Thread: Exhaust blow-by
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Old 04-05-2013, 06:23 PM
BigJohn BigJohn is offline
Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,581

My new S/S springs came today and since my airplane is still torn down for the inspection I dove right in. Removed the muffler and all four pipes. Cleaned all the joints and used the anti-seize paste liberally. Reassembled with nuts just snugged. Moved the muffler around to get it properly centered and torqued down the nuts.

Now for the interesting part. Most of the springs appeared to have very little tension on them, and it didn't take much force to pull the muff outward to loosen the joints. Didn't look right to me. Checked all the springs, and there was not even enough tension on most of them to create a gap between the coils big enough to insert a piece of paper into. VERY CAREFULLY (envisioning ordering new pipes) bent most of the tabs using a big screwdriver as a lever. Adjusted until all springs had enough tension to pass the paper test.

Musing about why my springs were so loose. Did I get a muffler that was welded up wrong? Couldn't be bad springs because new ones were the same as old. At any rate, I think my problem is solved. Time will tell.

I suggest all builders check spring tension when they first assemble their exhaust systems. If you can't pass a slip of paper between the coils investigate further. Call Van's Support before taking any action.
John Peck, CFII, A&P, EAA Tech Counselor, Flight Advisor.
“Master Pilot” Award, UFO Member.
RV-12 N37JP 120176 Flying since 2012.
One Week Wonder Build Team, OSH 2018.
VAF paid through 10/2019.
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