Can pipe thread black-iron be too tight in an aluminum block?

[ebinmaine 69,230]

This might sound like a bit of an odd question but... what brings it up is that when I started the Briggs engine that I'm installing on my honey's 657, the exhaust started to fall when the engine got hot.

This would be because the aluminum expanded at a far greater rate than the steel that the pipe is made out of and simply became loose.

I do understand that.

What I am wondering is - is there such a thing as turning that npt threaded muffler pipe in... Too far??

 

I am going to make up some kind of a flat steel bracket to support the pipe at a 90 degree angle.

I just want to make sure that it is as tight as it should be.

[KC9KAS 4,741]

I have seen many a muffler pipes being held tight with a conduit nut.

[wallfish 17,140]

Too tight and it can certainly crack that aluminum block.

Get your self a "nut" and cinch the pipe. Also couldn't hurt to support it as well

 

[ebinmaine 69,230]

Just now, KC9KAS said:

I have seen many a muffler pipes being held tight with a conduit nut.

 

I thought that would work too so I did put one on.

 

Thing is, the direction of loosening is also the direction that is in favor of gravity.

So when the motor got hot, the muffler just started to fall.

[KC9KAS 4,741]

2 minutes ago, ebinmaine said:

 

I thought that would work too so I did put one on.

 

Thing is, the direction of loosening is also the direction that is in favor of gravity.

So when the motor got hot, the muffler just started to fall.

Then a bracket is probably your best bet!

We have to be fabricators sometimes to keep these horses alive and kicking!

[wallfish 17,140]

Check out some pics of the older horses with Techy engines. Like a 654. Those aluminum block engines used an exhaust support from the factory.

[ebinmaine 69,230]

5 minutes ago, wallfish said:

Check out some pics of the older horses with Techy engines. Like a 654. Those aluminum block engines used an exhaust support from the factory.

Ahhh...

So my idea might even work!!!

[Machineguy 877]

If you have room on the block at the exhaust port. You may be able to drill and tap a small grub screw hole to jam lock the conduit nut after it’s tightened. An 8-32 set screw with high temp copper anti-seize on it would allow it to be removed later. That would stop the rotation after it’s hot. For sure though, a tapered pipe thread on a steel pipe can definitely strip and or fracture aluminum blocks. 

[WHNJ701 4,165]

time for a big ,giant, chrome stack with a flapper

[ebinmaine 69,230]

20 minutes ago, jabelman said:

time for a big ,giant, chrome stack with a flapper

~I~ agree... But it's my honey's tractor....

[Machineguy 877]

@953 nut 

 

Basically I was talking about putting a small screw tight against the conduit nut after it’s tightened flush to the block. Basically the little dot I crudely added to the pic is where a small set/grub screw could go in jamming the nut. Provided there’s enough room on the block. I hope that helps clear up my jibberish! Lol

Edited July 24, 2018 by Machineguy

[ebinmaine 69,230]

7 hours ago, jabelman said:

time for a big ,giant, chrome stack with a flapper

I'll try to remember to take a pic of the piece of chrome pipe I found at the recycling center.

No idea what it was in it's useful life.

Got weird fluted ends... When I saw it, exhaust stack was the first thing I thought of so I grabbed it.

[Pullstart 63,280]

17 hours ago, ebinmaine said:

 

I thought that would work too so I did put one on.

 

Thing is, the direction of loosening is also the direction that is in favor of gravity.

So when the motor got hot, the muffler just started to fall.

 

 

Sometimes exhaust manifold gasket instructions and other high-heat items say to tighten, then bring up to operating temp, then tighten.  I wonder if that conduit nut could get any more snug when it’s all good and hot?

[ebinmaine 69,230]

3 minutes ago, pullstart said:

 

 

Sometimes exhaust manifold gasket instructions and other high-heat items say to tighten, then bring up to operating temp, then tighten.  I wonder if that conduit nut could get any more snug when it’s all good and hot?

That's true that's true.

4 foot extension pipe should make that thing tight enough.