couple of exhaust questions

[Desert Rat]

First and foremost; I love this vetterman exhaust. It fits right out of the box, and was delivered on time and on budget. 5 stars, would recommend to a friend.

That being said, the instructions that come with it are pretty rudimentary, so I've got a couple of questions.

1. How tight should the bolts that hold the slip joints together be? The instructions just say something to the effect of "not too tight". I get that you want a bit of room for the expansion cycle here, but presumably they should be snugged down enough that the bolt doesn't rotate in the hole. Have I got that right?

2. It appears that I've got lots of room where the pipes go under/aft of the firewall lip. How much gap to most people leave here? If I leave about 1" at the red arrow in the picture it will leave about 3/4" between the lower side of the pipe and the end of the cowl shovel. Is this enough, or should I tuck them up a bit higher and have more gap with the cowling?

As always, any other insight is also appreciated

 

[wawrzynskivp]

For exit gap game plan I would (did) split the difference between top and bottom and anything less than 1/2" made me work to get more room. Reflective or reflective/insulating tape here is certainly a good idea.

I see just one strut per pipe. While that may be fine I used two per pipe and did my best to mount them to the engine and not the airframe. One support may allow those pipes to wander owing to the ball joints.

I also flared the ends of those little tubes where they go into the rubber to help with slipping.

As other builders have added in previous posts: do make sure that there is no side loading on those flattened portions of the tubing. Avoid bending those tabs. For me that meant fabricating some wedges so that the flattened portion of those tubes was in pure tension.

 

[Majorpayne317641]

Where can I get these tubes? One of mine cracked and I’m trying to attach a new tube to my oil sump instead of the engine frame.

For exit gap game plan I would (did) split the difference between top and bottom and anything less than 1/2" made me work to get more room. Reflective or reflective/insulating tape here is certainly a good idea.

I see just one strut per pipe. While that may be fine I used two per pipe and did my best to mount them to the engine and not the airframe. One support may allow those pipes to wander owing to the ball joints.

I also flared the ends of those little tubes where they go into the rubber to help with slipping.

As other builders have added in previous posts: do make sure that there is no side loading on those flattened portions of the tubing. Avoid bending those tabs. For me that meant fabricating some wedges so that the flattened portion of those tubes was in pure tension.

 

[D-Dubya]

The notes I have written on my condition inspection form are:

Check exhaust flange mounting nuts (180-200 in-lbs per Vetterman); mid-pipe connections are 8mm nuts (50-70 in-lbs)

 

[wawrzynskivp]

Where can I get these tubes? One of mine cracked and I’m trying to attach a new tube to my oil sump instead of the engine frame.

I always went with Mcmaster carr for odds and ends, but Vetterman may be just as good for this as I am sure they have lots of those.

 

[hgerhardt]

Where can I get these tubes? One of mine cracked and I’m trying to attach a new tube to my oil sump instead of the engine frame.

That tubing is 3/8" steel automotive fuel line material like this: https://www.autozone.com/brakes-and...l-brake-fuel-and-transmission-line/216473_0_0

You can also get stainless, but that's more prone to cracking so I'd avoid it.

Also, when flattening the end for screw attachment, clamp the tube in a vise with a 3/4" piece of round something (socket etc), so that you don't get a sharp crease in the bend which will crack easily in the future.

 

[Desert Rat]

So I think I answered question 1 for myself today.

Turns out that at least in my case, there's a gob of room back there. If you have the pipes 1" below the firewall lip it works out to be about 1 3/8" above the cowling shovel.

Anybody care to comment on question 2? i.e. how tight is too tight for the bolts that go through the connector tabs?

 

[rmarshall234]

Tightness of bolts…
I think you have it right, snug. Tight enough to minimize the relative motion but not so tight as to constrain it.