REFLECTOR: Exhaust/cowling

[Ron Brown]

Tom,

I have the factory exhausts and the factory blister for the #1 cylinder on 
the IO360.

I am not near the plane so I can't go measure how close it is in there - but 
I'd guess it is 1-2" to 3/4" between the bare pipe and the inside of the 
blister.  After 360 hours, the inside of the blister is a bit brown (I 
coated the inside of my cowls with JeffCo (left over from the fuel tanks - 
to minimize the oil bleed through some folks said they were having with 
their cowls).  Another thing that I did was leave plenty of clearance around 
the exhaust outlets where they go through the cowl.  I left about 1" all 
around to promote some air movement there and to the front of the engine.  I 
have a temperature sensor measuring my under cowl temps at cruise and seldom 
see over 180 degrees

The blister and the outside of the blister are fine - still white and stiff.

Perhaps it is because the cowls were heated over a period of time. I.e., 
first engine run procedure, taxi tests then first flight.  The Tg of the 
epoxy can be raised if you don't try to do it all at one time - else you can 
get the sagging.  (applies to engine air plenums too!)

Ronnie Brown

----- Original Message ----- 
From: "Tom" <tomcat05 at comcast.net>
To: <reflector at tvbf.org>
Sent: Monday, December 24, 2007 3:48 PM
Subject: REFLECTOR: Exhaust/cowling


> Had a funky 4 into one exhaust (single crossover), mild steel with no
> slip joints. I knew that this wouldn't work for long and it let go just
> before I needed plane for Christmas travel to be with family (wife is
> pissed). Anyhow I called Velocity and was told the two pipe, 2 into one
> system should be an easy install (IO-360). Bolted up nice and easy but
> the cowling was hitting the pipes at the #1 cyl (left, rear). Cut a slot
> in lower cowl and added a blister with 1/2" clearance, wrapped the
> exhaust and test flew. After landing cowling was bubbling and smoking.
> Tried some insulation on a 2nd test flight but it was touching exhaust
> and had similar issues. 2 questions:
> 1) how much clearance do you need between exhaust pipe and cowl?--I'm
> working on a larger blister now
> 2) what's a good insulation material that's not too wide?? thx Tom
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