll back into the rear breather and spew out... The ideal solution would be to have tall Mopar style breathers but there is a clearance problem. Oil fires are nothing to ignore.
I URGE you to buy some pcv's and then then to run rubber hose to a remote catchcan and then back in to the blower ducting.
Also, to answer the comment about crankcase pressure, my 422ci had a lot of crankcase pressure, all the built ones do. None of my ring were messed up. So you will see some smoke out of the breather.
I had a similar setup a while back, and I will tell you that the breathers didn't seat well into those grommets, and furthermore, they would seep and blow out way too much oil onto my headers. Our valve covers are really low, and when we jump on and the throttle a lot of oil will roll back into the rear breather and spew out... The ideal solution would be to have tall Mopar style breathers but there is a clearance problem. Oil fires are nothing to ignore.
I URGE you to buy some pcv's and then then to run rubber hose to a remote catchcan and then back in to the blower ducting.
Also, to answer the comment about crankcase pressure, my 422ci had a lot of crankcase pressure, all the built ones do. None of my ring were messed up. So you will see some smoke out of the breather.
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