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  #1  
Old 06-12-2022, 10:00 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 3,203
Default breather pipe suggestions?

I have an aluminum 5/8" diameter breather pipe running down my firewall, perfectly bent to terminate just above the exhaust pipe, just how I like it.

The engine breather fitting is a 3/4" tube fitting on the accessory case.

I have a 3/4" i.d. to 5/8" i.d molded rubber elbow on that fitting, then a short section of aluminum tube, then a 5/8" molded rubber elbow that connects to the aluminum tube running down my firewall. All is great, except.....

The two molded rubber elbows are heater hose, not PCV/emissions hose. They are not very resistant to oil. So after a few years, they are kind of swollen and sweat oil on the outside a little bit. So I have just been changing them every couple of years.

But wouldn't it be nice if I could find molded rubber elbows in PCV hose (not to be confused with PVC ) that was the right size?

Ideas?

I'm more than a little reluctant to change the tube fitting on the engine, it is a very lightweight fitting, and it was installed into the accessory case when the engine was first built, probably before humans walked on the moon. My hunch is that if I put a socket on that fitting and try to unscrew it, it will rumble and buckle into a mess.


Does anyone know the I.D. of the molded hose that Van's sells for breathers? If it is 5/8", that would at least solve half my problem.
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WW 200RV
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also
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Last edited by scsmith : 06-12-2022 at 10:03 PM.
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  #2  
Old 06-12-2022, 10:50 PM
OKAV8r OKAV8r is offline
 
Join Date: Feb 2007
Location: Seattle
Posts: 270
Default

stick with 3/4 until the line reaches an apex as high as possible (without hitting the upper cowl, of course), then neck down to 5/8. This allows oil mist to drop out of the flow during low velocity, and gravity feed back toward the engine.
I made a reducer using a piece of 3/4 copper, a 3/4 to 5/8 sweat reducer, and a stub of 5/8 copper, then coupled up with short chunks of MIL 6000D hose
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  #3  
Old 06-12-2022, 10:57 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
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Default

Quote:
Originally Posted by OKAV8r View Post
stick with 3/4 until the line reaches an apex as high as possible (without hitting the upper cowl, of course), then neck down to 5/8. This allows oil mist to drop out of the flow during low velocity, and gravity feed back toward the engine.
I made a reducer using a piece of 3/4 copper, a 3/4 to 5/8 sweat reducer, and a stub of 5/8 copper, then coupled up with short chunks of MIL 6000D hose
That doesn't really help solve the issue of the 90-degree elbows
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Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 700
also
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Dec 2021
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  #4  
Old 06-12-2022, 11:11 PM
OKAV8r OKAV8r is offline
 
Join Date: Feb 2007
Location: Seattle
Posts: 270
Default

Quote:
Originally Posted by scsmith View Post
That doesn't really help solve the issue of the 90-degree elbows
Sweat on a copper 90?
Just offering up what I have done, I'm sure you can engineer the system more elegant than what I cobbled together
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  #5  
Old 06-12-2022, 11:11 PM
Bavafa Bavafa is offline
 
Join Date: Oct 2007
Location: Sacramento, CA
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The way I did this, was to use a 3/4 ID hose to go to a 3/4 OD aluminum tube. The 3/4" hose was long enough to make a 180 to the firewall and then a 90 down to the aluminum tube. This made of a nicer and perhaps less restrictive turns.
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  #6  
Old 06-13-2022, 04:29 AM
Larry DeCamp Larry DeCamp is offline
 
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 1,259
Default What about this Steve ?

Make an elbow form out of foam sealed with West 105. Wrap it with Dan’s Ultra Black impregnated glass tape as thick as you like. Pour in the Acetone and install ��
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Last edited by Larry DeCamp : 06-13-2022 at 04:32 AM.
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  #7  
Old 06-13-2022, 06:13 AM
TS Flightlines TS Flightlines is offline
 
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 3,113
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Try premolded silicone 90* hose. Or, we did this for a client. Convoluted teflon, impervious to oil, and has pretty good flexibility. He wanted just enough to connect to his aluminum tube. 3/4 ID, so he had to expand the aluminum tube on the hose end to fit tight, then clamp. Think he wrapped it with firesleeve tape, ot maybe took a piece of 3/4 OD, .049 wall aluminum tube and forced it over the breather tube to "enlarge" the end to fit the hose.

Bullet proof, and oil doesnt affect it.

Tom
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  #8  
Old 06-13-2022, 06:41 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 7,476
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I had a similar challenge on the 10. I used silicone hose to get to the down tube, but couldn't find the elbows I needed (can't get much bending in that type of hose) I used a bit of 3/4" copper tube and elbows, soldered up to match the angles I needed. In your case, 1/2" copper tube should have an OD around 5/8", so just solder a small stub of tubing on each end of the elbow for the transition to rubber or silicone. A street elbow will only require one stub. It adds a couple ounces of weight, but avoids a hassle. Type M is lighter than L or K.

You can also find pre molded elbows in silicone at the race shops, like summit. Not sure you will find 5/8 ID though.

Larry
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Last edited by lr172 : 06-13-2022 at 06:53 AM.
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  #9  
Old 06-13-2022, 07:27 AM
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wjb wjb is offline
 
Join Date: Nov 2012
Location: Half Moon Bay, CA
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Default

Try going to your local Napa or equivalent auto parts store and ask if you can look through their stock of pre-molded tubes ... you might be able to find one with a 90 deg turn and the correct (different) ID's somewhere along it's length .. just cut to fit.

I had a friend in college with a Saab 900, which he was fiercely proud of. While on a road trip to a wedding, one of the rubber cooling tubes sprung a leak, a small elbow with different IDs on each end. We were stuck in Deming NM; the guy at the Napa shop chuckled when we asked if they had a spare and said that the nearest Saab dealership was in Phoenix. I tried the tube search trick, and found a perfect replacement in the middle of a tube for some type of Chevrolet.

From that day forward, the Saab was always referred to as "The Chevy".
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  #10  
Old 06-13-2022, 07:38 AM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
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I used MIL6000D hose to run from the breather, up over one of the motor mount truss work and then down the firewall -- about the same location as the stock aluminum tube with adel clamps at strategic places along the firewall. At the exit point, I installed a piece of aluminum tube (3/4" IIRC) and positioned it about 1/2" or so from the exhaust pipe. It's the same diameter as the breather nipple from end to end -- possibly better flow characteristics.
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Last edited by bjdecker : 06-13-2022 at 07:41 AM.
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