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J-3 with C-90 Exhaust Solution....

Grant

Grant

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At Work.....
We are working on a J-3 with a C-90. We want to avoid cutting the lower cowling to accommodate the drop required to allow the muffler to fit. The muffler hits the Oil temp probe mount. We are doing a starter only, no generator. I cant see a way around cutting the hole but wanted to ask here before I make a cut.
 
Minimize the drop by denting the muffler shroud.

I am finding that cleaning the screen at 50 hour intervals is enough except for a brand new engine, so it can be done at muffler AD time. And lately I have adapted a piece of clear plastic sheet into a chute that makes checking the screen a much cleaner process.

My first installation used stock stacks and an extra gasket on both rear cylinders.

You do know that the C-90-12 requires an STC?
 
Grant said:
We are working on a J-3 with a C-90. We want to avoid cutting the lower cowling to accommodate the drop required to allow the muffler to fit. The muffler hits the Oil temp probe mount. We are doing a starter only, no generator. I cant see a way around cutting the hole but wanted to ask here before I make a cut.
Click to expand...

I had a J-3 mount built 2" longer but it don't have the mounts on it for the j-3 cowl
 
bob turner said:
You do know that the C-90-12 requires an STC?
Click to expand...

Yep, but it does not solve the problem I'm trying to avoid which is cutting a larger hole in a brand new cowling. At the end of the day, I want a very clean and serviceable installation One of the other issues that come up is when we lower the muffler to avoid the screen housing is that it puts the tailpipe shroud close to the gascolator.
 
how about pipe's and muffler's from vetterman?

that's the thing every time you change one thing there's 3 more changes to have to do to make it all work or it seems that way
 
Last edited:
Grant, most of us put the big dent in the shroud. If you take your time and find a fixture to make the dent it won't look bad. You could even fabricate a lipped "U " shape that you rivit in.

Glenn
 
Try the double gasket thing first. Two steel no-blows on back, and either one or a copper gasket on the front. Just dent the muff so it isn't touching the boss. Then try the lower cowl and report back.
 
bob turner said:
Try the double gasket thing first. Two steel no-blows on back, and either one or a copper gasket on the front. Just dent the muff so it isn't touching the boss. Then try the lower cowl and report back.
Click to expand...
I don't know about a C-90 but that is enough to cause a cracked exhaust on an R-680.
 
I will have to look for a picture with the cowl off but this J3 had the muffler dropped down once inside the cowl. Tom might have one.

20170707_160645.jpg
 

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Steve, That's what I was wondering. It would sure be nice to see a pic. I'm having the guys from Aerospace welding come out soon and If I could show them what I want that would be great.

Thanks for all the replies!
 
I do the same thing - pull the cork out and cap the tank every afternoon.

On the drop down muffler - makes checking screen easier and AD a little more difficult. If it wasn't for the additional expense, sounds like an even tradeoff.

On the cracked exhaust stack - my welder was not happy, but I am using stacks almost 7000 hours old, with safe ends (stainless flanges). I haven't seen a set of original stacks that "wore out." I may not be able to continue that way; the welder is now refusing to safe-end these things. The only cracks I have ever had was around the original carbon steel flanges. They were no good to begin with.
 
Hi Grant, I’ve done a couple of J3 exhaust mods for a guy from Sturgis S.D. who puts the 0-200 in.
he has it done just like in Steve’s pics. I use a 2” Exhaust donut which offsets the pipe about 3/4”
sorry I don’t have any pics.
Give me a call if your interested, perhaps I can help. Clint 605-891-1290
 
Bob, there's a really good exhaust shop not far from you, in El Cajon.
Custom Aircraft Parts 619-561-5757 customaircraft.com
They've done a couple exhaust repair jobs for me.
Not a CRS so no yellow tag, but very good work, quick, and at reasonable cost.
 
They have been doing Cub exhaust parts for me since the early 1980s. Made an entirely new muffler from scratch. For the headers - last pair they wanted to scrap and build out of curved tubes. I had to beg - antique look and all that. Clint's welders are the best.
 
Just sold one. Exhaust went with project. Pm me and ill give you buyers info. He puting a c85 on it.
0725181136.jpg
 

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