Blow by

[BuickGN]

I had a motor with severe blowby in the GN for about 10,000 miles. At idle you could see a lot of vapor coming out of the breathers. I can't imagine what it looked like under boost. It was bad enough that the breathers would drip oil onto the headers and smoke. I ended up buying a different style breather that you can attach a 5/8" heater hose to.

Have you ruled out headgaskets? I know some of the guys with the metal shim stacked gaskets had combustion getting past the gaskets. I prefer the Felpro 1000 originally meant for the stage II motors. You will eventually get frustrated enough to tear it down like I did. Spool and power suffer and the oil has to be changed way too often.

 

[Gary Allan]

Originally Posted By: Dyoel182
What does the air filter have to do with the airbox?


Outside of the context of this particular discussion, everything.

I think the reference was to a "foam pad" that's part of the fresh air intake for the PCV system. I could be wrong.

 

[TallPaul]

Yes, the foam pad, or some brands are folded paper elements, but a little filter about 1 by 4 inches that mounts in the air box beside the engine air filter. Anyway, the Aerostar must have a lot of blowby as it pings like crazy under load unless I run premium or retard the timing and heavy blowby would likely lower the octane rating. So I need to try the catch can.

 

[Dyoel182]

Originally Posted By: TallPaul
Anyway, the Aerostar must have a lot of blowby as it pings like crazy under load unless I run premium or retard the timing and heavy blowby would likely lower the octane rating. So I need to try the catch can.


Blowby shouldnt be causing any added pinging. That sounds more like carbon deposits in the engine bay, bad spark plugs or just cheap gas. Regardless make a catch can and see what you filter out.

 

[vacuum_6]

Originally Posted By: BuickGN
I had a motor with severe blowby in the GN for about 10,000 miles. At idle you could see a lot of vapor coming out of the breathers. I can't imagine what it looked like under boost. It was bad enough that the breathers would drip oil onto the headers and smoke. I ended up buying a different style breather that you can attach a 5/8" heater hose to.

Have you ruled out headgaskets? I know some of the guys with the metal shim stacked gaskets had combustion getting past the gaskets. I prefer the Felpro 1000 originally meant for the stage II motors. You will eventually get frustrated enough to tear it down like I did. Spool and power suffer and the oil has to be changed way too often.


Yes I'm using the mult-layer headgasket (cometic). Some people have issues with weeping antifreeze, oh yeah and I'm one of them. With cometics the block must be machined to finish "x" in order to seal correctly. Also a lot of guys use the GM tablets too.

How would I rule out the headgaskets?

 

[vacuum_6]

Originally Posted By: TallPaul
I wonder if my Aerostar 3.0 is doing this. It uses a quart about every 1300 miles, but no blue smoke. Engine has good power, so I doubt the rings are bad. There is no PCV filter on it either. Closed system or something weird like that.

So what do you do, just put a big canister in the PCV hose so the velocity is slowed and [censored] drops out into the can?

Which hose?

Where am I to find space for a can under the hood of an Aerostar?


Dude come on start your own thread.

 

[TallPaul]

Originally Posted By: vacuum_6
Originally Posted By: TallPaul
I wonder if my Aerostar 3.0 is doing this. It uses a quart about every 1300 miles, but no blue smoke. Engine has good power, so I doubt the rings are bad. There is no PCV filter on it either. Closed system or something weird like that.

So what do you do, just put a big canister in the PCV hose so the velocity is slowed and [censored] drops out into the can?

Which hose?

Where am I to find space for a can under the hood of an Aerostar?


Dude come on start your own thread.
Yeah, guess I should have left my post to the question about how to construct the catch can and left out the Aerostar stuff. But still, nobody has show how to construct this catch can. The linked one at Jeggs seems a bit pricy.

 

[Oilgal]

How To Make A Cheap DIY Catch Can and Condenser Barrel.

For the back.

This thing works really well. You just empty the reservoir every so often.

Get one of these HUSKY 1/4 In. Air Compressor Filters at the local Home Despot.

You also will need two 1/4" npt male threads to 3/8" male hose nipple fittings.

I recommend that you buy the optional metal reservoir, to replace the clear plastic one, because oil will break down the plastic one eventually.

I also recommend that you remove that restrictive little white plastic filter that comes with air drill filter. Just screw it out, and then screw in a cheapo PCV valve for Mitsu 3.0, in it's place. Be sure to cut off the PCV tube, where it begins to narrow, and then remove the one way valve and spring inside.

It works much better if you follow those two suggestions.

See the mini catch can, with the optional black metal canister, hanging from my strut brace in the picture below.

If you look closely at my forward PCV hose, you will see I have improvised a small trap, to catch oil vapor without restricting ventilation flow. It seems to work really well. You don't need to empty it if you make sure it is at an inclining angle, so the oil vapor condensed onto the glass, can drain back into the valve cover vent.

Install the filter case, inline on the PCV hose,

without the filter inside.

That old picture of my engine shows it with the filter, and trust me, it doesn't work as well with the filter. Get one at Kragen, Checker, AZAP or AAP. Or use this link to order one from Parts America



Hope that helps you.

PS

I am very early into the rinse phase of an Auto-Rx treatment, and my blowby has greatly decreased. My engine no longer consumes oil anywhere like it did before. Just a suggestion.

 

[Dyoel182]

Thats little "restrictive" while filter isnt really that restrictive in real use. Several of the Honda guys ran tests and showed the car acted exactly the same with it and without it. I'd rather have the extra filtering.

 

[7055]

Originally Posted By: Junior
Originally Posted By: vacuum_6
Originally Posted By: vacuum_6
If an engine is sucking oil thru the PCV (assume the PCV system is operating fine) due to blow-by. Is it better to retain the stock system and use a catch can or move the PCV system to the valve cover or it does not matter?

If the PCV system is no longer sucking oil then does the engine begin to burn it instead?


I'm trying to understand what happens to the blow-by oil if a catch-can is not used. Does it get burned? Is it better to catch it and then pour it back inon the engine? I understand that all engines have some blow-up but I'm talking about excessive blow-by.


A PCV system forces an engine to "eat" all of its blow by. It is a means of pollution control. In the old days before emissions and polution control, the blow by was just vented to atmosphere outside the engine.


Thats not the only reason, there needs to be vacuum in the crankcase, thats why the PCV is hooked up to a source of vacuum (your intake). It needs vacuum to vent of the blowby and help pull the oil off the walls and keep it in the oil pan where its needed. This is even more so important on cars with forced induction. The PCV is a ventilation system, it needs to be hooked up to vacuum to ventilate the crankcase.

 

[Junior]

Originally Posted By: 7055


Thats not the only reason, there needs to be vacuum in the crankcase, thats why the PCV is hooked up to a source of vacuum (your intake). It needs vacuum to vent of the blowby and help pull the oil off the walls and keep it in the oil pan where its needed. This is even more so important on cars with forced induction. The PCV is a ventilation system, it needs to be hooked up to vacuum to ventilate the crankcase.


What? A vacuum in the crankcase is not necessary as long as it is vented. Think pre 1964.

It does help the seals live a happier life and modern cars are designed to operate this will and will probably not run correctly without but a PCV system was only develped for emissions

 

[Oilgal]

Originally Posted By: Dyoel182
Thats little "restrictive" while filter isnt really that restrictive in real use. Several of the Honda guys ran tests and showed the car acted exactly the same with it and without it. I'd rather have the extra filtering.


Any reversing incoming air would still be filtered, unless you install the catch can wrong, and so there is no reason to leave that filter on.

As for what "the Honda guys say". I wouldn't rely on such reports. I tested it myself, and I discovered it was too restrictive. It may, or may not, be OK for small Honda engine, but there is no need for it anyway.

 

[Dyoel182]

Why would filtering air coming both ways be a bad thing? I'd rather have the filter there to force the oil to separate than rely on gravity to pull it out of the air for me.

 

[vacuum_6]

Originally Posted By: Oilgal
Get one of these HUSKY 1/4 In. Air Compressor Filters at the local Home Despot.

You also will need two 1/4" npt male threads to 3/8" male hose nipple fittings.

I recommend that you buy the optional metal reservoir, to replace the clear plastic one, because oil will break down the plastic one eventually.

I also recommend that you remove that restrictive little white plastic filter that comes with air drill filter. Just screw it out, and then screw in a cheapo PCV valve for Mitsu 3.0, in it's place. Be sure to cut off the PCV tube, where it begins to narrow, and then remove the one way valve and spring inside.

It works much better if you follow those two suggestions.


I don’t see how the filter is restrictive. What’s the CFM rating on it? Most cars pull 15" of vacuum? Which 15” = ~7.5 psi.

 

[Oilgal]

Originally Posted By: Dyoel182
Why would filtering air coming both ways be a bad thing? I'd rather have the filter there to force the oil to separate than rely on gravity to pull it out of the air for me.


You're right, it wouldn't be a bad thing. I think your understanding, of how a properly configured catch can works, is just incomplete is all. There is more than gravity involved.

If you have a central tube (the modded PCV valve I recommended), connected to where that little filter screws in, which extends three fourths of the way down into the reservoir, 'and' you make certain that the CC ventilation gases flow from the engine to the catch can 'and' down through that same central tube ..... so the gasses must then turn and flow back up to the top of the catch can .... to then exit through the other port at the top of the catch can , the oil vapor, (in addition to some percentage at least of whatever micro particulate exists) will be separated by inertia, surface adhesion and gravity, .... and probably some other "stuff" I haven't thought of too.

So anyway there is more than just gravity involved. You must make certain, that you install the catch can in the way outlined above, or it wont work worth a (rhymes with) bam.

The method you speak of, means that at most you will be relying on that tiny plastic filter alone, which will also break down from heat 'and' exposer to the corrosive CC gases being ventilated.

If it helps, I didn't think of all this stuff.

I was schooled on this by a friend of mine, who is a whiz bang engine builder and custom fabricator, who has had his work featured in just about every (rhymes with) bam Hot Rod and Car Magazine you can think of, including Hot Rod Magazine. I am just a dumb old lady OK?

 

[Oilgal]

Originally Posted By: vacuum_6


I don’t see how the filter is restrictive. What’s the CFM rating on it? Most cars pull 15" of vacuum? Which 15” = ~7.5 psi.


OK. Then you should just go ahead and leave it in. You have my full support on that.

 

[vacuum_6]

http://www.homedepot.com/webapp/wcs/stor...ocStoreNum=8125
21 SCFM flow capacity @ 90 PSI.





http://www.mcmaster.com/nav/enter.asp?pagenum=924
22 CFM max @ 100 PSI


http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_763433_-1_10449

Jegs side there is not CFM rating on this item.

 

[vacuum_6]

Originally Posted By: Oilgal

OK. Then you should just go ahead and leave it in. You have my full support on that.

So if you leave it in...what, less vacuum will be pulled thru. Don’t see why that is bad, unless the car needs to see a specific flow thru that device. Please explain to me why that is bad. Thanks.

 

[Oilgal]

Here is a picture of the the inside of a catch can.

Note: If you use steel wool, make sure, it is the heavy stuff that wont shed microscopic particles. My expert friend, I told you about, said I should not use anything because it was unnecessary anyway.

The picture also shows an incoming CC ventilate (engine side) tube that is too long.


SPECIAL note:

If that doesn't answer your question vacuum_6, then you should leave all, car repair and especially engine modding, to a professional.

Just funnin with ya.

 

[BarkerMan]

The PCV system is more sensitive to the new Xw-20 oils. They produce more vapors in the crankcase. In racing where you have qualifying oil (thin) and race oil (thicker) the crankcase vacuum pump or other devices must be changed to account for the different viscosities. I don’t know if this has anything to do with street engines but it may be of interest when developing a catch can. Instead of trying to figure out baffles inside a container you can experiment with two cans in series and observe the results. You can then fine tune your system to get just the right amount of pressure drop to separate the solids and liquids from the gasses. You can then experiment with height and distance from heat sources and insulation. We use catch cans in series but have the advantage of cutting and welding the catch cans which might be more difficult in the home garage. We have found that diffusing the flow is more important than baffles, that is changing the volume of the space the vapors travel through. Another solution is to use glass or plastic and glue the baffles in. You want to consider blocking the line of sight from the top of the can to the bottom with overlapping baffles. Restricting the volume in the path drops the pressure and expanding the volume raises the pressure. We have also used a solenoid valve that is controlled by a vacuum signal and can be tuned while the engine is running. Experimenting has proven more useful than common sense but I think that even in street engine these devices are worth the trouble just because the stuff that comes out looks nasty.