Blowby, can someone explain...

carbed87

Member
Jun 5, 2005
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tried posting this in talk and just got kids telling me i should have traded my car for a t-top mustang ( i know, wtf)




anyways i need to know about blowby. everything, how it's caused, what can be done to fix it, how do i know if i have it. ways to mabye cover it up.... i think the T/A might have seen it's final night.

thanks guys

(sorry if this is not a technical topic daggs, but im just looking for some answers)
 
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Cylinder pressures push gasses past the rings. The escaped gas is now in the crankcase and is passed through the PCV/breathers.

Simply stated, rings are what allow the gasses to escape in the first place.
 
perhaps but it just sounds not nice to knowingly sell a bagged car to someone and knowingly cover it up. besides if whoever you are selling it to knows anything about cars there are ways to tell if it is buring oil. or driving it a certain way to see if it has blowby. probably the best way to get rid of most of the blue smoke is to have a good set of cats in the exhaust.
 
well thats not even where any of the smoke's coming from. it's just when i take the breather off of the oil feed it puffs out like a train. and it still has ALL it's power, so im stumped you know. and for the record im not covering anything up, i've been in the buyer's position too many times how screwed up it is to sell a clapped out car to someone. whoever gets the car will know whats going on, i can assure you that.
 
I dont know the set-up on those cars. I'd renew the PCV/breathers and make sure there is adequate crankcase ventillation (it sounds like you have a bottleneck right now).

Also, thicker oil can help. If spec is something like 10W-30, I dont see the harm in using that or 10W-40. I assume temps are kinda hot in Denver right now - I wouldnt use a 5W-30 in the heat with an old motor myself.

Good luck.
 
thank you very much, both hissin and 86blue cobra, lol look at this, i actually got more responces on a MUSTANG board then on a thirdgen one, makes you think huh.

thanks again guys.
 
I know how it goes - I've never found a forum that beats SN in terms of quick, knowledgable replies and friendly folks. :nice:
 
An aquentence of mine build big block chevy's. they are usally pretty good power engines. he for some reason ties the breather right into the exhaust. always looks like he is burning oil because he is kinda. i forget why he said he did this but it had to do with excesive pressures in the crank case on brand new high compression engines. perhaps you could get a better pcv and put more breathers on your valve covers. perhaps there is a vacuum leak on the pcv hose so it isn't sucking like it should. perhaps you have a blower cam? maybe you are not making the vacuum you did before effecting the operation of the pcv?
 
Throw some slick 50 in that sucker, but make sure you dont leave the car off for a couple of days at a time, as with the thicker oil and the slick 50 it'll have trouble starting. haha
 
86, more info on how he does that. I wouldnt want the crankcase sucking in exhaust air (a breather being bi-directional).

That's the first I ever heard of that and I'm always up for learning something new. :nice:

Spiff, I'm not too up on additives, but I'd steer clear of anything with teflon in it (if applicable).
 
ok, so i put some 15W40 in it today, with lucas' oil additive. i also installed a home made oil seperator on the hose going to the air filter (made it with a air compressor oil seperator from advance). so i fired it up and it seemed to have a little less smoke until i took it around the block. now the elbow on the passenger side breather keeps popping out and spewing smoke everywhere.

ok, so just so we're on the same page i'll MS paint a diagram of what my pcv system looks like. give me a few minutes.
 
ok, so heres the rendering of how it's setup. the passenger side is just an elbow, and keeps blowing off for whatever reason.


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Hmm, I forgot to read you sig (and note forced induction). It sounds like the rings are just tired and the boost is really exacerbating the issue.

For the crankcase ventillation: Can you clamp the hose onto the breather? I'd want to run the least restrictive breathers I could find.
Did the hose just start popping off after the separator install? If so, try removing the filter element (the catch can will still work - that's how I run mine). That filter can be a big restriction in my experience.

Also, is there a reason for running the breathers into the air filter - rather than having open or vented breathers?


BTW, the caca is great.
 
well i guess your right, with the oil seperator theres really no need for the breather on that one side.

my dilemna right now is making the passenger side hose not pop off, but at the same time keep the smoke at bay. im scared that if i try a breather it'll just smoke a bunch. i'll give it a try tomorrow but i dunno. and yes, it just started popping off, so i'll try taking out the filter element. the idea is just for it to catch the oil it self, not filter the air too lol.

and the tube runs into the top of the air filter which is the part with no paper (you know what i mean right, think cone style)

so would you have any ideas about plumbing that smoke.
 
carbed87 said:
well i guess your right, with the oil seperator theres really no need for the breather on that one side.

my dilemna right now is making the passenger side hose not pop off, but at the same time keep the smoke at bay. im scared that if i try a breather it'll just smoke a bunch. i'll give it a try tomorrow but i dunno. and yes, it just started popping off, so i'll try taking out the filter element. the idea is just for it to catch the oil it self, not filter the air too lol.

and the tube runs into the top of the air filter which is the part with no paper (you know what i mean right, think cone style)

so would you have any ideas about plumbing that smoke.
I'm not sure if I was clear - I meant to remove the little filter element inside the separator. A few of us have had the element get clogged up with oily vapor and it creates a restriction to PCV flow. I just open the top of the separator and take the filter off and put it back together. Gravity still knocks down a lot of oil but with out the restriction (some Terminator guys have done this too).

If feasible, I'd run two closed, vented breathers. The closed breather should keep your engine bay kinda clean and it wont put that nasty crap back into your airbox.
You'd have a small bit of unmetered air (if you have MAF - you might be SD). But the current state of tune might be able to deal with that (forced tunes tend to be a little rich).
 
ok, so i did what you said hissin, i took that little filter out and it seemed to make a difference, but i couldn't really tell because my t-stat housing is now leaking, so i couln't drive it. so once i finish throwing the gasket in for that she should be good to go.