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Old 12-29-2021, 05:22 PM
ERJDriver ERJDriver is offline
Join Date: Sep 2020
Posts: 77
Default Io360 A1A loose intake flanges

Hey all, I noticed one or two cylinders the pipes are loose in the flanges. It’s like the clearance is too deep between the flange, the pipe, and the mating surface of the cylinder. Is there a way to fix this or do I have to buy new pipes/flanges
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Old 12-29-2021, 06:57 PM
scsmith scsmith is offline
Join Date: Jan 2008
Location: Ashland, OR
Posts: 3,060

One option might be the great o-ring seal system that SDS sells. It was jointly developed by Ross Farnham (SDS) and Mike Robinson (Toobuilder).

You do have to cut the tubes to install the new clamping flanges, then re-weld the tubes. Vince at Vetterman Exhaust did that for me for a modest fee. Alignment was perfect.

I highly recommend it. It is a forever fix to a potential problem that is sometimes hard to diagnose.
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 700
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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Old 12-30-2021, 06:55 AM
pa38112 pa38112 is offline
Join Date: Mar 2008
Location: Clarksboro, NJ
Posts: 1,032

Why do you have to cut the flanges? On my O-360-A1A I just removed the intake pipes and slipped the old ring off of the free end and slipped the new one on. Is the IO intake a manifold?
2004 RV6A Flying
2002 RV6A Flying
1978 PA38-112
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Old 12-30-2021, 08:06 AM
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rv6ejguy rv6ejguy is offline
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 6,190

Engines using a formed flange and O-ring seal at the sump end as below will require that the tubes be cut and re-welded. On engines which use a hose and clamp connection at the sump end with 1.5 or 1.75 OD induction tubes, no cutting is required.

Some aftermarket tubes have the tubes enlarged to 2" OD at the sump connection. These will also require tube cutting and re-welding.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 456.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016

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Old 12-30-2021, 12:10 PM
ERJDriver ERJDriver is offline
Join Date: Sep 2020
Posts: 77

What's something like that run?
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Old 12-30-2021, 12:11 PM
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Dan 57 Dan 57 is offline
Join Date: Sep 2018
Location: LSZF
Posts: 963

Same as pa38112 here. Nothing but just replacing the flanges on my O-360-A1A (converted to hollow crank).
An expensive but worth every penny SDS mod on anyone’s engine. And Ross is a pleasure to deal with

I do also recommend their rocker covers, leak free heads for sure
- ain't the Destination, but the Journey -

RV-6.9 #25685, slider, O-360-A3A (carb/dual Lightspeed II), MTV-12-B, HB-YLL owner & lover
RV-4 #2062 HB-YVZ airframe builder
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Old 12-30-2021, 01:29 PM is offline
Join Date: Jan 2017
Location: Battle Ground WA
Posts: 465
Default Second solution

OK Maybe I think to much, But, I have the same tubes as Ross shows on my I0-360. If I wanted to put the SDS O-Ring system on my RV-6 ( I have them on my RV-6A) I would probably just cut the tubes and put sleeves of hose and some of Ross's CT clamps on them. Why not? I realize there is only an O-Ring holding into the sump. But it should work.
My three cents worth and not a penny more Art
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Old 12-31-2021, 04:09 AM
ERJDriver ERJDriver is offline
Join Date: Sep 2020
Posts: 77

Interesting idea !
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Old 12-31-2021, 05:36 AM
theduff theduff is offline
Join Date: Jan 2012
Location: L-18
Posts: 372
Default Loose intake flanges on 200 hp sump

Doing an inspection on my intake tubes I noticed one had fuel staining around the flange. I removed the offending tube and while supporting the tube carefully slid the flange across ia flat plate with 300 grit wet/dry sandpaper a couple of times which left a beautiful witness mark on the assembly. Sure enough on one side the flange was making contact before the edge of the tube itself. I filed and sanded the flange down until the intake tube made full contact all the way around. Reinstalled the tube and flange and no more leak.
It appears to me that tightening the intake bolts to the head over time pull the edges of the flange down and bow the collars. Simple fix with about an hour of work.
RV-4S (slider) Builder and 1300 hr RV Pilot
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Old 12-31-2021, 09:17 AM
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Toobuilder Toobuilder is offline
Join Date: Jul 2009
Location: Mojave
Posts: 4,902

Unlike the parallel valve intake hold down flanges which slide off the tube and can be reworked easily, the angle valve units are married to the tubes for life. Once they start to rattle around in the flange clamps, they keep digging deeper and deeper. The "fix" is to surface the mating flange until the recess is shallow enough to make the intake tube a bit proud. The easiest way to do this is to cut the tube and have the flange surfaced or replaced, but at that point you might as well do the SDS o ring mod and be done with it. Yes, you can slide the flange down the tube and go at it with a file, hoping to keep the surface true, but frankly I can cut and reweld a tube in less time than that would take.
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
Harmon Rocket II -SDS EFI
1940 Taylorcraft BL-65
1984 L39C - SOLD
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